1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386 2387 2388 2389 2390 2391 2392 2393 2394 2395 2396 2397 2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637 2638 2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662 2663 2664 2665 2666 2667 2668 2669 2670 2671 2672 2673 2674 2675 2676 2677 2678 2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713 2714 2715 2716 2717 2718 2719 2720 2721 2722 2723 2724 2725 2726 2727 2728 2729 2730 2731 2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763 2764 2765 2766 2767 2768 2769 2770 2771 2772 2773 2774 2775 2776 2777 2778 2779 2780 2781 2782 2783 2784 2785 2786 2787 2788 2789 2790 2791 2792 2793 2794 2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818 2819 2820 2821 2822 2823 2824 2825 2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875 2876 2877 2878 2879 2880 2881 2882 2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902 2903 2904 2905 2906 2907 2908 2909 2910 2911 2912 2913 2914 2915 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 2931 2932 2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951 2952 2953 2954 2955 2956 2957 2958 2959 2960 2961 2962 2963 2964 2965 2966 2967 2968 2969 2970 2971 2972 2973 2974 2975 2976 2977 2978 2979 2980 2981 2982 2983 2984 2985 2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004 3005 3006 3007 3008 3009 3010 3011 3012 3013 3014 3015 3016 3017 3018 3019 3020 3021 3022 3023 3024 3025 3026 3027 3028 3029 3030 3031 3032 3033 3034 3035 3036 3037 3038 3039 3040 3041 3042 3043 3044 3045 3046 3047 3048 3049 3050 3051 3052 3053 3054 3055 3056 3057 3058 3059 3060 3061 3062 3063 3064 3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080 3081 3082 3083 3084 3085 3086 3087 3088 3089 3090 3091 3092 3093 3094 3095 3096 3097 3098 3099 3100 3101 3102 3103 3104 3105 3106 3107 3108 3109 3110 3111 3112 3113 3114 3115 3116 3117 3118 3119 3120 3121 3122 3123 3124 3125 3126 3127 3128 3129 3130 3131 3132 3133 3134 3135 3136 3137 3138 3139 3140 3141 3142 3143 3144 3145 3146 3147 3148 3149 3150 3151 3152 3153 3154 3155 3156 3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182 3183 3184 3185 3186 3187 3188 3189 3190 3191 3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210 3211 3212 3213 3214 3215 3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228 3229 3230 3231 3232 3233 3234 3235 3236 3237 3238 3239 3240 3241 3242 3243 3244 3245 3246 3247 3248 3249 3250 3251 3252 3253 3254 3255 3256 3257 3258 3259 3260 3261 3262 3263 3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275 3276 3277 3278 3279 3280 3281 3282 3283 3284 3285 3286 3287 3288 3289 3290 3291 3292 3293 3294 3295 3296 3297 3298 3299 3300 3301 3302 3303 3304 3305 3306 3307 3308 3309 3310 3311 3312 3313 3314 3315 3316 3317 3318 3319 3320 3321 3322 3323 3324 3325 3326 3327 3328 3329 3330 3331 3332 3333 3334 3335 3336 3337 3338 3339 3340 3341 3342 3343 3344 3345 3346 3347 3348 3349 3350 3351 3352 3353 3354 3355 3356 3357 3358 3359 3360 3361 3362 3363 3364 3365 3366 3367 3368 3369 3370 3371 3372 3373 3374 3375 3376 3377 3378 3379 3380 3381 3382 3383 3384 3385 3386 3387 3388 3389 3390 3391 3392 3393 3394 3395 3396 3397 3398 3399 3400 3401 3402 3403 3404 3405 3406 3407 3408 3409 3410 3411 3412 3413 3414 3415 3416 3417 3418 3419 3420 3421 3422 3423 3424 3425 3426 3427 3428 3429 3430 3431 3432 3433 3434 3435 3436 3437 3438 3439 3440 3441 3442 3443 3444 3445 3446 3447 3448 3449 3450 3451 3452 3453 3454 3455 3456 3457 3458 3459 3460 3461 3462 3463 3464 3465 3466 3467 3468 3469 3470 3471 3472 3473 3474 3475 3476 3477 3478 3479 3480 3481 3482 3483 3484 3485 3486 3487 3488 3489 3490 3491 3492 3493 3494 3495 3496 3497 3498 3499 3500 3501 3502 3503 3504 3505 3506 3507 3508 3509 3510 3511 3512 3513 3514 3515 3516 3517 3518 3519 3520 3521 3522 3523 3524 3525 3526 3527 3528 3529 3530 3531 3532 3533 3534 3535 3536 3537 3538 3539 3540 3541 3542 3543 3544 3545 3546 3547 3548 3549 3550 3551 3552 3553 3554 3555 3556 3557 3558 3559 3560 3561 3562 3563 3564 3565 3566 3567 3568 3569 3570 3571 3572 3573 3574 3575 3576 3577 3578 3579 3580 3581 3582 3583 3584 3585 3586 3587 3588 3589 3590 3591 3592 3593 3594 3595 3596 3597 3598 3599 3600 3601 3602 3603 3604 3605 3606 3607 3608 3609 3610 3611 3612 3613 3614 3615 3616 3617 3618 3619 3620 3621 3622 3623 3624 3625 3626 3627 3628 3629 3630 3631 3632 3633 3634 3635 3636 3637 3638 3639 3640 3641 3642 3643 3644 3645 3646 3647 3648 3649 3650 3651 3652 3653 3654
|
START-INFO-DIR-ENTRY
* chrony: (chrony). How to use chronyd and chronyc
* chronyd: (chrony)Starting chronyd. Reference for chronyd
* chronyc: (chrony)Running chronyc. Reference for chronyc
END-INFO-DIR-ENTRY
1 Introduction
**************
1.1 Overview
============
Chrony is a software package for maintaining the accuracy of computer
system clocks. It consists of a pair of programs :
* `chronyd'. This is a daemon which runs in background on the
system. It obtains measurements (e.g. via the network) of the
system's offset relative to other systems, and adjusts the system
time accordingly. For isolated systems, the user can periodically
enter the correct time by hand (using `chronyc'). In either case,
`chronyd' determines the rate at which the computer gains or loses
time, and compensates for this.
`chronyd' can also act as an NTP server, and provide a time-of-day
service to other computers. A typical set-up is to run `chronyd'
on a gateway computer that has a dial-up link to the Internet, and
use it to serve time to computers on a private LAN sitting behind
the gateway. The IP addresses that can act as clients of
`chronyd' can be tightly controlled. The default is no client
access.
* `chronyc'. This is a command-line driven control and monitoring
program. An administrator can use this to fine-tune various
parameters within the daemon, add or delete servers etc whilst the
daemon is running.
The IP addresses from which `chronyc' clients may connect can be
tightly controlled. The default is just the computer that
`chronyd' itself is running on.
1.2 Acknowledgements
====================
The `chrony' suite makes use of the algorithm known as _RSA Data
Security, Inc. MD5 Message-Digest Algorithm_ for authenticating
messages between different machines on the network.
In writing the `chronyd' program, extensive use has been made of
RFC1305, written by David Mills. I have occasionally referred to the
`xntp' suite's source code to check details of the protocol that the
RFC did not make absolutely clear. The core algorithms in `chronyd'
are all completely distinct from `xntp', however.
1.3 Availability
================
1.3.1 Getting the software
--------------------------
Links on the chrony home page
(http://chrony.sunsite.dk/download.php) describe how to obtain the
software.
1.3.2 Platforms
---------------
Although most of the program is portable between Unix-like systems,
there are parts that have to be tailored to each specific vendor's
system. These are the parts that interface with the operating system's
facilities for adjusting the system clock; different operating systems
may provide different function calls to achieve this, and even where
the same function is used it may have different quirks in its behaviour.
The software is known to work in the following environments:
* Linux/i386 and Linux/ppc. The software is known to work on Linux
2.0.x, 2.2.x and 2.4.x. Prior to 2.0.31, the real time clock
can't be used.
* NetBSD
* BSD/386
* Solaris 2.3/2.5/2.5.1/2.6/2.7/2.8 on Sparc (Sparc 20, Ultrasparc)
and i386
* SunOS 4.1.4 on Sparc 2 and Sparc20.
Closely related systems may work too, but they have not been tested.
Porting the software to other system (particularly to those
supporting an `adjtime' system call) should not be difficult, however it
requires access to such systems to test out the driver.
1.4 Relationship to other software packages
===========================================
1.4.1 xntpd
-----------
The `reference' implementation of the Network Time Protocol is the
program `xntpd', available via The NTP home page
(http://www.eecis.udel.edu/~ntp).
`xntpd' is designed to support all the operating modes defined by
RFC1305, and has driver support for a large number of reference clocks
(such as GPS receivers) that can be connected directly to a computer,
thereby providing a so-called 'stratum 1' server.
Things `chronyd' can do that `xntpd' can't:
* `chronyd' can perform usefully in an environment where access to
the time reference is intermittent. `chronyd' estimates _both_
the current time offset _and_ the rate at which the computer's
clock gains or loses time, and can use that rate estimate to trim
the clock after the reference disappears. `xntpd' corrects any
time offset by speeding up and slowing down the computer clock, and
so could be left with a significant rate error if the reference
disappears whilst it is trying to correct a big offset.
* `chronyd' provides support for isolated networks whether the only
method of time correction is manual entry (e.g. by the
administrator looking at a clock). `chronyd' can look at the
errors corrected at different updates to work out the rate at
which the computer gains or loses time, and use this estimate to
trim the computer clock subsequently.
* `chronyd' provides support to work out the gain or loss rate of the
`real-time clock', i.e. the clock that maintains the time when the
computer is turned off. It can use this data when the system
boots to set the system time from a corrected version of the
real-time clock. These real-time clock facilities are only
available on certain releases of Linux, so far.
* The `xntpd' program is supported by other programs to carry out
certain functions. `ntpdate' is used to provide an initial
correction to the system clock based on a `one-shot' sampling of
other NTP servers. `tickadj' is used to adjust certain operating
system parameters to make `xntpd' work better. All this
functionality is integrated into `chronyd'.
Things `xntpd' can do that `chronyd' can't:
* `xntpd' supports a range of different hardware reference clocks
(GPS, atomic etc) that can be connected to a computer to provide a
`stratum-1' server. `chronyd' does not support any such hardware
_yet_; I don't have access to any to do any development work.
However, the software architecture should allow such equipment to
be interfaced at a later date.
* `xntpd' supports effectively all of RFC1305, including broadcast /
multicast clients, leap seconds, and extra encryption schemes for
authenticating data packets.
* `xntpd' has been ported to more types of computer / operating
system (so far).
* xntpd is designed to work solely with integer arithmetic (i.e.
does not require floating point support from its host).
1.4.2 timed
-----------
`timed' is a program that is part of the BSD networking suite. It
uses broadcast packets to find all machines running the daemon within a
subnet. The machines elect a master which periodically measures the
system clock offsets of the other computers using ICMP timestamps.
Corrections are sent to each member as a result of this process.
Problems that may arise with `timed' are :
* Because it uses broadcasts, it is not possible to isolate its
functionality to a particular group of computers; there is a risk
of upsetting other computers on the same network (e.g. where a
whole company is on the same subnet but different departments are
independent from the point of view of administering their
computers.)
* The update period appears to be 10 minutes. Computers can build up
significant offsets relative to each other in that time. If a
computer can estimate its rate of drift it can keep itself closer
to the other computers between updates by adjusting its clock
every few seconds. `timed' does not seem to do this.
* `timed' does not have any integrated capability for feeding
real-time into its estimates, or for estimating the average rate
of time loss/gain of the machines relative to real-time (unless
one of the computers in the group has access to an external
reference and is always appointed as the `master').
`timed' does have the benefit over `chronyd' that for isolated
networks of computers, they will track the `majority vote' time. For
such isolated networks, `chronyd' requires one computer to be the
`master' with the others slaved to it. If the master has a particular
defective clock, the whole set of computers will tend to slip relative
to real time (but they _will_ stay accurate relative to one another).
1.5 Distribution rights and (lack of) warranty
==============================================
Chrony may be distributed in accordance with the GNU General Public
License version 2, reproduced in *Note GPL::.
1.6 Bug reporting and suggestions
=================================
If you think you've found a bug in chrony, or have a suggestion,
please let me know. My primary current email address is
<rc@rc0.org.uk>. If that fails, you could try finding me through one
of the chrony mailing lists, or by looking up my name on a search
engine.
I can't promise a timescale to fix a bug; it depends a lot on the
how complex the bug is to track down, as I have a lot of other calls on
my time : 2 young children, my job, and indeed other free/open source
software projects. However, I do intend to look into problems when
time allows.
Another source of information to try is the chrony users mailing
list. You can join this by sending an empty message to
<chrony-users-subscribe@sunsite.dk>. Only subscribers can post to the
list.
When you are reporting a bug, please send me all the information you
can. Unfortunately, chrony has proven to be one of those programs
where it is very difficult to reproduce bugs in a different
environment. So I may have to interact with you quite a lot to obtain
enough extra logging and tracing to pin-point the problem in some
cases. Please be patient and plan for this!
Of course, if you can debug the problem yourself and send me a
source code patch to fix it, I will be very grateful!
1.7 Contributions
=================
Although chrony is now a fairly mature and established project,
there are still areas that could be improved. If you can program in C
and have some expertise in these areas, you might be able to fill the
gaps.
Particular areas I know need addressing are :
1. Porting to other Unices
This involves creating equivalents of sys_solaris.c, sys_linux.c
etc for the new system. Note, the Linux driver has been reported
as working on a range of different architectures (Alpha, Sparc,
MIPS as well as x86 of course).
2. Porting to Windows NT
I did a small amount of work on this under Cygwin. Only the
sorting out of the include files has really been achieved so far.
The two main areas still to address are
1. The system clock driver.
2. How to make chronyd into an NT service (i.e. what to replace
fork(), setsid() etc with so that chronyd can be
automatically started in the system bootstrap.
3. Hardware clock support
4. Automation of the trimrtc and writertc mechanisms
Currently, the RTC trimming mechanism is a manual operation,
because there has to be a reasonable guarantee that the system
will stay up for a reasonable length of time afterwards. (If it
is shut down too soon, a poor characterisation of the RTC drift
rate will be stored on disc, giving a bad system clock error when
the system is next booted.)
To make chrony more automated for the non-expert user, it would be
useful if this problem could be avoided so that trimrtc could be
done automatically (e.g. in a crontab, or as part of the ip-up or
ip-down scripts.)
2 Installation
**************
The software is distributed as source code which has to be compiled.
The source code is supplied in the form of a gzipped tar file, which
unpacks to a subdirectory identifying the name and version of the
program.
After unpacking the source code, change directory into it, and type
./configure
This is a shell script that automatically determines the system type.
There is a single optional parameter, `--prefix' which indicates the
directory tree where the software should be installed. For example,
./configure --prefix=/opt/free
will install the `chronyd' daemon into /opt/free/sbin and the
chronyc control program into /opt/free/bin. The default value for the
prefix is /usr/local.
The configure script assumes you want to use gcc as your compiler.
If you want to use a different compiler, you can configure this way:
CC=cc CFLAGS=-O ./configure --prefix=/opt/free
for Bourne-family shells, or
setenv CC cc
setenv CFLAGS -O
./configure --prefix=/opt/free
for C-family shells.
If the software cannot (yet) be built on your system, an error
message will be shown. Otherwise, the files `options.h' and `Makefile'
will be generated.
By default, chronyc will be built to make use of the readline
library. If you don't want this, specify the -disable-readline flag to
configure. If you have readline and/or ncurses installed in a
non-standard location, please refer to *note readline support:: for
information.
Now type
make
to build the programs.
If you want to build the manual in plain text, HTML and info
versions, type
make docs
Once the programs have been successfully compiled, they need to be
installed in their target locations. This step normally needs to be
performed by the superuser, and requires the following command to be
entered.
make install
This will install the binaries, plain text manual and manpages.
To install the HTML and info versions of the manual as well, enter
the command
make install-docs
If you want chrony to appear in the top level info directory
listing, you need to run the `install-info' command manually after this
step. `install-info' takes 2 arguments. The first is the path to the
`chrony.info' file you have just installed. This will be the argument
you gave to -prefix when you configured (`/usr/local' by default), with
`/info/chrony.info' on the end. The second argument is the location of
the file called `dir'. This will typically be `/usr/info/dir'. So the
typical command line would be
install-info /usr/local/info/chrony.info /usr/info/dir
Now that the software is successfully installed, the next step is to
set up a configuration file. The contents of this depend on the
network environment in which the computer operates. The Debian package
installs a simple configuration file suitable for a dial-up pc. You
should edit it to suit your situation. Typical scenarios are described
in the following section of the document.
2.1 Support for the readline library
====================================
By default, chronyc is built to make use of the readline library.
This allows you to use the cursor keys to replay and edit old commands.
If you don't want to use readline (in which case chronyc will use a
minimal command line interface), invoke configure like this:
./configure --disable-readline other-options...
If you have readline and/or ncurses installed in locations that
aren't normally searched by the compiler and linker, you need extra
options if you want readline to be used:
`--with-readline-includes=directory_name'
This defines the name of the directory above the one where
`readline.h' is. `readline.h' is assumed to be in a `readline'
subdirectory of the named directory.
`--with-readline-library=directory_name'
This defines the directory containing the `libreadline.a' or
`libreadline.so' file.
`--with-ncurses-library=directory_name'
This defines the directory containing the `libncurses.a' or
`libncurses.so' file.
2.2 Extra options for package builders
======================================
The configure and make procedures have some extra options that may
be useful if you are building a distribution package for chrony.
The -infodir=DIR option to configure specifies a different install
directory for the info files. This overrides the `info' subdirectory
of the argument to the -prefix option. For example, you might use
./configure --prefix=/usr --infodir=/usr/share/info
The -mandir=DIR option to configure specifies a different install
directory for the man pages. This overrides the `man' subdirectory of
the argument to the -prefix option.
./configure --prefix=/usr --infodir=/usr/share/info --mandir=/usr/share/man
to set both options together.
The final option is the DESTDIR option to the make command. For
example, you could use the commands
./configure --prefix=/usr --infodir=/usr/share/info --mandir=/usr/share/man
make all docs
make install DESTDIR=./tmp
cd tmp
tar cvf - . | gzip -9 > chrony.tar.gz
to build a package. When untarred within the root directory, this
will install the files to the intended final locations.
3 Typical operating scenarios
*****************************
3.1 Computers connected to the internet
=======================================
In this section we discuss how to configure chrony for computers that
have permanent connections to the internet (or to any network
containing true NTP servers which ultimately derive their time from a
reference clock).
To operate in this mode, you will need to know the names of the NTP
server machines you wish to use. You may be able to find names of
suitable servers by one of the following methods:
* Your institution may already operate servers on its network.
Contact your system administrator to find out.
* Your ISP probably has one or more NTP servers available for its
customers.
* Somewhere under the NTP homepage there is a list of public stratum
1 and stratum 2 servers. You should find one or more servers that
are near to you -- check that their access policy allows you to
use their facilities.
Assuming that you have found some servers, you need to set up a
configuration file to run chrony. The (compiled-in) default location
for this file is `/etc/chrony.conf'. In the Debian package the
configuration files are in the directory `/etc/chrony'. Assuming that
your ntp servers are called `a.b.c' and `d.e.f', your `chrony.conf'
file could contain as a minimum
server a.b.c
server d.e.f
server g.h.i
However, you will probably want to include some of the other
directives described later. The following directives will be
particularly useful : `driftfile', `commandkey', `keyfile'. The
smallest useful configuration file would look something like
server a.b.c
server d.e.f
server g.h.i
keyfile /etc/chrony.keys
commandkey 1
driftfile /etc/chrony.drift
3.2 Infrequent connection to true NTP servers
=============================================
In this section we discuss how to configure chrony for computers that
have occasional connections to the internet.
3.2.1 Setting up the configuration file for infrequent connections
------------------------------------------------------------------
As in the previous section, you will need access to NTP servers on
the internet. The same remarks apply for how to find them.
In this case, you will need some additional configuration to tell
`chronyd' when the connection to the internet goes up and down. This
saves the program from continuously trying to poll the servers when
they are inaccessible.
Again, assuming that your ntp servers are called `a.b.c' and
`d.e.f', your `chrony.conf' file would need to contain something like
server a.b.c
server d.e.f
server g.h.i
However, the following issues need to be addressed:
1. Your computer probably doesn't have DNS access whilst offline to
turn the machine names into IP addresses.
2. Your computer will keep trying to contact the servers to obtain
timestamps, even whilst offline. If you operate a dial-on-demand
system, things are even worse, because the link to the internet
will keep getting established.
For this reason, it would be better to specify this part of your
configuration file in the following way:
server 1.2.3.4 offline
server 5.6.7.8 offline
server 9.10.11.12 offline
Because numeric IP addresses have been used, the first problem is
overcome. The `offline' keyword indicates that the servers start in an
offline state, and that they should not be contacted until `chronyd'
receives notification that the link to the internet is present.
An alternative is to use the names of the NTP servers, and put
entries for them into your `/etc/hosts' file. This will be OK as long
as `files' comes before `dns' in the `hosts' line of the
`/etc/nsswitch.conf' file.
In order to notify `chronyd' of the presence of the link, you will
need to be able to log in to it with the program chronyc. To do this,
`chronyd' needs to be configured with an administrator password. The
Debian package puts a randomly generated key in
`/etc/chrony/chrony.keys'. You should change it. To set up an
administrator password, you can create a file `/etc/chrony.keys'
containing a single line
1 xyzzy
and add the following line to `/etc/chrony.conf' (the order of the
lines does not matter)
commandkey 1
The smallest useful configuration file would look something like
server 1.2.3.4 offline
server 5.6.7.8 offline
server 9.10.11.12 offline
keyfile /etc/chrony.keys
commandkey 1
driftfile /etc/chrony.drift
The next section describes how to tell `chronyd' when the internet
link goes up and down.
3.2.2 How to tell chronyd when the internet link is available.
--------------------------------------------------------------
To use this option, you will need to configure a command key in
`chronyd's' configuration file `/etc/chrony.conf', as described in the
previous section.
To tell `chronyd' when to start and finish sampling the servers, the
`online' and `offline' commands of chronyc need to be used. To give an
example of their use, we assume that `pppd' is the program being used
to connect to the internet, and that chronyc has been installed at its
default location `/usr/local/bin/chronyc'. We also assume that the
command key has been set up as described in the previous section.
In the file `/etc/ppp/ip-up' we add the command sequence
/usr/local/bin/chronyc <<EOF
password xyzzy
online
EOF
and in the file `/etc/ppp/ip-down' we add the sequence
/usr/local/bin/chronyc <<EOF
password xyzzy
offline
EOF
The Debian package puts scripts similar to those above in the
directories `/etc/ppp/ip-up.d' and `/etc/ppp/ip-down.d'.
`chronyd's' polling of the servers will now only occur whilst the
machine is actually connected to the Internet.
3.3 Isolated networks
=====================
In this section we discuss how to configure chrony for computers that
never have network conectivity to any computer which ultimately derives
its time from a reference clock.
In this situation, one computer is selected to be the master
timeserver. The other computers are either direct clients of the
master, or clients of clients.
The rate value in the master's drift file needs to be set to the
average rate at which the master gains or loses time. `chronyd'
includes support for this, in the form of the `manual' directive in the
configuration file and the `settime' command in the `chronyc' program.
If the master is rebooted, `chronyd' can re-read the drift rate from
the drift file. However, the master has no accurate estimate of the
current time. To get around this, the system can be configured so that
the master can initially set itself to a `majority-vote' of selected
clients' times; this allows the clients to `flywheel' the master across
its outage.
A typical configuration file for the master (called `master') might
be (assuming the clients are in the 192.168.165.x subnet and that the
master's address is 192.168.169.170)
driftfile /etc/chrony.drift
commandkey 25
keyfile /etc/chrony.keys
initstepslew 10 client1 client3 client6
local stratum 8
manual
allow 192.168.165
For the clients that have to resynchronise the master when it
restarts, the configuration file might be
server master
driftfile /etc/chrony.drift
logdir /var/log/chrony
log measurements statistics tracking
keyfile /etc/chrony.keys
commandkey 24
local stratum 10
initstepslew 20 master
allow 192.168.169.170
The rest of the clients would be the same, except that the `local'
and `allow' directives are not required.
3.4 The home PC with a dial-up connection
=========================================
3.4.1 Assumptions/how the software works
----------------------------------------
This section considers the home computer which has a dial-up
connection. It assumes that Linux is run exclusively on the computer.
Dual-boot systems may work; it depends what (if anything) the other
system does to the system's real-time clock.
Much of the configuration for this case is discussed earlier (*note
Infrequent connection::). This section addresses specifically the case
of a computer which is turned off between 'sessions'.
In this case, `chronyd' relies on the computer's real-time clock
(RTC) to maintain the time between the periods when it is powered up.
The arrangement is shown in the figure below.
trim if required PSTN
+---------------------------+ +----------+
| | | |
v | | |
+---------+ +-------+ +-----+ +---+
| System's| measure error/ |chronyd| |modem| |ISP|
|real-time|------------------->| |-------| | | |
| clock | drift rate +-------+ +-----+ +---+
+---------+ ^ |
| | |
+---------------------------+ --o-----o---
set time at boot up |
+----------+
|NTP server|
+----------+
When the computer is connected to the Internet (via the modem),
`chronyd' has access to external NTP servers which it makes
measurements from. These measurements are saved, and straight-line fits
are performed on them to provide an estimate of the computer's time
error and rate of gaining/losing time.
When the computer is taken offline from the Internet, the best
estimate of the gain/loss rate is used to free-run the computer until
it next goes online.
Whilst the computer is running, `chronyd' makes measurements of the
real-time clock (RTC) (via the `/dev/rtc' interface, which must be
compiled into the kernel). An estimate is made of the RTC error at a
particular RTC second, and the rate at which the RTC gains or loses time
relative to true time.
The RTC is fully supported in 2.2 and 2.4 kernels.
For kernels in the 2.0 series prior to 2.0.32, the kernel was set up
to trim the RTC every 11 minutes. This would be disasterous for
`chronyd' - there is no reliable way of synchronising with this
trimming. For this reason, `chronyd' only supports the RTC in 2.0
kernels from v2.0.32 onwards.
When the computer is powered down, the measurement histories for all
the NTP servers are saved to files (if the `dumponexit' directive is
specified in the configuration file), and the RTC tracking information
is also saved to a file (if the `rtcfile' directive has been
specified). These pieces of information are also saved if the `dump'
and `writertc' commands respectively are issued through `chronyc'.
When the computer is rebooted, `chronyd' reads the current RTC time
and the RTC information saved at the last shutdown. This information is
used to set the system clock to the best estimate of what its time would
have been now, had it been left running continuously. The measurement
histories for the servers are then reloaded.
The next time the computer goes online, the previous sessions'
measurements can contribute to the line-fitting process, which gives a
much better estimate of the computer's gain/loss rate.
One problem with saving the measurements and RTC data when the
machine is shut down is what happens if there is a power failure; the
most recent data will not be saved. Although `chronyd' is robust enough
to cope with this, some performance may be lost. (The main danger
arises if the RTC has been changed during the session, with the
`trimrtc' command in `chronyc'. Because of this, `trimrtc' will make
sure that a meaningful RTC file is saved out after the change is
completed).
The easiest protection against power failure is to put the `dump'
and `writertc' commands in the same place as the `offline' command is
issued to take `chronyd' offline; because `chronyd' free-runs between
online sessions, no parameters will change significantly between going
offline from the Internet and any power failure.
A final point regards home computers which are left running for
extended periods and where it is desired to spin down the hard disc
when it is not in use (e.g. when not accessed for 15 minutes).
`chronyd' has been planned so it supports such operation; this is the
reason why the RTC tracking parameters are not saved to disc after
every update, but only when the user requests such a write, or during
the shutdown sequence. The only other facility that will generate
periodic writes to the disc is the `log rtc' facility in the
configuration file; this option should not be used if you want your
disc to spin down.
3.4.2 Typical configuration files.
----------------------------------
To illustrate how a dial-up home computer might be configured,
example configuration files are shown in this section.
For the `/etc/chrony.conf' file, the following can be used as an
example. _NOTE : The `server' directives are only applicable to
customers of Demon Internet; users of other ISPs will need to use their
own ISP's NTP servers or public NTP servers._
server 158.152.1.65 minpoll 5 maxpoll 10 maxdelay 0.4 offline
server 158.152.1.76 minpoll 5 maxpoll 10 maxdelay 0.4 offline
server 194.159.253.2 minpoll 5 maxpoll 10 maxdelay 0.4 offline
logdir /var/log/chrony
log statistics measurements tracking
driftfile /etc/chrony.drift
keyfile /etc/chrony.keys
commandkey 25
maxupdateskew 100.0
dumponexit
dumpdir /var/log/chrony
rtcfile /etc/chrony.rtc
With Freeserve as the ISP, I use the following server lines :
server 194.152.64.68 minpoll 5 maxpoll 10 maxdelay 0.4 offline
server 194.152.64.35 minpoll 5 maxpoll 10 maxdelay 0.4 offline
server 194.152.64.34 minpoll 5 maxpoll 10 maxdelay 0.4 offline
I use `pppd' for connecting to my ISP. This runs two scripts
`/etc/ppp/ip-up' and `/etc/ppp/ip-down' when the link goes online and
offline respectively.
The relevant part of the `/etc/ppp/ip-up' file is (with a dummy
password)
/usr/local/bin/chronyc <<EOF
password xxxxxxxx
online
EOF
and the relevant part of the `/etc/ppp/ip-down' script is
/usr/local/bin/chronyc <<EOF
password xxxxxxxx
offline
dump
writertc
EOF
(Because they have to contain the administrator password, it would be
desirable to make the files readable only by root on a multiuser
machine).
To start `chronyd' during the boot sequence, I have the following in
`/etc/rc.d/rc.local' (this is a Slackware system)
if [ -f /usr/local/sbin/chronyd -a -f /etc/chrony.conf ]; then
/usr/local/sbin/chronyd -r -s
echo "Start chronyd"
fi
The Debian package puts a script which handles this and shutdown in
`/etc/init.d/chrony'.
The placement of this command may be important on some systems. In
particular, `chronyd' may need to be started several seconds (about 10
as a minimum) before any software that depends on the system clock not
jumping or moving backwards, depending on the directives in `chronyd's'
configuration file.
For the system shutdown, `chronyd' should receive a SIGTERM several
seconds before the final SIGKILL; the SIGTERM causes the measurement
histories and RTC information to be saved out. There should be no need
to add anything to the shutdown sequence, unless (as my system had)
there is no pause between the SIGTERM and SIGKILL being delivered to the
remaining processes. So if you find something like
killall5 -15
killall5 -9
in your `/etc/rc.d/rc.0' script, you will need to insert a sleep,
e.g.
killall5 -15
sleep 5
killall5 -9
Otherwise, `chronyd' will not always save information on shutdown,
which could be a problem if you don't use `dump' and `writertc' when
you go offline.
3.5 Other important configuration options
=========================================
The most common option to include in the configuration file is the
`driftfile' option. One of the major tasks of `chronyd' is to work out
how fast or how slow the system clock runs relative to real time - e.g.
in terms of seconds gained or lost per day. Measurements over a long
period are usually required to refine this estimate to an acceptable
degree of accuracy. Therefore, it would be bad if `chronyd' had to
work the value out each time it is restarted, because the system clock
would not run so accurately whilst the determination is taking place.
To avoid this problem, `chronyd' allows the gain or loss rate to be
stored in a file, which can be read back in when the program is
restarted. This file is called the drift file, and might typically be
stored in `/etc/chrony.drift'. By specifying an option like the
following
driftfile /etc/chrony.drift
in the configuration file (`/etc/chrony.conf'), the drift file
facility will be activated.
4 Usage reference
*****************
4.1 Starting chronyd
====================
If `chronyd' has been installed to its default location
`/usr/local/sbin/chronyd', starting it is simply a matter of entering
the command
/usr/local/sbin/chronyd
The Debian package uses `/usr/sbin/chronyd'.
Information messages and warnings will be logged to syslog.
The command line options supported are as follows:
`-d'
When run in this mode, the program will not detach itself from the
terminal, and all messages will be sent to the terminal instead of
to syslog.
`-f <conf-file>'
This option can be used to specify an alternate location for the
configuration file (default `/etc/chrony.conf').
`-r'
This option will reload sample histories for each of the servers
being used. These histories are created by using the `dump'
command in `chronyc', or by setting the `dumponexit' directive in
the configuration file. This option is useful if you want to stop
and restart `chronyd' briefly for any reason, e.g. to install a new
version. However, it only makes sense on systems where the kernel
can maintain clock compensation whilst not under `chronyd's'
control. The only version where this happens so far is Linux. On
systems where this is not the case, e.g. Solaris and SunOS the
option should not be used.
`-s'
This option will set the system clock from the computer's real-time
clock. This is analogous to supplying the `-s' flag to the
`/sbin/clock' program during the Linux boot sequence.
Support for real-time clocks is limited at present - the criteria
are described in the section on the `rtcfile' directive (*note
rtcfile directive::).
If `chronyd' cannot support the real time clock on your computer,
this option cannot be used and a warning message will be logged to
the syslog.
If used in conjunction with the `-r' flag, `chronyd' will attempt
to preserve the old samples after setting the system clock from
the real time clock. This can be used to allow `chronyd' to
perform long term averaging of the gain or loss rate across system
reboots, and is useful for dial-up systems that are shut down when
not in use. For this to work well, it relies on `chronyd' having
been able to determine accurate statistics for the difference
between the real time clock and system clock last time the
computer was on.
`-v'
This option displays `chronyd's' version number to the terminal and
exits.
On systems that support an `/etc/rc.local' file for starting
programs at boot time, `chronyd' can be started from there.
On systems with a System V style initialisation (e.g. Solaris), a
suitable start/stop script might be as shown below. This might be
placed in the file `/etc/rc2.d/S83chrony'.
#!/bin/sh
# This file should have uid root, gid sys and chmod 744
#
killproc() { # kill the named process(es)
pid=`/usr/bin/ps -e |
/usr/bin/grep -w $1 |
/usr/bin/sed -e 's/^ *//' -e 's/ .*//'`
[ "$pid" != "" ] && kill $pid
}
case "$1" in
'start')
if [ -f /opt/free/sbin/chronyd -a -f /etc/chrony.conf ]; then
/opt/free/sbin/chronyd
fi
;;
'stop')
killproc chronyd
;;
*)
echo "Usage: /etc/rc2.d/S83chrony { start | stop }"
;;
esac
(In both cases, you may want to bear in mind that `chronyd' can step
the time when it starts. There may be other programs started at boot
time that could be upset by this, so you may need to consider the
ordering carefully. However, `chronyd' will need to start after
daemons providing services that it may require, e.g. the domain name
service.)
4.2 The chronyd configuration file
==================================
The configuration file is normally called `/etc/chrony.conf'; in
fact, this is the compiled-in default. However, other locations can be
specified with a command line option.
Each command in the configuration file is placed on a separate line.
The following sections describe each of the commands in turn. The
directives can occur in any order in the file.
4.2.1 Comments in the configuration file
----------------------------------------
The configuration file may contain comment lines. A comment line is
any line that starts with zero or more spaces followed by any one of
the following characters:
* !
* ;
* #
* %
Any line with this format will be ignored.
4.2.2 acquisitionport
---------------------
`chronyd' uses a separate client-side port for the rapid-fire
measurements requested with the `initstepslew' directive (*note
initstepslew directive::). Normally, that port is chosen arbitrarily
by the operating system. However, you can use `acquisitionport' to
explicitly specify a port. This may be useful for getting through
firewalls.
Do not make acquisition and regular NTP service (*note port
directive::) use the same port.
An example of the `acquisitionport' command is
acquisitionport 1123
This would change the port used for rapid queries to udp/1123. You
could then persuade the firewall administrator to let that port through.
4.2.3 allow
-----------
The `allow' command is used to designate a particular subnet from
which NTP clients are allowed to access the computer as an NTP server.
The default is that no clients are allowed access, i.e. `chronyd'
operates purely as an NTP client. If the `allow' directive is used,
`chronyd' will be both a client of its servers, and a server to other
clients.
Examples of use of the command are as follows:
allow foo.bar.com
allow 1.2
allow 3.4.5
allow 6.7.8/22
allow 6.7.8.9/22
allow
The first command allows the named node to be an NTP client of this
computer. The second command allows any node with an IP address of the
form 1.2.x.y (with x and y arbitrary) to be an NTP client of this
computer. Likewise, the third command allows any node with an IP
address of the form 3.4.5.x to have client NTP access. The fourth and
fifth forms allow access from any node with an IP address of the form
6.7.8.x, 6.7.9.x, 6.7.10.x or 6.7.11.x (with x arbitrary), i.e. the
value 22 is the number of bits defining the specified subnet. (In the
fifth form, the final byte is ignored). The sixth form allows access
by any node on the entire Internet.
A second form of the directive, `allow all', has a greater effect,
depending on the ordering of directives in the configuration file. To
illustrate the effect, consider the two examples
allow 1.2.3.4
deny 1.2.3
allow 1.2
and
allow 1.2.3.4
deny 1.2.3
allow all 1.2
In the first example, the effect is the same regardles of what order
the three directives are given in. So the 1.2.x.y subnet is allowed
access, except for the 1.2.3.x subnet, which is denied access, however
the host 1.2.3.4 is allowed access.
In the second example, the `allow all 1.2' directives overrides the
effect of _any_ previous directive relating to a subnet within the
specified subnet. Within a configuration file this capability is
probably rather moot; however, it is of greater use for reconfiguration
at run-time via `chronyc' (*note allow all command::).
Note, if the `initstepslew' directive (*note initstepslew
directive::) is used in the configuration file, each of the computers
listed in that directive must allow client access by this computer for
it to work.
4.2.4 bindaddress
-----------------
The bindaddress allows you to restrict the network interface to which
chronyd will listen for NTP packets. This provides an additional level
of access restriction above that available through the 'deny' mechanism.
Suppose you have a local ethernet with addresses in the 192.168.1.0
subnet together with a dial-up connection. The ethernet interface's IP
address is 192.168.1.1. Suppose (for some reason) you want to block all
access through the dialup connection (note, this will even block replies
from servers on the dialup side, so you will not be able to synchronise
to an external source). You could add the line
bindaddress 192.168.1.1
to the configuration file.
This directive affects NTP (UDP port 123) packets. If no
`bindcmdaddress' directive is present, the address supplied by
`bindaddress' will be used to control binding of the command socket
(UDP port 323) as well.
The `bindaddress' directive has been found to cause problems when
used on computers that need to pass NTP traffic over multiple network
interfaces (e.g. firewalls). It is, therefore, not particularly
useful. Use of the `allow' and `deny' directives together with a
network firewall is more likely to be successful.
4.2.5 bindcmdaddress
--------------------
The bindcmdaddress allows you to restrict the network interface to
which chronyd will listen for command packets (issued by chronyc).
Suppose you have a local ethernet with addresses in the 192.168.1.0
subnet together with a dial-up connection. The ethernet interface's IP
address is 192.168.1.1. Suppose you want to block all access through
the dialup connection. You could add the line
bindcmdaddress 192.168.1.1
to the configuration file.
The `bindcmdaddress' directive has been found to cause problems when
used on computers that need to pass command traffic over multiple
network interfaces. It is, therefore, not particularly useful. Use of
the `cmdallow' and `cmddeny' directives together with a network firewall
is more likely to be successful.
4.2.6 broadcast
---------------
The `broadcast' directive is used to declare a broadcast address to
which chronyd should send packets in NTP broadcast mode (i.e. make
chronyd act as a broadcast server). Broadcast clients on that subnet
will be able to synchronise.
The syntax is as follows
broadcast 30 192.168.1.255
broadcast 60 192.168.2.255 12123
In the first example, the destination port defaults to 123/udp (the
normal NTP port). In the second example, the destionation port is
specified as 12123. The first parameter in each case (30 or 60
respectively) is the interval in seconds between broadcast packets
being sent. The second parameter in each case is the broadcast address
to send the packet to. This should correspond to the broadcast address
of one of the network interfaces on the computer where chronyd is
running.
You can have more than 1 `broadcast' directive if you have more than
1 network interface onto which you wish to send NTP broadcast packets.
Chronyd itself cannot currently act as a broadcast client; it must
always be configured as a point-to-point client by defining specific
NTP servers and peers. This broadcast server feature is intended for
providing a time source to other NTP software (e.g. various MS Windows
clients).
If xntpd is used as the broadcast client, it will try to use a
point-to-point client/server NTP access to measure the round-trip
delay. Thus, the broadcast subnet should also be the subject of an
`allow' directive (*note allow directive::).
4.2.7 cmdallow
--------------
This is similar to the `allow' directive (*note allow directive::),
except that it allows control access (rather than NTP client access) to
a particular subnet or host. (By 'control access' is meant that
chronyc can be run on those hosts and successfully connect to chronyd
on this computer.)
The syntax is identical to the `allow' directive.
There is also a `cmdallow all' directive with similar behaviour to
the `allow all' directive (but applying to control access in this case,
of course).
4.2.8 cmddeny
-------------
This is similar to the `cmdallow' directive (*note cmdallow
directive::), except that it denies control access to a particular
subnet or host, rather than allowing it.
The syntax is identical.
There is also a `cmddeny all' directive with similar behaviour to the
`cmdallow all' directive.
4.2.9 commandkey
----------------
The commandkey command is used to set the key number used for
authenticating user commands via the chronyc program at run time. This
allows certain actions of the chronyc program to be restricted to
administrators.
An example of the commandkey command is
commandkey 20
In the key file (see the keyfile command) there should be a line of
the form
20 foobar
When running the chronyc program to perform run-time configuration,
the command
password foobar
must be entered before any commands affecting the operation of the
daemon can be entered.
4.2.10 cmdport
--------------
The `cmdport' directive allows the port that is used for run-time
command and monitoring (via the program `chronyc') to be altered from
its default (323/udp).
An example shows the syntax
cmdport 257
This would make `chronyd' use 257/udp as its command port.
(`chronyc' would need to be run with the `-p 257' switch to
inter-operate correctly).
4.2.11 deny
-----------
This is similar to the `allow' directive (*note allow directive::),
except that it denies NTP client access to a particular subnet or host,
rather than allowing it.
The syntax is identical.
There is also a `deny all' directive with similar behaviour to the
`allow all' directive.
4.2.12 driftfile
----------------
One of the main activities of the `chronyd' program is to work out
the rate at which the system clock gains or loses time relative to real
time.
Whenever `chronyd' computes a new value of the gain/loss rate, it is
desirable to record it somewhere. This allows `chronyd' to begin
compensating the system clock at that rate whenever it is restarted,
even before it has had a chance to obtain an equally good estimate of
the rate during the new run. (This process may take many minutes, at
least).
The driftfile command allows a file to be specified into which
`chronyd' can store the rate information. Two parameters are recorded
in the file. The first is the rate at which the system clock gains or
loses time, expressed in parts per million, with gains positive.
Therefore, a value of 100.0 indicates that when the system clock has
advanced by a second, it has gained 100 microseconds on reality (so the
true time has only advanced by 999900 microseconds). The second is an
estimate of the error bound around the first value in which the true
rate actually lies.
An example of the driftfile command is
driftfile /etc/chrony.drift
4.2.13 dumpdir
--------------
To compute the rate of gain or loss of time, `chronyd' has to store
a measurement history for each of the time sources it uses.
Certain systems (so far only Linux) have operating system support for
setting the rate of gain or loss to compensate for known errors. (On
other systems, `chronyd' must simulate such a capability by
periodically slewing the system clock forwards or backwards by a
suitable amount to compensate for the error built up since the previous
slew).
For such systems, it is possible to save the measurement history
across restarts of `chronyd' (assuming no changes are made to the system
clock behaviour whilst it is not running). If this capability is to be
used (via the dumponexit command in the configuration file, or the dump
command in chronyc), the dumpdir command should be used to define the
directory where the measurement histories are saved.
An example of the command is
dumpdir /var/log/chrony
A source whose IP address is 1.2.3.4 would have its measurement
history saved in the file `/var/log/chrony/1.2.3.4.dat'.
4.2.14 dumponexit
-----------------
If this command is present, it indicates that `chronyd' should save
the measurement history for each of its time sources recorded whenever
the program exits. (See the dumpdir command above).
4.2.15 initstepslew
-------------------
In normal operation, `chronyd' always slews the time when it needs to
adjust the system clock. For example, to correct a system clock which
is 1 second slow, `chronyd' slightly increases the amount by which the
system clock is advanced on each clock interrupt, until the error is
removed. (Actually, this is done by calling the `adjtime()' or similar
system function which does it for us.) Note that at no time does time
run backwards with this method.
On most Unix systems it is not desirable to step the system clock,
because many programs rely on time advancing monotonically forwards.
When the `chronyd' daemon is initially started, it is possible that
the system clock is considerably in error. Attempting to correct such
an error by slewing may not be sensible, since it may take several hours
to correct the error by this means.
The purpose of the `initstepslew' directive is to allow `chronyd' to
make a rapid measurement of the system clock error at boot time, and to
correct the system clock by stepping before normal operation begins.
Since this would normally be performed only at an appropriate point in
the system boot sequence, no other software should be adversely affected
by the step.
If the correction required is less than a specified threshold, a
slew is used instead. This makes it easier to restart `chronyd' whilst
the system is in normal operation.
The `initstepslew' directive takes a threshold and a list of NTP
servers as arguments. A maximum of 8 will be used. Each of the servers
is rapidly polled several times, and a majority voting mechanism used to
find the most likely range of system clock error that is present. A
step (or slew) is applied to the system clock to correct this error.
`chronyd' then enters its normal operating mode (where only slews are
used).
An example of use of the command is
initstepslew 30 foo.bar.com baz.quz.com
where 2 NTP servers are used to make the measurement. The `30'
indicates that if the system's error is found to be 30 seconds or less,
a slew will be used to correct it; if the error is above 30 seconds, a
step will be used.
The `initstepslew' directive can also be used in an isolated LAN
environment, where the clocks are set manually. The most stable
computer is chosen as the master, and the other computers are slaved to
it. If each of the slaves is configured with the local option (see
below), the master can be set up with an `initstepslew' directive which
references some or all of the slaves. Then, if the master machine has
to be rebooted, the slaves can be relied on to 'flywheel' the time for
the master.
4.2.16 keyfile
--------------
This command is used to specify the location of the file containing
ID/key pairs for the following 2 uses:
* Authentication of NTP packets.
* Authentication of administrator commands entered via chronyc.
The format of the command is shown in the example below
keyfile /etc/chrony.keys
The argument is simply the name of the file containing the ID/key
pairs. The format of the file is shown below
10 tulip
11 hyacinth
20 crocus
25 iris
...
Each line consists of an ID and a password. The ID can be any
unsigned integer in the range 0 through 2**32-1. The password can be
any string of characters not containing a space.
For NTP use, the MD5 authentication scheme is always used. This
must be borne in mind if `chronyd' is to inter-operate in authenticated
mode with `xntpd' running on other computers.
The ID for the chronyc authentication key is specified with the
commandkey command (see earlier).
4.2.17 local
------------
The local keyword is used to allow `chronyd' to appear synchronised
to real time (from the viewpoint of clients polling it), even if it has
no current synchronisation source.
This option is normally used on computers in an isolated network,
where several computers are required to synchronise to one other, this
being the "master" which is kept vaguely in line with real time by
manual input.
An example of the command is
local stratum 10
The value 10 may be substituted with other values in the range 1
through 15. Stratum 1 indicates a computer that has a true real-time
reference directly connected to it (e.g. GPS, atomic clock etc) –
such computers are expected to be very close to real time. Stratum 2
computers are those which have a stratum 1 server; stratum 3 computers
have a stratum 2 server and so on.
A large value of 10 indicates that the clock is so many hops away
from a reference clock that its time is fairly unreliable. Put another
way, if the computer ever has access to another computer which is
ultimately synchronised to a reference clock, it will almost certainly
be at a stratum less than 10. Therefore, the choice of a high value
like 10 for the local command prevents the machine's own time from ever
being confused with real time, were it ever to leak out to clients that
have visibility of real servers.
4.2.18 linux_hz
---------------
(This option only applies to Linux).
By default, chronyd will find the value of `HZ' from a kernel header
file at compile time. `HZ' is the nominal number of timer interrupts
per second. If you're running chronyd on the system where it was
built, the value it has should be right, and you don't need to worry
about this option.
This option is provided for people who move a pre-built chronyd onto
a system where the value of HZ in the kernel headers has been changed
from the default value.
An example of the command is
linux_hz 100
4.2.19 linux_freq_scale
-----------------------
(This option only applies to Linux).
By default, chronyd will find the value of `HZ' and `SHIFT_HZ' from
kernel header files at compile time. An internal value called
`freq_scale' is calculated from this. By default it is
(1<<SHIFT_HZ)/HZ, except for the case HZ=100, when special case code is
used which leads to the value 128/128.125. If you're running chronyd
on the system where it was built, the value it has should be right, and
you don't need to worry about this option.
This option is provided for people who move a pre-built chronyd onto
a system where the method by which the kernel computes the reciprocal
of this value has been changed or where the HZ and SHIFT_HZ constants
differ from those on the system where chronyd was built.
An example of the command is
linux_freq_scale 0.99902439
4.2.20 log
----------
The log command indicates that certain information is to be logged.
`measurements'
This option logs the raw NTP measurements and related information
to a file called measurements.log.
`statistics'
This option logs information about the regression processing to a
file called statistics.log.
`tracking'
This option logs changes to the estimate of the system's gain or
loss rate, and any slews made, to a file called tracking.log.
`rtc'
This option logs information about the system's real-time clock.
The files are written to the directory specified by the logdir
command.
An example of the command is
log measurements statistics tracking
4.2.20.1 Measurements log file format
.....................................
An example line (which actually appears as a single line in the file)
from the measurements log file is shown below.
1998-07-22 05:40:50 158.152.1.76 N 8 1111 11 1111 10 10 1 \
-4.966e-03 2.296e-01 1.577e-05 1.615e-01 7.446e-03
The columns are as follows (the quantities in square brackets are the
values from the example line above) :
1. Date [1998-07-22]
2. Hour:Minute:Second [05:40:50]. Note that the date/time pair is
expressed in UTC, not the local time zone.
3. IP address of server/peer from which measurement comes
[158.152.1.76]
4. Leap status (`N' means normal, `-' means that the last minute of
today has 61 seconds, `+' means that the last minute of the day
has 59 seconds, `?' means the remote computer is not currently
synchronised.) [N]
5. Stratum of remote computer. [2]
6. RFC1305 tests 1 through 4 (1=pass, 0=fail) [1111]
7. Tests for maximum delay and maximum delay ratio, against user
defined parameters (1=pass, 0=fail) [11]
8. RFC1305 tests 5 through 8 (1=pass, 0=fail) [1111]
9. Local poll [10]
10. Remote poll [10]
11. `Score' (an internal score within each polling level used to
decide when to increase or decrease the polling level. This is
adjusted based on changes to the variance of the measurements
obtained from the source). [1]
12. The estimated local clock error (`theta' in RFC1305). Positive
indicates that the local clock is slow. [-4.966e-03].
13. The peer delay (`delta' in RFC1305). [2.296e-01]
14. The peer dispersion (`epsilon' in RFC1305). [1.577e-05]
15. The root delay (`Delta' in RFC1305). [1.615e-01]
16. The root dispersion (`E' in RFC1305). [7.446e-03]
A banner is periodically written to the log file to indicate the
meanings of the columns.
4.2.20.2 Statistics log file format
...................................
An example line (which actually appears as a single line in the file)
from the measurements log file is shown below.
1998-07-22 05:40:50 158.152.1.76 6.261e-03 -3.247e-03 \
2.220e-03 1.874e-06 1.080e-06 7.8e-02 16 0 8
The columns are as follows (the quantities in square brackets are the
values from the example line above) :
1. Date [1998-07-22]
2. Hour:Minute:Second [05:40:50]. Note that the date/time pair is
expressed in UTC, not the local time zone.
3. IP address of server/peer from which measurement comes
[158.152.1.76]
4. The estimated standard deviation of the measurements from the
source (in seconds). [6.261e-03]
5. The estimated offset of the source (in seconds, positive means the
local clock is estimated to be fast, in this case). [-3.247e-03]
6. The estimated standard deviation of the offset estimate (in
seconds). [2.220e-03]
7. The estimated rate at which the local clock is gaining or losing
time relative to the source (in seconds per second, positive means
the local clock is gaining). This is relative to the compensation
currently being applied to the local clock, _not_ to the local
clock without any compensation. [1.874e-06]
8. The estimated error in the rate value (in seconds per second).
[1.080e-06].
9. The ration of |old_rate - new_rate| / old_rate_error. Large values
indicate the statistics are not modelling the source very well.
[7.8e-02]
10. The number of measurements currently being used for the regression
algorithm. [16]
11. The new starting index (the oldest sample has index 0; this is the
method used to prune old samples when it no longer looks like the
measurements fit a linear model). [0, i.e. no samples discarded
this time]
12. The number of runs. The number of runs of regression residuals
with the same sign is computed. If this is too small it indicates
that the measurements are no longer represented well by a linear
model and that some older samples need to be discarded. The
number of runs for the data that is being retained is tabulated.
Values of approximately half the number of samples are expected.
[8]
A banner is periodically written to the log file to indicate the
meanings of the columns.
4.2.20.3 Tracking log file format
.................................
An example line (which actually appears as a single line in the file)
from the measurements log file is shown below.
1998-07-22 05:40:50 158.152.1.76 3 340.529 1.606 1.046e-03
The columns are as follows (the quantities in square brackets are the
values from the example line above) :
1. Date [1998-07-22]
2. Hour:Minute:Second [05:40:50]. Note that the date/time pair is
expressed in UTC, not the local time zone.
3. The IP address of the server/peer to which the local system is
synchronised. [158.152.1.76]
4. The stratum of the local system. [3]
5. The local system frequency (in ppm, positive means the local
system runs fast of UTC). [340.529]
6. The error bounds on the frequency (in ppm) [1.606]
7. The estimated local offset at the epoch (which is rapidly
corrected by slewing the local clock. (In seconds, positive
indicates the local system is fast of UTC). [1.046e-3]
A banner is periodically written to the log file to indicate the
meanings of the columns.
4.2.20.4 Real-time clock log file format
........................................
An example line (which actually appears as a single line in the file)
from the measurements log file is shown below.
1998-07-22 05:40:50 -0.037360 1 -0.037434\
-37.948 12 5 120
The columns are as follows (the quantities in square brackets are the
values from the example line above) :
1. Date [1998-07-22]
2. Hour:Minute:Second [05:40:50]. Note that the date/time pair is
expressed in UTC, not the local time zone.
3. The measured offset between the system's real time clock and the
system (`gettimeofday()') time. In seconds, positive indicates
that the RTC is fast of the system time. [-0.037360].
4. Flag indicating whether the regression has produced valid
coefficients. (1 for yes, 0 for no). [1]
5. Offset at the current time predicted by the regression process. A
large difference between this value and the measured offset tends
to indicate that the measurement is an outlier with a serious
measurement error. [-0.037434].
6. The rate at which the RTC is losing or gaining time relative to the
system clock. In ppm, with positive indicating that the RTC is
gaining time. [-37.948]
7. The number of measurements used in the regression. [12]
8. The number of runs of regression residuals of the same sign. Low
values indicate that a straight line is no longer a good model of
the measured data and that older measurements should be discarded.
[5]
9. The measurement interval used prior to the measurement being made
(in seconds). [120]
A banner is periodically written to the log file to indicate the
meanings of the columns.
4.2.21 logchange
----------------
This directive forces `chronyd' to send a message to syslog if it
makes a system clock adjustment larger than a threshold value. An
example of use is
logchange 0.5
which would cause a syslog message to be generated a system clock
error of over 0.5 seconds starts to be compensated.
Clock errors detected either via NTP packets or via timestamps
entered via the `settime' command of `chronyc' are logged.
This directive assumes that syslog messages are appearing where
somebody can see them. This allows that person to see if a large error
has arisen, e.g. because of a fault, or because of faulty timezone
handling, for example when summer time (daylight saving) starts or ends.
4.2.22 logdir
-------------
This directive allows the directory where log files are written to be
specified.
An example of the use of this directive is
logdir /var/log/chrony
4.2.23 mailonchange
-------------------
This directive defines an email address to which mail should be sent
if chronyd applies a correction exceeding a particular threshold to the
system clock.
An example of use of this directive is
mailonchange root@localhost 0.5
This would send a mail message to root if a change of more than 0.5
seconds were applied to the system clock.
4.2.24 manual
-------------
The `manual' directive enables support at run-time for the `settime'
command in chronyc (*note settime command::). If no `manual' directive
is included, any attempt to use the `settime' command in chronyc will
be met with an error message.
Note that the `settime' command can be enabled at run-time using the
`manual' command in chronyc (*note manual command::). (The idea of the
two commands is that the `manual' command controls the manual clock
driver's behaviour, whereas the `settime' command allows samples of
manually entered time to be provided).
4.2.25 maxupdateskew
--------------------
One of `chronyd's' tasks is to work out how fast or slow the
computer's clock runs relative to its reference sources. In addition,
it computes an estimate of the error bounds around the estimated value.
If the range of error is too large, it probably indicates that the
measurements have not settled down yet, and that the estimated gain or
loss rate is not very reliable.
The `maxupdateskew' parameter allows the threshold for determining
whether an estimate may be so unreliable that it should not be used.
The syntax is
maxupdateskew <skew-in-ppm>
Typical values for <skew-in-ppm> might be 100 for a dial-up
connection to servers over a phone line, and 5 or 10 for a computer on
a LAN.
It should be noted that this is not the only means of protection
against using unreliable estimates. At all times, `chronyd' keeps
track of both the estimated gain or loss rate, and the error bound on
the estimate. When a new estimate is generated following another
measurement from one of the sources, a weighted combination algorithm is
used to update the master estimate. So if `chronyd' has an existing
highly-reliable master estimate and a new estimate is generated which
has large error bounds, the existing master estimate will dominate in
the new master estimate.
4.2.26 noclientlog
------------------
This directive, which takes no arguments, specifies that client
accesses are not to be logged. Normally they are logged, allowing
statistics to be reported using the `clients' command in `chronyc'.
4.2.27 peer
-----------
The syntax of this directive is identical to that for the `server'
directive (*note server directive::), except that it is used to specify
an NTP peer rather than an NTP server.
4.2.28 pidfile
--------------
chronyd always writes its process ID (pid) to a file, and checks
this file on startup to see if another chronyd may already be running
on the system. By default, the file used is `/var/run/chronyd.pid'.
The `pidfile' directive allows the name to be changed, e.g.
pidfile /var/tmp/chronyd.pid
4.2.29 port
-----------
This option allows you to configure the port used for the NTP service
on your machine.
The compiled in default is udp/123, the standard NTP port. It is
unlikely that you would ever need to change this value. A possible
exception would be if you wanted to operate strictly in client-only
mode and never be available as a server to xntpd clients.
An example of the port command is
port 11123
This would change the NTP port served by chronyd on the computer to
udp/11123.
4.2.30 rtcdevice
----------------
The `rtcdevice' directive defines the name of the device file for
accessing the real time clock. By default this is `/dev/rtc/', unless
the directive is used to set a different value. This applies to Linux
systems with devfs. An example of use is
rtcdevice /dev/misc/rtc
4.2.31 rtcfile
--------------
The `rtcfile' directive defines the name of the file in which
`chronyd' can save parameters associated with tracking the accuracy of
the system's real-time clock (RTC).
The syntax is illustrated in the following example
rtcfile /etc/chrony.rtc
`chronyd' saves information in this file when it exits and when the
`writertc' command is issued in `chronyc'. The information saved is
the RTC's error at some epoch, that epoch (in seconds since January 1
1970), and the rate at which the RTC gains or loses time.
So far, the support for real-time clocks is limited - their code is
even more system-specific than the rest of the software. You can only
use the real time clock facilities (the `rtcfile' directive and the
`-s' command line option to `chronyd') if the following three
conditions apply:
1. You are running Linux version 2.2.x or 2.4.x (for any value of x),
or v2.0.x with x>=32.
2. You have compiled the kernel with extended real-time clock support
(i.e. the `/dev/rtc' device is capable of doing useful things).
3. You don't have other applications that need to make use of
`/dev/rtc' at all.
4.2.32 rtconutc
---------------
`chronyd' assumes by default that the real time clock (RTC) keeps
local time (including any daylight saving changes). This is convenient
on PCs running Linux which are dual-booted with DOS or Windows.
NOTE : IF YOU KEEP THE REAL TIME CLOCK ON LOCAL TIME AND YOUR
COMPUTER IS OFF WHEN DAYLIGHT SAVING (SUMMER TIME) STARTS OR ENDS, THE
COMPUTER'S SYSTEM TIME WILL BE ONE HOUR IN ERROR WHEN YOU NEXT BOOT AND
START CHRONYD.
An alternative is for the RTC to keep Universal Coordinated Time
(UTC). This does not suffer from the 1 hour problem when daylight
saving starts or ends.
If the `rtconutc' directive appears, it means the RTC is required to
keep UTC. The directive takes no arguments. It is equivalent to
specifying the `-u' switch to the Linux `/sbin/clock' program.
4.2.33 server
-------------
The `server' directive allows NTP servers to be specified. The
client/server relationship is strictly hierarchical : a client may
synchronise its system time to that of the server, but the server's
system time will never be influenced by that of a client.
The `server' directive is immediately followed by either the name of
the server, or its IP address in dotted-quad notation. The server
command also supports a number of subfields (which may be defined in any
order):
`port'
This option allows the UDP port on which the server understands NTP
requests to be specified. For normal servers this option should
not be required (the default is 123, the standard NTP port).
`minpoll'
Although `chronyd' will trim the rate at which it samples the
server during normal operation, the user may wish to constrain the
minimum polling interval. This is always defined as a power of 2,
so <tt/minpoll 5/ would mean that the polling interval cannot drop
below 32 seconds. The default is 6 (64 seconds).
`maxpoll'
In a similar way, the user may wish to constrain the maximum
polling interval. Again this is specified as a power of 2, so
<tt/maxpoll 9/ indicates that the polling interval must stay at or
below 512 seconds. The default is 10 (1024 seconds).
`maxdelay'
`chronyd' uses the network round-trip delay to the server to
determine how accurate a particular measurement is likely to be.
Long round-trip delays indicate that the request, or the response,
or both were delayed. If only one of the messages was delayed the
measurement error is likely to be substantial.
For small variations in round trip delay, `chronyd' uses a
weighting scheme when processing the measurements. However,
beyond a certain level of delay the measurements are likely to be
so corrupted as to be useless. (This is particularly so on
dial-up or other slow links, where a long delay probably indicates
a highly asymmetric delay caused by the response waiting behind a
lot of packets related to a download of some sort).
If the user knows that round trip delays above a certain level
should cause the measurement to be ignored, this level can be
defined with the maxdelay command. For example, <tt/maxdelay 0.3/
would indicate that measurements with a round-trip delay of 0.3
seconds or more should be ignored.
`maxdelayratio'
This option is similar to the maxdelay option above. `chronyd'
keeps a record of the minimum round-trip delay amongst the previous
measurements that it has buffered. If a measurement has a round
trip delay that is greater than the maxdelayratio times the
minimum delay, it will be rejected.
`presend'
If the timing measurements being made by `chronyd' are the only
network data passing between two computers, you may find that some
measurements are badly skewed due to either the client or the
server having to do an ARP lookup on the other party prior to
transmitting a packet. This is more of a problem with long
sampling intervals, which may be similar in duration to the
lifetime of entries in the ARP caches of the machines.
In order to avoid this problem, the `presend' option may be used.
It takes a single integer argument, which is the smallest polling
interval for which a pair of packets will be exchanged between the
client and the server prior to the actual measurement being
initiated by the client. For example, with the following option
included in a `server' directive :
presend 9
when the polling interval is 512 seconds or more, a UDP echo
datagram will be sent to the server a short time (currently 4
seconds) before the NTP client mode datagram.
`key'
The NTP protocol supports the inclusion of checksums in the
packets, to prevent computers having their system time upset by
rogue packets being sent to them. The checksums are generated as
a function of a password, using the MD5 algorithm.
The association between key numbers and passwords is contained in
the keys file, defined by the keyfile command.
If the key option is present, `chronyd' will attempt to use
authenticated packets when communicating with this server. The key
number used will be the single argument to the key option. The
server must have the same password for this key number configured,
otherwise no relationship between the computers will be possible.
`offline'
If the server will not be reachable when `chronyd' is started, the
offline option may be specified. `chronyd' will not try to poll
the server until it is enabled to do so (by using the online
option of `chronyc').
`auto_offline'
If this option is set, the server will be assumed to have gone
offline when 2 requests have been sent to it without receiving a
response. This option avoids the need to run the `offline' (*note
offline command::) command from chrony when disconnecting the
dial-up link. (It will still be necessary to use chronyc's
`online' (*note online command::) command when the link has been
established, to enable measurements to start.)
4.3 Running chronyc
===================
Chronyc is the program that can be used to reconfigure options within
the `chronyd' program whilst it is running. Chronyc can also be used
to generate status reports about the operation of `chronyd'.
4.3.1 Basic use
---------------
The program chronyc is run by entering
chronyc
at the command line. The prompt `chronyc' is displayed whilst
chronyc is expecting input from the user, when it is being run from a
terminal. If chronyc's input or output are redirected from/to a file,
the prompt is now shown.
When you are finished entering commands, the commands `exit' or
`quit' will terminate the program. (Entering <Control-D> will also
terminate the program.)
4.3.2 Command line options
--------------------------
Chronyc supports the following command line options.
`-v'
Displays the version number of chronyc on the terminal, and exists.
`-h <host>'
This option allows the user to specify which host running the
`chronyd' program is to be contacted. This allows for remote
configuration, without having to telnet or rlogin to the other host
first.
The default is to contact `chronyd' running on the same host as
that where chronyc is being run.
`-p <port>'
This option allows the user to specify the UDP port number which
the target `chronyd' is using for its command & monitoring
connections. This defaults to the compiled-in default; there
would rarely be a need to change this.
4.3.3 Security with chronyc
---------------------------
Many of the commands available through chronyc have a fair amount of
power to reconfigure the run-time behaviour of `chronyd'. Consequently,
`chronyc' is quite dangerous for the integrity of the target system's
clock performance. Having access to `chronyd' via chronyc is more or
less equivalent to being able to modify `chronyd's' configuration file
(typically `/etc/chrony.conf') and to restart `chronyd'.
Chronyc also provides a number of monitoring (as opposed to
commanding) commands, which will not affect the behaviour of `chronyd'.
However, you may still want to restrict access to these commands.
In view of this, access to some of the capabilities of chronyc will
usually be tightly controlled. There are two mechanisms supported:
1. The set of hosts from which `chronyd' will accept commands can be
restricted. By default, commands will only be accepted from the
same host that `chronyd' is running on.
2. Any command that actually reconfigures some aspect of `chronyd's'
behaviour requires the user of chronyc to know a password. This
password is specified in `chronyd's' keys file (*note keyfile
directive::) and specified via the commandkey option in its
configuration file (*note commandkey directive::).
Only the following commands can be used _without_ providing a
password:
* `exit'
* `help'
* `password'
* `quit'
* `rtcdata'
* `sources'
* `sourcestats'
* `tracking'
All other commands require a password to have been specified
previously, because they affect `chronyd's' operation.
4.3.4 Command reference
-----------------------
This section describes each of the commands available within the
chronyc program. Chronyc offers the user a simple command-line driven
interface.
4.3.4.1 accheck
...............
This command allows you to check whether client NTP access is allowed
from a particular host.
Examples of use, showing a named host and a numeric IP address, are
as follows:
accheck a.b.c
accheck 1.2.3.4
This command can be used to examine the effect of a series of
`allow', `allow all', `deny' and `deny all' commands specified either
via chronyc, or in `chronyd's' configuration file.
4.3.4.2 activity
................
This command reports the number of servers/peers that are online and
offline. If the auto_offline option is used in specifying some of the
servers/peers, the `activity' command may be useful for detecting when
all of them have entered the offline state after the PPP link has been
disconnected.
The report shows the number of servers/peers in 4 states:
* `online' : the server/peer is currently online (i.e. assumed by
chronyd to be reachable)
* `offline' : the server/peer is currently offline (i.e. assumed by
chronyd to be unreachable, and no measurements from it will be
attempted.)
* `burst_online' : a burst command has been initiated for the
server/peer and is being performed; after the burst is complete,
the server/peer will be returned to the online state.
* `burst_offline' : a burst command has been initiated for the
server/peer and is being performed; after the burst is complete,
the server/peer will be returned to the offline state.
4.3.4.3 add peer
................
The `add peer' command allows a new NTP peer to be added whilst
`chronyd' is running.
Following the words `add peer', the syntax of the following
parameters and options is identical to that for the `peer' directive in
the configuration file (*note peer directive::).
An example of using this command is shown below.
add peer foo.bar.com minpoll 6 maxpoll 10 authkey 25
4.3.4.4 add server
..................
The `add server' command allows a new NTP server to be added whilst
`chronyd' is running.
Following the words `add server', the syntax of the following
parameters and options is identical to that for the `server' directive
in the configuration file (*note server directive::).
An example of using this command is shown below.
add server foo.bar.com minpoll 6 maxpoll 10 authkey 25
4.3.4.5 allow
.............
The effect of the allow command is identical to the `allow'
directive in the configuration file (*note allow directive::).
The syntax is illustrated in the following examples:
allow foo.bar.com
allow 1.2
allow 3.4.5
allow 6.7.8/22
allow 6.7.8.9/22
allow
The effect of each of these examples is the same as that of the
`allow' directive in the configuration file.
4.3.4.6 allow all
.................
The effect of the allow command is identical to the `allow all'
directive in the configuration file (*note allow directive::).
4.3.4.7 burst
.............
The `burst' command tells `chronyd' to make a set of measurements to
each of its sources over a short duration (rather than the usual
periodic measurements that it makes). After such a burst, `chronyd'
will revert to the previous state for each source. This might be either
online, if the source was being periodically measured in the normal way,
or offline, if the source had been indicated as being offline.
(Switching a source between the online and offline states is described
in *Note online command::, *Note offline command::).
The syntax of the burst command is as follows
burst <n-good-measurements>/<max-measurements> [<mask>/<masked-address>]
The mask and masked-address arguments are optional, in which case
`chronyd' will initiate a burst for all of its currently defined
sources.
The arguments have the following meaning and format.
`n-good-measurements'
This defines the number of good measurements that `chronyd' will
want to obtain from each source. A measurement is good if it
passes certain tests, for example, the round trip time to the
source must be acceptable. (This allows `chronyd' to reject
measurements that are likely to be bogus.)
`max-measurements'
This defines the maximum number of measurements that `chronyd' will
attempt to make, even if the required number of good measurements
has not been obtained.
`mask'
This is a dotted quad argument (e.g. `255.255.255.0') with which
the IP address of each of `chronyd''s sources is to be masked.
`masked-address'
This is a dotted quad argument (e.g. `1.2.3.0'). If the masked IP
address of a source matches this value then the burst command is
applied to that source.
If no mask or masked address arguments are provided, the default is
`0.0.0.0' and `0.0.0.0' respectively, which will match every source.
An example of the two-argument form of the command is
burst 2/10
This will cause `chronyd' to attempt to get two good measurements
from each source, stopping after two have been obtained, but in no
event will it try more than ten probes to the source.
An example of the four-argument form of the command is
burst 2/10 255.255.0.0/1.2.0.0
In this case, the two out of ten sampling will only be applied to
sources whose IP addresses are of the form `1.2.x.y', where x and y are
arbitrary.
4.3.4.8 clients
...............
This command shows a list of all clients that have accessed the
server, through either the NTP or command/monitoring ports. There are
no arguments.
An example of the output is
Hostname Client Peer CmdAuth CmdNorm CmdBad LstN LstC
========================= ====== ====== ====== ====== ====== ==== ====
localhost 0 0 15 1 0 29y 0
aardvark.xxx 4 0 0 0 0 49 29y
badger.xxx 4 0 0 0 0 6 29y
Each row shows the data for a single host. Only hosts that have
passed the host access checks (set with the `allow', `deny', `cmdallow'
and `cmddeny' commands or configuration file directives) are logged.
The columns are as follows:
1. The hostname of the client
2. The number of times the client has accessed the server using an NTP
client mode packet.
3. The number of times the client has accessed the server using an NTP
symmetric active mode packet.
4. The number of authenticated command packets that have been
processed from the client (i.e. those following a successful
`password' command).
5. The number of unauthenticated command packets that have been
processed from the client.
6. The number of bad command packets received from the client (not all
forms of bad packet are logged).
7. Time since the last NTP packet was received
8. Time since the last command packet was received
The last two entries will be shown as the time since 1970 if no
packet of that type has ever been received.
4.3.4.9 cmdaccheck
..................
This command is similar to the `accheck' command, except that it is
used to check whether command access is permitted from a named host.
Examples of use are as follows:
cmdaccheck a.b.c
cmdaccheck 1.2.3.4
4.3.4.10 cmdallow
.................
This is similar to the `allow' command, except that it is used to
allow particular hosts or subnets to use the chronyc program to interact
with `chronyd' on the current host.
4.3.4.11 cmdallow all
.....................
This is similar to the `allow all' command, except that it is used
toallow particular hosts or subnets to use the chronyc program to
interactwith `chronyd' on the current host.
4.3.4.12 cmddeny
................
This is similar to the `deny' command, except that it is used to
allow particular hosts or subnets to use the chronyc program to interact
with `chronyd' on the current host.
4.3.4.13 cmddeny all
....................
This is similar to the `deny all' command, except that it is used to
allow particular hosts or subnets to use the chronyc program to
interact with `chronyd' on the current host.
4.3.4.14 cyclelogs
..................
The `cyclelogs' command causes all of `chronyd's' open log files to
be closed and re-opened. This allows them to be renamed so that they
can be periodically purged. An example of how to do this is shown
below.
% mv /var/log/chrony/measurements.log /var/log/chrony/measurements1.log
% chronyc
chronyc> password aardvark
200 OK
chronyc> cyclelogs
200 OK
chronyc> exit
% ls -l /var/log/chrony
-rw-r--r-- 1 root root 0 Jun 8 18:17 measurements.log
-rw-r--r-- 1 root root 12345 Jun 8 18:17 measurements1.log
% rm -f measurements1.log
4.3.4.15 delete
...............
The `delete' command allows an NTP server or peer to be removed from
the current set of sources.
The syntax is illustrated in the examples below.
delete foo.bar.com
delete 1.2.3.4
There is one parameter, the name or IP address of the server or peer
to be deleted.
4.3.4.16 deny
.............
The effect of the allow command is identical to the `deny' directive
in the configuration file (*note deny directive::).
The syntax is illustrated in the following examples:
deny foo.bar.com
deny 1.2
deny 3.4.5
deny 6.7.8/22
deny 6.7.8.9/22
deny
4.3.4.17 deny all
.................
The effect of the allow command is identical to the `deny all'
directive in the configuration file (*note deny directive::).
4.3.4.18 dump
.............
The `dump' command causes `chronyd' to write its current history of
measurements for each of its sources to dump files, either for
inspection or to support the `-r' option when `chronyd' is restarted.
The `dump' command is somewhat equivalent to the `dumponexit'
directive in the chrony configuration file. *Note dumponexit
directive::.
To use the `dump', you probably want to configure the name of the
directory into which the dump files will be written. This can only be
done in the configuration file, see *Note dumpdir directive::.
4.3.4.19 exit
.............
The exit command exits from chronyc and returns the user to the shell
(same as the quit command).
4.3.4.20 help
.............
The help command displays a summary of the commands and their
arguments.
4.3.4.21 local
..............
The `local' command allows `chronyd' to be told that it is to appear
as a reference source, even if it is not itself properly synchronised to
an external source. (This can be used on isolated networks, to allow
one computer to be a master time server with the other computers slaving
to it.) The `local' command is somewhat equivalent to the `local'
directive in the configuration file, see *Note local directive::.
The syntax is as shown in the following examples.
local stratum 10
local off
The first example enables the local reference mode on the host, and
sets the stratum at which it should claim to be synchronised.
The second example disables the local reference mode.
4.3.4.22 makestep
.................
Normally chronyd will cause the system to gradually correct any time
offset, by slowing down or speeding up the clock as required. In
certain situations, the system clock may be so far adrift that this
slewing process would take a very long time to correct the system clock.
The `makestep' command can be used in this situation. It cancels
any remaining correction that was being slewed, and jumps the system
clock by the equivalent amount, making it correct immediately.
BE WARNED - certain software will be seriously affected by such
jumps to the system time. (That is the reason why chronyd uses slewing
normally.)
The `makestep' command is currently only available on the Linux
version of chrony.
4.3.4.23 manual
...............
The manual command enables and disables use of the `settime' command
(*note settime command::), and is used to modify the behaviour of the
manual clock driver.
Examples of the command are shown below.
manual on
manual off
manual delete 1
manual list
manual reset
The `on' form of the command enables use of the `settime' command.
The `off' form of the command disables use of the `settime' command.
The `list' form of the command lists all the samples currently
stored in `chronyd'. The output is illustrated below.
210 n_samples = 1
# Date Time(UTC) Slewed Original Residual
====================================================
0 27Jan99 22:09:20 0.00 0.97 0.00
The columns as as follows :
1. The sample index (used for the `manual delete' command)
2. The date and time of the sample
3. The system clock error when the timestamp was entered, adjusted to
allow for changes made to the system clock since.
4. The system clock error when the timestamp was entered, as it
originally was (without allowing for changes to the system clock
since).
5. The regression residual at this point, in seconds. This allows
'outliers' to be easily spotted, so that they can be deleted using
the `manual delete' command.
The `delete' form of the command deletes a single sample. The
parameter is the index of the sample, as shown in the first column of
the output from `manual list'. Following deletion of the data point,
the current error and drift rate are re-estimated from the remaining
data points and the system clock trimmed if necessary. This option is
intended to allow 'outliers' to be discarded, i.e. samples where the
administrator realises he/she has entered a very poor timestamp.
The `reset' form of the command deletes all samples at once. The
system clock is left running as it was before the command was entered.
4.3.4.24 maxdelay
.................
This allows the `maxdelay' option for one of the sources to be
modified, in the same way as specifying the `maxdelay' option for the
`server' directive in the configuration file (*note server directive::).
The following examples illustrate the syntax
maxdelay foo.bar.com 0.3
maxdelay 1.2.3.4 0.0015
The first example sets the maximum network delay allowed for a
measurement to the host `foo.bar.com' to 0.3 seconds. The second
example sets the maximum network delay for a measurement to the host
with IP address `1.2.3.4' to 1.5 milliseconds.
(Any measurement whose network delay exceeds the specified value is
discarded.)
4.3.4.25 maxdelayratio
......................
This allows the `maxdelayratio' option for one of the sources to be
modified, in the same way as specifying the `maxdelayratio' option for
the `server' directive in the configuration file (*note server
directive::).
The following examples illustrate the syntax
maxdelayratio foo.bar.com 1.5
maxdelayratio 1.2.3.4 2.0
The first example sets the maximum network delay for a measurement to
the host `foo.bar.com' to be 1.5 times the minimum delay found amongst
the previous measurements that have been retained. The second example
sets the maximum network delay for a measurement to the host with IP
address `1.2.3.4' to be double the retained minimum.
As for `maxdelay', any measurement whose network delay is too large
will be discarded.
4.3.4.26 maxpoll
................
The `maxpoll' command is used to modify the minimum polling interval
for one of the current set of sources. It is equivalent to the
`maxpoll' option in the `server' directive in the configuration file
(*note server directive::).
The syntax is as follows
maxpoll <host> <new-maxpoll>
where the host can be specified as either a machine name or
dotted-quad IP address. The new minimum poll is specified as a base-2
logarithm of the number of seconds between polls (e.g. specify 6 for 64
second sampling).
An example is
maxpoll foo.bar.com 10
which sets the maximum polling interval for the host `foo.bar.com'
to 1024 seconds.
Note that the new maximum polling interval only takes effect after
the next measurement has been made.
4.3.4.27 maxupdateskew
......................
This command has the same effect as the `maxupdateskew' directive in
the configuration file, see *Note maxupdateskew directive::.
4.3.4.28 minpoll
................
The `minpoll' command is used to modify the minimum polling interval
for one of the current set of sources. It is equivalent to the
`minpoll' option in the `server' directive in the configuration file
(*note server directive::).
The syntax is as follows
minpoll <host> <new-minpoll>
where the host can be specified as either a machine name or
dotted-quad IP address. The new minimum poll is specified as a base-2
logarithm of the number of seconds between polls (e.g. specify 6 for 64
second sampling).
An example is
minpoll foo.bar.com 5
which sets the minimum polling interval for the host `foo.bar.com'
to 32 seconds.
Note that the new minimum polling interval only takes effect after
the next measurement has been made.
4.3.4.29 offline
................
The `offline' command is used to warn `chronyd' that the network
connection to a particular host or hosts is about to be lost. It should
be used on computers with a dial-up or similar connection to their time
sources, to warn `chronyd' that the connection is about to be broken.
An example of how to use `offline' in this case is shown in *Note
Advising chronyd of internet availability::.
Another case where `offline' could be used is where a computer
serves time to a local group of computers, and has a permanant
connection to true time servers outside the organisation. However, the
external connection is heavily loaded at certain times of the day and
the measurements obtained are less reliable at those times. In this
case, it is probably most useful to determine the gain/loss rate during
the quiet periods and let the whole network coast through the loaded
periods. The `offline' and `online' commands can be used to achieve
this. The situation is shown in the figure below.
+----------+
|Ext source|
+----------+
|
|
|/| <-- Link with variable
| reliability
|
+-------------------+
|Local master server|
+-------------------+
|
+---+---+-----+-----+----+----+
| | | | | | |
Local clients
If the source to which `chronyd' is currently synchronised is
indicated offline in this way, `chronyd' will continue to treat it as
the synchronisation source. If the network connection were broken
without the `offline' command being used, `chronyd' would assume that
the source had failed and would attempt to pick another synchronisation
source.
There are two forms of the `offline' command. The first form is a
wildcard, meaning all sources. The second form allows a IP address mask
and a masked address to be specified. These forms are illustrated
below.
offline
offline 255.255.255.0/1.2.3.0
The second form means that the `offline' command is to be applied to
any source whose IP address is in the 1.2.3 subnet. (The host's
address is logically and-ed with the mask, and if the result matches the
masked-address the host is processed).
The wildcard form of the address is actually equivalent to
offline 0.0.0.0/0.0.0.0
4.3.4.30 online
...............
The `online' command is opposite in function to the `offline'
command. It is used to advise `chronyd' that network connectivity to a
particular source or sources has been restored.
The syntax is identical to that of the `offline' command, see *Note
offline command::.
4.3.4.31 password
.................
The password command is used to allow chronyc to send privileged
commands to `chronyd'. The password can either be entered on the
command line, or can be entered without echoing. The syntax for
entering the password on the command line is as follows
password xyzzy
To enter the password without it being echoed, enter
password
The computer will respond with a `Password:' prompt, at which you
should enter the password and press return. (Note that the no-echo mode
is limited to 8 characters on SunOS 4.1 due to limitations in the system
library. Other systems do not have this restriction.)
The password is any string of characters not containing whitespace.
It has to match `chronyd's' currently defined command key (*note
commandkey directive::).
4.3.4.32 quit
.............
The quit command exits from chronyc and returns the user to the shell
(same as the exit command).
4.3.4.33 rtcdata
................
The `rtcdata' command displays the current real time clock RTC
parameters.
An example output is shown below.
RTC ref time (GMT) : Sat May 30 07:25:56 1998
Number of samples : 10
Number of runs : 5
Sample span period : 549
RTC is fast by : -1.632736 seconds
RTC gains time at : -107.623 ppm
The fields have the following meaning
`RTC ref time (GMT)'
This is the RTC reading the last time its error was measured.
`Number of samples'
This is the number of previous measurements being used to
determine the RTC gain/loss rate.
`Number of runs'
This is the number of runs of residuals of the same sign following
the regression fit for (RTC error) versus (RTC time). A value
which is small indicates that the measurements are not well
approximated by a linear model, and that the algorithm will tend
to delete the older measurements to improve the fit.
`Sample span period'
This is the period that the measurements span (from the oldest to
the newest). Without a unit the value is in seconds; suffixes `m'
for minutes, `h' for hours, `d' for days or `y' for years may be
used.
`RTC is fast by'
This is the estimate of how many seconds fast the RTC when it
thought the time was at the reference time (above). If this value
is large, you may (or may not) want to use the `trimrtc' command
to bring the RTC into line with the system clock. (Note, a large
error will not affect `chronyd's' operation, unless it becomes so
big as to start causing rounding errors.
`RTC gains time at'
This is the amount of time gained (positive) or lost (negative) by
the real time clock for each second that it ticks. It is measured
in parts per million. So if the value shown was +1, suppose the
RTC was exactly right when it crosses a particular second
boundary. Then it would be 1 microsecond fast when it crosses its
next second boundary.
4.3.4.34 settime
................
The `settime' command allows the current time to be entered
manually, if this option has been configured into `chronyd'. (It may be
configured either with the `manual' directive in the configuration file
(*note manual directive::), or with the `manual' command of chronyc
(*note manual command::).
It should be noted that the computer's sense of time will only be as
accurate as the reference you use for providing this input (e.g. your
watch), as well as how well you can time the press of the return key.
When inputting time to an isolated network, I have a battery operated
alarm clock that is synchronised to the Rugby MSF time signal in the UK.
Providing your computer's time zone is set up properly, you will be
able to enter a local time (rather than UTC).
The response to a successful `settime' command indicates the amount
that the computer's clock was wrong. It should be apparent from this if
you have entered the time wrongly, e.g. with the wrong time zone.
The rate of drift of the system clock is estimated by a regression
process using the entered measurement and all previous measurements
entered during the present run of `chronyd'. However, the entered
measurement is used for adjusting the current clock offset (rather than
the estimated intercept from the regression, which is ignored).
Contrast what happens with the `manual delete' command, where the
intercept is used to set the current offset (since there is no
measurement that has just been typed in in that case).
The time is parsed by the public domain `getdate' algorithm.
Consequently, you can only specify time to the nearest second.
Examples of inputs that are valid are shown below.
settime 16:30
settime 16:30:05
settime Nov 21, 1997 16:30:05
For a full description of `getdate', get hold of the getdate
documentation (bundled, for example, with the source for GNU tar).
4.3.4.35 sources
................
This command displays information about the current time sources that
`chronyd' is accessing.
The optional argument `-v' can be specified, meaning _verbose_. In
this case, extra caption lines are shown as a reminder of the meanings
of the columns.
210 Number of sources = 3
MS Name/IP address Stratum Poll LastRx Last sample
=======================================================================
^+ a.b.c 3 6 47m -9491us[-6983us] +/- 159ms
^+ d.e.f 3 6 47m +32ms[ +35ms] +/- 274ms
^* g.h.i 2 6 47m +8839us[ +11ms] +/- 214ms
The columns are as follows:
`M'
This indicates the mode of the source. `^' means a server, `='
means a peer and `#' indicates a locally connected reference
clock(1).
`S'
This column indicates the state of the sources. `*' indicates the
source to which `chronyd' is current synchronised. `+' indicates
other acceptable sources. `?' indicates sources to which
connectivity has been lost. `x' indicates a clock which `chronyd'
thinks is is a falseticker (i.e. its time is inconsistent with a
majority of other sources). `~' indicates a source whose time
appears to have too much variability. The `~' condition is also
shown at start-up, until at least 3 samples have been gathered
from it.
`Name/IP address'
This shows the name or the IP address of the source.
`Stratum'
This shows the stratum of the source, as reported in its most
recently received sample. Stratum 1 indicates a computer with a
locally attached reference clock. A computer that is synchronised
to a stratum 1 computer is at stratum 2. A computer that is
synchronised to a stratum 2 computer is at stratum 3, and so on.
`Poll'
This shows the rate at which the source is being polled, as a
base-2 logarithm of the interval in seconds. Thus, a value of 6
would indicate that a measurement is being made every 64 seconds.
`chronyd' automatically varies the polling rate in response to
prevailing conditions.
`LastRx'
This column shows how long ago the last sample was received from
the source. This is normally in seconds. The letters `m', `h',
`d' or `y' indicate minutes, hours, days or years.
`Last sample'
This column shows the offset between the local clock and the
source at the last measurement. The number in the square brackets
shows the actual measured offset. This may be suffixed by `us'
(indicating microseconds), `ms' (indicating milliseconds), or `s'
(indicating seconds). The number to the left of the square
brackets shows the original measurement, adjusted to allow for any
slews applied to the local clock since. The number following the
`+/-' indicator shows the margin of error in the measurement.
Positive offsets indicate that the local clock is fast of the
source.
---------- Footnotes ----------
(1) In the current version this will never be shown, because
`chronyd' has no support for reference clocks yet.
4.3.4.36 sourcestats
....................
The `sourcestats' command displays information about the drift rate
and offset estimatation process for each of the sources currently being
examined by `chronyd'.
The optional argument `-v' can be specified, meaning _verbose_. In
this case, extra caption lines are shown as a reminder of the meanings
of the columns.
An example report is
210 Number of sources = 1
Name/IP Address NP NR Span Frequency Freq Skew Std Dev
========================================================================
abc.def.ghi 11 5 46m -0.001 0.045 25us
The columns are as follows
`Name/IP Address'
This is the name or dotted-quad IP address of the NTP server (or
peer) to which the rest of the line relates.
`NP'
This is the number of sample points currently being retained for
the server. The drift rate and current offset are estimated by
performing a linear regression through these points.
`NR'
This is the number of runs of residuals having the same sign
following the last regression. If this number starts to become
too small relative to the number of samples, it indicates that a
straight line is no longer a good fit to the data. If the number
of runs is too low, `chronyd' discards older samples and re-runs
the regression until the number of runs becomes acceptable.
`Span'
This is the interval between the oldest and newest samples. If no
unit is shown the value is in seconds. In the example, the
interval is 46 minutes.
`Frequency'
This is the estimated residual frequency for the server, in parts
per million. In this case, the computer's clock is estimated to
be running 1 part in 10**9 slow relative to the server.
`Freq Skew'
This is the estimated error bounds on `Freq' (again in parts per
million).
`Std Dev'
This is the estimated sample standard deviation.
4.3.4.37 tracking
.................
The `tracking' command displays parameters about the system's clock
performance. An example of the output is shown below.
Reference ID : 1.2.3.4 (a.b.c)
Stratum : 3
Ref time (UTC) : Sun May 17 06:13:11 1998
System time : 0.000000 seconds fast of NTP time
Frequency : 331.898 ppm fast
Residual freq : 0.004 ppm
Skew : 0.154 ppm
Root delay : 0.373169 seconds
Root dispersion : 0.024780 seconds
The fields are explained as follows.
`Reference ID'
This is the IP address, and name if available, of the server to
which the computer is currently synchronised. If this is
`127.127.1.1' it means the computer is not synchronised to any
external source and that you have the `local' mode operating (via
the `local' command in `chronyc' (*note local command::), or the
`local' directive in the `/etc/chrony.conf' file (*note local
directive::)).
`Stratum'
The stratum indicates how many hops away from a computer with an
attached reference clock we are. Such a computer is a stratum-1
computer, so the computer in the example is two hops away (i.e.
`a.b.c' is a stratum-2 and is synchronised from a stratum-1).
`Ref time'
This is the time (GMT) at which the last measurement from the
reference source was processed.
`System time'
In normal operation, `chronyd' _never_ steps the system clock,
because any jump in the timescale can have adverse consequences for
certain application programs. Instead, any error in the system
clock is corrected by slightly speeding up or slowing down the
system clock until the error has been removed, and then returning
to the system clock's normal speed. A consequence of this is that
there will be a period when the system clock (as read by other
programs using the `gettimeofday()' system call, or by the `date'
command in the shell) will be different from `chronyd's' estimate
of the current true time (which it reports to NTP clients when it
is operating in server mode). The value reported on this line is
the difference due to this effect.
On systems such as Solaris and SunOS, `chronyd' has no means to
adjust the fundamental rate of the system clock, so keeps the
system time correct by periodically making offsets to it as though
an error had been measured. The build up of these offsets will be
observed in this report. On systems such as Linux where `chronyd'
can adjust the fundamental rate of the system clock, this value
will show zero unless a very recent measurement has shown the
system to be error.
`Frequency'
The `frequency' is the rate by which the system's clock would be
would be wrong if `chronyd' was not correcting it. It is
expressed in ppm (parts per million). For example, a value of
1ppm would mean that when the system's clock thinks it has
advanced 1 second, it has actually advanced by 1.000001 seconds
relative to true time.
As you can see in the example, the clock in the computer I
developed `chrony' on is not a very good one - it gains about 30
seconds per day! This was the reason I started to write `chrony'
in the first place.
`Residual freq'
This shows the `residual frequency' for the currently selected
reference source. This reflects any difference between what the
measurements from the reference source indicate the frequency
should be and the frequency currently being used.
The reason this is not always zero is that a smoothing procedure is
applied to the frequency. Each time a measurement from the
reference source is obtained and a new residual frequency
computed, the estimated accuracy of this residual is compared with
the estimated accuracy (see `skew' next) of the existing frequency
value. A weighted average is computed for the new frequency, with
weights depending on these accuracies. If the measurements from
the reference source follow a consistent trend, the residual will
be driven to zero over time.
`Skew'
This is the estimated error bound on the the frequency.
`Root delay'
This is the total of the network path delays to the stratum-1
computer from which the computer is ultimately synchronised.
In certain extreme situations, this value can be negative. (This
can arise in a symmetric peer arrangement where the computers'
frequencies are not tracking each other and the network delay is
very short relative to the turn-around time at each computer.)
`Root dispersion'
This is the total dispersion accumulated through all the computers
back to the stratum-1 computer from which the computer is
ultimately synchronised. Dispersion is due to system clock
resolution, statistical measurement variations etc.
An absolute bound on the computer's clock accuracy (assuming the
stratum-1 computer is correct) is given by
clock_error <= root_dispersion + (0.5 * |root_delay|)
4.3.4.38 trimrtc
................
The `trimrtc' command is used to correct the system's real time
clock (RTC) to the main system clock. It has no effect if the error
between the two clocks is currently estimated at less than a second (the
resolution of the RTC is only 1 second).
The command takes no arguments. It performs the following steps (if
the RTC is more than 1 second away from the system clock):
1. Remember the currently estimated gain/loss rate of the RTC and
flush the previous measurements.
2. Step the real time clock to bring it within a second of the system
clock.
3. Make several measurements to accurately determine the new offset
between the RTC and the system clock (i.e. the remaining fraction
of a second error)
4. Save the RTC parameters to the RTC file (specified with the
`rtcfile' directive in the configuration file (*note rtcfile
directive::).
The last step is done as a precaution against the computer suffering
a power failure before either the daemon exits or the `writertc'
command is issued.
`chronyd' will still work perfectly well both whilst operating and
across machine reboots even if the `trimrtc' command is never used (and
the RTC is allowed to drift away from true time). The `trimrtc'
command is provided as a method by which it can be corrected, in a
manner compatible with `chronyd' using it to maintain accurate time
across machine reboots.
4.3.4.39 writertc
.................
The `writertc' command writes the currently estimated error and
gain/loss rate parameters for the RTC to the RTC file (specified with
the `rtcfile' directive (*note rtcfile directive::)). This information
is also written automatically when `chronyd' is killed (with SIGHUP,
SIGINT, SIGQUIT or SIGTERM).
Appendix A Porting guide
************************
This appendix discusses issues that have arisen in writing the
system-specific parts of the existing ports. This will provide useful
information for those attempting to write ports to other systems.
A.1 System driver files
=======================
The system specific parts of the software are contained in files with
names like `sys_linux.c'.
The following functions are required in a system driver file:
1. A function to read the current frequency
2. A function to set the current frequency
3. A function to slew the system time by a specified delta
4. A function to step the system time by a specified delta
5. A function to work out the error at a particular time between the
system's clock and `chronyd's' estimate of real time. (This is
required because some systems have to track real time by making
the system time follow it in a 'sawtooth' fashion).
The "frequency" is the rate at which the system gains or loses time,
measured relative to the system when running uncompensated.
A.2 Quirks of particular systems
================================
These sections describe quirks in each system type that needed to be
investigated to port the software to each system type.
A.2.1 Linux
-----------
The following quirks have been found in developing the Linux port.
1. In order to avoid floating point arithmetic, the kernel uses
shifting and adding to approximate a scaling of 100/128. This
approximation implies that the frequency set via the `adjtimex()'
system call is not the frequency that is actually obtained. The
method of approximation varies between kernel versions and must be
determined by examining the kernel source. An inverse factor must
be included in the driver to compensate.
2. In some kernel versions, an `adjtimex()' system call with the flags
bits all zeroed will return the amount of offset still to be
corrected. In others (e.g. the 2.0 series beyond 2.0.32), the
offset must be changed in order to get the old offset returned
(similar to `adjtime()' on other systems).
A.2.2 Solaris 2.5
-----------------
The following quirks have been found in developing the Solaris port.
1. The `adjtime()' system call with a zero argument does not cancel an
adjustment that is in progress - it just reports the remaining
adjustment.
2. The `settimeofday()' system call only observes the seconds part of
the argument - any fractional seconds part is lost. second.
3. The kernel variable `dosynctodr' has to be set to zero, otherwise
the system clock is periodically reset to the real-time clock.
A.2.3 SunOS 4.1.4
-----------------
The following quirks have been found in developing the SunOS port.
1. The `adjtime()' system call truncates its argument to a multiple of
the system's `tickadj' variable. (`chronyd' sets that to 100,
giving a 1 part in 100 slewing capability for correcting offsets.)
2. The kernel variable `dosynctodr' has to be set to zero, otherwise
the system clock is periodically reset to the real-time clock.
Appendix B GNU General Public License
*************************************
GNU GENERAL PUBLIC LICENSE
Version 2, June 1991
Copyright (C) 1989, 1991 Free Software Foundation, Inc. 59 Temple
Place - Suite 330, Boston, MA 02111-1307, USA Everyone is permitted to
copy and distribute verbatim copies of this license document, but
changing it is not allowed.
Preamble
The licenses for most software are designed to take away your
freedom to share and change it. By contrast, the GNU General Public
License is intended to guarantee your freedom to share and change free
software-to make sure the software is free for all its users. This
General Public License applies to most of the Free Software
Foundation's software and to any other program whose authors commit to
using it. (Some other Free Software Foundation software is covered by
the GNU Library General Public License instead.) You can apply it to
your programs, too.
When we speak of free software, we are referring to freedom, not
price. Our General Public Licenses are designed to make sure that you
have the freedom to distribute copies of free software (and charge for
this service if you wish), that you receive source code or can get it
if you want it, that you can change the software or use pieces of it in
new free programs; and that you know you can do these things.
To protect your rights, we need to make restrictions that forbid
anyone to deny you these rights or to ask you to surrender the rights.
These restrictions translate to certain responsibilities for you if you
distribute copies of the software, or if you modify it.
For example, if you distribute copies of such a program, whether
gratis or for a fee, you must give the recipients all the rights that
you have. You must make sure that they, too, receive or can get the
source code. And you must show them these terms so they know their
rights.
We protect your rights with two steps: (1) copyright the software,
and (2) offer you this license which gives you legal permission to copy,
distribute and/or modify the software.
Also, for each author's protection and ours, we want to make certain
that everyone understands that there is no warranty for this free
software. If the software is modified by someone else and passed on, we
want its recipients to know that what they have is not the original, so
that any problems introduced by others will not reflect on the original
authors' reputations.
Finally, any free program is threatened constantly by software
patents. We wish to avoid the danger that redistributors of a free
program will individually obtain patent licenses, in effect making the
program proprietary. To prevent this, we have made it clear that any
patent must be licensed for everyone's free use or not licensed at all.
The precise terms and conditions for copying, distribution and
modification follow.
GNU GENERAL PUBLIC LICENSE TERMS AND CONDITIONS FOR COPYING,
DISTRIBUTION AND MODIFICATION
0. This License applies to any program or other work which contains
a notice placed by the copyright holder saying it may be distributed
under the terms of this General Public License. The "Program", below,
refers to any such program or work, and a "work based on the Program"
means either the Program or any derivative work under copyright law:
that is to say, a work containing the Program or a portion of it,
either verbatim or with modifications and/or translated into another
language. (Hereinafter, translation is included without limitation in
the term "modification".) Each licensee is addressed as "you".
Activities other than copying, distribution and modification are not
covered by this License; they are outside its scope. The act of
running the Program is not restricted, and the output from the Program
is covered only if its contents constitute a work based on the Program
(independent of having been made by running the Program). Whether that
is true depends on what the Program does.
1. You may copy and distribute verbatim copies of the Program's
source code as you receive it, in any medium, provided that you
conspicuously and appropriately publish on each copy an appropriate
copyright notice and disclaimer of warranty; keep intact all the
notices that refer to this License and to the absence of any warranty;
and give any other recipients of the Program a copy of this License
along with the Program.
You may charge a fee for the physical act of transferring a copy, and
you may at your option offer warranty protection in exchange for a fee.
2. You may modify your copy or copies of the Program or any portion
of it, thus forming a work based on the Program, and copy and
distribute such modifications or work under the terms of Section 1
above, provided that you also meet all of these conditions:
a) You must cause the modified files to carry prominent notices
stating that you changed the files and the date of any change.
b) You must cause any work that you distribute or publish, that in
whole or in part contains or is derived from the Program or any
part thereof, to be licensed as a whole at no charge to all third
parties under the terms of this License.
c) If the modified program normally reads commands interactively
when run, you must cause it, when started running for such
interactive use in the most ordinary way, to print or display an
announcement including an appropriate copyright notice and a notice
that there is no warranty (or else, saying that you provide a
warranty) and that users may redistribute the program under these
conditions, and telling the user how to view a copy of this
License. (Exception: if the Program itself is interactive but does
not normally print such an announcement, your work based on the
Program is not required to print an announcement.)
These requirements apply to the modified work as a whole. If
identifiable sections of that work are not derived from the Program,
and can be reasonably considered independent and separate works in
themselves, then this License, and its terms, do not apply to those
sections when you distribute them as separate works. But when you
distribute the same sections as part of a whole which is a work based
on the Program, the distribution of the whole must be on the terms of
this License, whose permissions for other licensees extend to the
entire whole, and thus to each and every part regardless of who wrote
it.
Thus, it is not the intent of this section to claim rights or contest
your rights to work written entirely by you; rather, the intent is to
exercise the right to control the distribution of derivative or
collective works based on the Program.
In addition, mere aggregation of another work not based on the
Program with the Program (or with a work based on the Program) on a
volume of a storage or distribution medium does not bring the other
work under the scope of this License.
3. You may copy and distribute the Program (or a work based on it,
under Section 2) in object code or executable form under the terms of
Sections 1 and 2 above provided that you also do one of the following:
a) Accompany it with the complete corresponding machine-readable
source code, which must be distributed under the terms of Sections
1 and 2 above on a medium customarily used for software interchange; or,
b) Accompany it with a written offer, valid for at least three
years, to give any third party, for a charge no more than your cost
of physically performing source distribution, a complete
machine-readable copy of the corresponding source code, to be
distributed under the terms of Sections 1 and 2 above on a medium
customarily used for software interchange; or,
c) Accompany it with the information you received as to the offer
to distribute corresponding source code. (This alternative is
allowed only for noncommercial distribution and only if you
received the program in object code or executable form with such an
offer, in accord with Subsection b above.)
The source code for a work means the preferred form of the work for
making modifications to it. For an executable work, complete source
code means all the source code for all modules it contains, plus any
associated interface definition files, plus the scripts used to control
compilation and installation of the executable. However, as a special
exception, the source code distributed need not include anything that
is normally distributed (in either source or binary form) with the
major components (compiler, kernel, and so on) of the operating system
on which the executable runs, unless that component itself accompanies
the executable.
If distribution of executable or object code is made by offering
access to copy from a designated place, then offering equivalent access
to copy the source code from the same place counts as distribution of
the source code, even though third parties are not compelled to copy
the source along with the object code.
4. You may not copy, modify, sublicense, or distribute the Program
except as expressly provided under this License. Any attempt otherwise
to copy, modify, sublicense or distribute the Program is void, and will
automatically terminate your rights under this License. However,
parties who have received copies, or rights, from you under this
License will not have their licenses terminated so long as such parties
remain in full compliance.
5. You are not required to accept this License, since you have not
signed it. However, nothing else grants you permission to modify or
distribute the Program or its derivative works. These actions are
prohibited by law if you do not accept this License. Therefore, by
modifying or distributing the Program (or any work based on the
Program), you indicate your acceptance of this License to do so, and
all its terms and conditions for copying, distributing or modifying the
Program or works based on it.
6. Each time you redistribute the Program (or any work based on the
Program), the recipient automatically receives a license from the
original licensor to copy, distribute or modify the Program subject to
these terms and conditions. You may not impose any further
restrictions on the recipients' exercise of the rights granted herein.
You are not responsible for enforcing compliance by third parties to
this License.
7. If, as a consequence of a court judgment or allegation of patent
infringement or for any other reason (not limited to patent issues),
conditions are imposed on you (whether by court order, agreement or
otherwise) that contradict the conditions of this License, they do not
excuse you from the conditions of this License. If you cannot
distribute so as to satisfy simultaneously your obligations under this
License and any other pertinent obligations, then as a consequence you
may not distribute the Program at all. For example, if a patent
license would not permit royalty-free redistribution of the Program by
all those who receive copies directly or indirectly through you, then
the only way you could satisfy both it and this License would be to
refrain entirely from distribution of the Program.
If any portion of this section is held invalid or unenforceable under
any particular circumstance, the balance of the section is intended to
apply and the section as a whole is intended to apply in other
circumstances.
It is not the purpose of this section to induce you to infringe any
patents or other property right claims or to contest validity of any
such claims; this section has the sole purpose of protecting the
integrity of the free software distribution system, which is
implemented by public license practices. Many people have made
generous contributions to the wide range of software distributed
through that system in reliance on consistent application of that
system; it is up to the author/donor to decide if he or she is willing
to distribute software through any other system and a licensee cannot
impose that choice.
This section is intended to make thoroughly clear what is believed to
be a consequence of the rest of this License.
8. If the distribution and/or use of the Program is restricted in
certain countries either by patents or by copyrighted interfaces, the
original copyright holder who places the Program under this License may
add an explicit geographical distribution limitation excluding those
countries, so that distribution is permitted only in or among countries
not thus excluded. In such case, this License incorporates the
limitation as if written in the body of this License.
9. The Free Software Foundation may publish revised and/or new
versions of the General Public License from time to time. Such new
versions will be similar in spirit to the present version, but may
differ in detail to address new problems or concerns.
Each version is given a distinguishing version number. If the
Program specifies a version number of this License which applies to it
and "any later version", you have the option of following the terms and
conditions either of that version or of any later version published by
the Free Software Foundation. If the Program does not specify a
version number of this License, you may choose any version ever
published by the Free Software Foundation.
10. If you wish to incorporate parts of the Program into other free
programs whose distribution conditions are different, write to the
author to ask for permission. For software which is copyrighted by the
Free Software Foundation, write to the Free Software Foundation; we
sometimes make exceptions for this. Our decision will be guided by the
two goals of preserving the free status of all derivatives of our free
software and of promoting the sharing and reuse of software generally.
NO WARRANTY
11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO
WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW.
EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR
OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND,
EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS
WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN
WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY
AND/OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU
FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR
CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE
PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING
RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A
FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF
SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
DAMAGES.
END OF TERMS AND CONDITIONS
Appendix: How to Apply These Terms to Your New Programs
If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these
terms.
To do so, attach the following notices to the program. It is safest
to attach them to the start of each source file to most effectively
convey the exclusion of warranty; and each file should have at least
the "copyright" line and a pointer to where the full notice is found.
<one line to give the program's name and a brief idea of what it
does.> Copyright (C) 19yy <name of author>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
USA
Also add information on how to contact you by electronic and paper
mail.
If the program is interactive, make it output a short notice like
this when it starts in an interactive mode:
Gnomovision version 69, Copyright (C) 19yy name of author
Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show
w'. This is free software, and you are welcome to redistribute it
under certain conditions; type `show c' for details.
The hypothetical commands `show w' and `show c' should show the
appropriate parts of the General Public License. Of course, the
commands you use may be called something other than `show w' and `show
c'; they could even be mouse-clicks or menu items-whatever suits your
program.
You should also get your employer (if you work as a programmer) or
your school, if any, to sign a "copyright disclaimer" for the program,
if necessary. Here is a sample; alter the names:
Yoyodyne, Inc., hereby disclaims all copyright interest in the
program `Gnomovision' (which makes passes at compilers) written by
James Hacker.
<signature of Ty Coon>, 1 April 1989 Ty Coon, President of Vice
This General Public License does not permit incorporating your
program into proprietary programs. If your program is a subroutine
library, you may consider it more useful to permit linking proprietary
applications with the library. If this is what you want to do, use the
GNU Library General Public License instead of this License. Table of Contents
*****************
1 Introduction
1.1 Overview
1.2 Acknowledgements
1.3 Availability
1.3.1 Getting the software
1.3.2 Platforms
1.4 Relationship to other software packages
1.4.1 xntpd
1.4.2 timed
1.5 Distribution rights and (lack of) warranty
1.6 Bug reporting and suggestions
1.7 Contributions
2 Installation
2.1 Support for the readline library
2.2 Extra options for package builders
3 Typical operating scenarios
3.1 Computers connected to the internet
3.2 Infrequent connection to true NTP servers
3.2.1 Setting up the configuration file for infrequent connections
3.2.2 How to tell chronyd when the internet link is available.
3.3 Isolated networks
3.4 The home PC with a dial-up connection
3.4.1 Assumptions/how the software works
3.4.2 Typical configuration files.
3.5 Other important configuration options
4 Usage reference
4.1 Starting chronyd
4.2 The chronyd configuration file
4.2.1 Comments in the configuration file
4.2.2 acquisitionport
4.2.3 allow
4.2.4 bindaddress
4.2.5 bindcmdaddress
4.2.6 broadcast
4.2.7 cmdallow
4.2.8 cmddeny
4.2.9 commandkey
4.2.10 cmdport
4.2.11 deny
4.2.12 driftfile
4.2.13 dumpdir
4.2.14 dumponexit
4.2.15 initstepslew
4.2.16 keyfile
4.2.17 local
4.2.18 linux_hz
4.2.19 linux_freq_scale
4.2.20 log
4.2.20.1 Measurements log file format
4.2.20.2 Statistics log file format
4.2.20.3 Tracking log file format
4.2.20.4 Real-time clock log file format
4.2.21 logchange
4.2.22 logdir
4.2.23 mailonchange
4.2.24 manual
4.2.25 maxupdateskew
4.2.26 noclientlog
4.2.27 peer
4.2.28 pidfile
4.2.29 port
4.2.30 rtcdevice
4.2.31 rtcfile
4.2.32 rtconutc
4.2.33 server
4.3 Running chronyc
4.3.1 Basic use
4.3.2 Command line options
4.3.3 Security with chronyc
4.3.4 Command reference
4.3.4.1 accheck
4.3.4.2 activity
4.3.4.3 add peer
4.3.4.4 add server
4.3.4.5 allow
4.3.4.6 allow all
4.3.4.7 burst
4.3.4.8 clients
4.3.4.9 cmdaccheck
4.3.4.10 cmdallow
4.3.4.11 cmdallow all
4.3.4.12 cmddeny
4.3.4.13 cmddeny all
4.3.4.14 cyclelogs
4.3.4.15 delete
4.3.4.16 deny
4.3.4.17 deny all
4.3.4.18 dump
4.3.4.19 exit
4.3.4.20 help
4.3.4.21 local
4.3.4.22 makestep
4.3.4.23 manual
4.3.4.24 maxdelay
4.3.4.25 maxdelayratio
4.3.4.26 maxpoll
4.3.4.27 maxupdateskew
4.3.4.28 minpoll
4.3.4.29 offline
4.3.4.30 online
4.3.4.31 password
4.3.4.32 quit
4.3.4.33 rtcdata
4.3.4.34 settime
4.3.4.35 sources
4.3.4.36 sourcestats
4.3.4.37 tracking
4.3.4.38 trimrtc
4.3.4.39 writertc
Appendix A Porting guide
A.1 System driver files
A.2 Quirks of particular systems
A.2.1 Linux
A.2.2 Solaris 2.5
A.2.3 SunOS 4.1.4
Appendix B GNU General Public License
|