File: uri.html

package info (click to toggle)
libvirt 5.6.0-2
  • links: PTS, VCS
  • area: main
  • in suites: bullseye
  • size: 240,844 kB
  • sloc: ansic: 584,521; xml: 176,725; sh: 9,912; python: 4,731; perl: 4,343; makefile: 3,321; ml: 465
file content (404 lines) | stat: -rw-r--r-- 15,012 bytes parent folder | download | duplicates (2)
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
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
  <!--
        This file is autogenerated from uri.html.in
        Do not edit this file. Changes will be lost.
      -->
  <!--
        This page was generated at Tue Jul 30 02:04:26 UTC 2019.
      -->
  <head>
    <meta charset="UTF-8"/>
    <meta name="viewport" content="width=device-width, initial-scale=1"/>
    <link rel="stylesheet" type="text/css" href="main.css"/>
    <link rel="apple-touch-icon" sizes="180x180" href="/apple-touch-icon.png"/>
    <link rel="icon" type="image/png" sizes="32x32" href="/favicon-32x32.png"/>
    <link rel="icon" type="image/png" sizes="16x16" href="/favicon-16x16.png"/>
    <link rel="manifest" href="/manifest.json"/>
    <meta name="theme-color" content="#ffffff"/>
    <title>libvirt: Connection URIs</title>
    <meta name="description" content="libvirt, virtualization, virtualization API"/>
    <script type="text/javascript" src="js/main.js">
      <!--// forces non-empty element-->
    </script>
  </head>
  <body onload="pageload()">
    <div id="body">
      <div id="content">
        <h1>Connection URIs</h1>
        <ul>
          <li>
            <a href="#URI_libvirt">Specifying URIs to libvirt</a>
          </li>
          <li>
            <a href="#URI_config">Configuring URI aliases</a>
          </li>
          <li>
            <a href="#URI_default">Default URI choice</a>
          </li>
          <li>
            <a href="#URI_virsh">Specifying URIs to virsh, virt-manager and virt-install</a>
          </li>
          <li>
            <a href="#URI_xen">xen:///system URI</a>
          </li>
          <li>
            <a href="#URI_qemu">qemu:///... QEMU and KVM URIs</a>
          </li>
          <li>
            <a href="#URI_remote">Remote URIs</a>
          </li>
          <li>
            <a href="#URI_test">test:///... Test URIs</a>
          </li>
          <li>
            <a href="#URI_legacy">Other &amp; legacy URI formats</a>
            <ul>
              <li>
                <a href="#URI_NULL">NULL and empty string URIs</a>
              </li>
              <li>
                <a href="#URI_legacy_xen">Legacy: </a>
              </li>
            </ul>
          </li>
        </ul>
        <p>
Since libvirt supports many different kinds of virtualization
(often referred to as "drivers" or "hypervisors"), we need a
way to be able to specify which driver a connection refers to.
Additionally we may want to refer to a driver on a remote
machine over the network.
</p>
        <p>
To this end, libvirt uses URIs as used on the Web and as defined in <a href="http://www.ietf.org/rfc/rfc2396.txt">RFC 2396</a>. This page
documents libvirt URIs.
</p>
        <h2>
          <a id="URI_libvirt">Specifying URIs to libvirt</a>
          <a class="headerlink" href="#URI_libvirt" title="Permalink to this headline">¶</a>
        </h2>
        <p>
      The URI is passed as the <code>name</code> parameter to
      <a href="html/libvirt-libvirt-host.html#virConnectOpen"><code>virConnectOpen</code></a>
      or
      <a href="html/libvirt-libvirt-host.html#virConnectOpenReadOnly"><code>virConnectOpenReadOnly</code></a>.
      For example:
</p>
        <pre>
virConnectPtr conn = virConnectOpenReadOnly (<b>"test:///default"</b>);
</pre>
        <h2>
          <a id="URI_config">Configuring URI aliases</a>
          <a class="headerlink" href="#URI_config" title="Permalink to this headline">¶</a>
        </h2>
        <p>
To simplify life for administrators, it is possible to setup URI aliases in a
libvirt client configuration file. The configuration file is <code>/etc/libvirt/libvirt.conf</code>
for the root user, or <code>$XDG_CONFIG_HOME/libvirt/libvirt.conf</code> for any unprivileged user.
In this file, the following syntax can be used to setup aliases
    </p>
        <pre>
uri_aliases = [
  "hail=qemu+ssh://root@hail.cloud.example.com/system",
  "sleet=qemu+ssh://root@sleet.cloud.example.com/system",
]
</pre>
        <p>
  A URI alias should be a string made up from the characters
  <code>a-Z, 0-9, _, -</code>. Following the <code>=</code>
  can be any libvirt URI string, including arbitrary URI parameters.
  URI aliases will apply to any application opening a libvirt
  connection, unless it has explicitly passed the <code>VIR_CONNECT_NO_ALIASES</code>
  parameter to <code>virConnectOpenAuth</code>. If the passed in
  URI contains characters outside the allowed alias character
  set, no alias lookup will be attempted.
</p>
        <h2>
          <a id="URI_default">Default URI choice</a>
          <a class="headerlink" href="#URI_default" title="Permalink to this headline">¶</a>
        </h2>
        <p>
If the URI passed to <code>virConnectOpen*</code> is NULL, then libvirt will use the following
logic to determine what URI to use.
</p>
        <ol>
          <li>The environment variable <code>LIBVIRT_DEFAULT_URI</code></li>
          <li>The client configuration file <code>uri_default</code> parameter</li>
          <li>Probe each hypervisor in turn until one that works is found</li>
        </ol>
        <h2>
          <a id="URI_virsh">Specifying URIs to virsh, virt-manager and virt-install</a>
          <a class="headerlink" href="#URI_virsh" title="Permalink to this headline">¶</a>
        </h2>
        <p>
In virsh use the <code>-c</code> or <code>--connect</code> option:
</p>
        <pre>
virsh <b>-c test:///default</b> list
</pre>
        <p>
If virsh finds the environment variable
<code>VIRSH_DEFAULT_CONNECT_URI</code> set, it will try this URI by
default. Use of this environment variable is, however, deprecated
now that libvirt supports <code>LIBVIRT_DEFAULT_URI</code> itself.
</p>
        <p>
When using the interactive virsh shell, you can also use the
<code>connect</code> <i>URI</i> command to reconnect to another
hypervisor.
</p>
        <p>
In virt-manager use the <code>-c</code> or <code>--connect=</code><i>URI</i> option:
</p>
        <pre>
virt-manager <b>-c test:///default</b>
</pre>
        <p>
In virt-install use the <code>--connect=</code><i>URI</i> option:
</p>
        <pre>
virt-install <b>--connect=test:///default</b> <i>[other options]</i>
</pre>
        <h2>
          <a id="URI_xen">xen:///system URI</a>
          <a class="headerlink" href="#URI_xen" title="Permalink to this headline">¶</a>
        </h2>
        <p>
          <i>This section describes a feature which is new in libvirt &gt;
0.2.3.  For libvirt ≤ 0.2.3 use <a href="#URI_legacy_xen"><code>"xen"</code></a>.</i>
        </p>
        <p>
To access a Xen hypervisor running on the local machine
use the URI <code>xen:///system</code>.
</p>
        <h2>
          <a id="URI_qemu">qemu:///... QEMU and KVM URIs</a>
          <a class="headerlink" href="#URI_qemu" title="Permalink to this headline">¶</a>
        </h2>
        <p>
To use QEMU support in libvirt you must be running the
<code>libvirtd</code> daemon (named <code>libvirt_qemud</code>
in releases prior to 0.3.0).  The purpose of this
daemon is to manage qemu instances.
</p>
        <p>
The <code>libvirtd</code> daemon should be started by the
init scripts when the machine boots. It should appear as
a process <code>libvirtd --daemon</code> running as root
in the background and will handle qemu instances on behalf
of all users of the machine (among other things). </p>
        <p>
So to connect to the daemon, one of two different URIs is used:
</p>
        <ul>
          <li><code>qemu:///system</code> connects to a system mode daemon. </li>
          <li><code>qemu:///session</code> connects to a session mode daemon. </li>
        </ul>
        <p>
(If you do <code>libvirtd --help</code>, the daemon will print
out the paths of the Unix domain socket(s) that it listens on in
the various different modes).
</p>
        <p>
KVM URIs are identical.  You select between qemu, qemu accelerated and
KVM guests in the <a href="format.html#KVM1">guest XML as described
here</a>.
</p>
        <h2>
          <a id="URI_remote">Remote URIs</a>
          <a class="headerlink" href="#URI_remote" title="Permalink to this headline">¶</a>
        </h2>
        <p>
Remote URIs are formed by taking ordinary local URIs and adding a
hostname and/or transport name. As a special case, using a URI
scheme of 'remote', will tell the remote libvirtd server to probe
for the optimal hypervisor driver. This is equivalent to passing
a NULL URI for a local connection. For example:
</p>
        <table class="top_table">
          <tr>
            <th> Local URI </th>
            <th> Remote URI </th>
            <th> Meaning </th>
          </tr>
          <tr>
            <td>
              <code>xen:///system</code>
            </td>
            <td>
              <code>xen://oirase/system</code>
            </td>
            <td> Connect to the Xen hypervisor running on host <code>oirase</code>
  using TLS. </td>
          </tr>
          <tr>
            <td>
              <code>NULL</code>
            </td>
            <td>
              <code>remote://oirase/</code>
            </td>
            <td> Connect to the "default" hypervisor running on host <code>oirase</code>
  using TLS. </td>
          </tr>
          <tr>
            <td>
              <code>xen:///system</code>
            </td>
            <td>
              <code>xen+ssh://oirase/system</code>
            </td>
            <td> Connect to the Xen hypervisor running on host <code>oirase</code>
  by going over an <code>ssh</code> connection. </td>
          </tr>
          <tr>
            <td>
              <code>test:///default</code>
            </td>
            <td>
              <code>test+tcp://oirase/default</code>
            </td>
            <td> Connect to the test driver on host <code>oirase</code>
  using an unsecured TCP connection. </td>
          </tr>
        </table>
        <p>
Remote URIs in libvirt offer a rich syntax and many features.
We refer you to <a href="remote.html#Remote_URI_reference">the libvirt
remote URI reference</a> and <a href="remote.html">full documentation
for libvirt remote support</a>.
</p>
        <h2>
          <a id="URI_test">test:///... Test URIs</a>
          <a class="headerlink" href="#URI_test" title="Permalink to this headline">¶</a>
        </h2>
        <p>
The test driver is a dummy hypervisor for test purposes.
The URIs supported are:
</p>
        <ul>
          <li><code>test:///default</code> connects to a default set of
host definitions built into the driver. </li>
          <li><code>test:///path/to/host/definitions</code> connects to
a set of host definitions held in the named file.
</li>
        </ul>
        <h2>
          <a id="URI_legacy">Other &amp; legacy URI formats</a>
          <a class="headerlink" href="#URI_legacy" title="Permalink to this headline">¶</a>
        </h2>
        <h3>
          <a id="URI_NULL">NULL and empty string URIs</a>
          <a class="headerlink" href="#URI_NULL" title="Permalink to this headline">¶</a>
        </h3>
        <p>
Libvirt allows you to pass a <code>NULL</code> pointer to
<code>virConnectOpen*</code>.  Empty string (<code>""</code>) acts in
the same way.  Traditionally this has meant
<q>connect to the local Xen hypervisor</q>.  However in future this
may change to mean <q>connect to the best available hypervisor</q>.
</p>
        <p>
The theory is that if, for example, Xen is unavailable but the
machine is running an OpenVZ kernel, then we should not try to
connect to the Xen hypervisor since that is obviously the wrong
thing to do.
</p>
        <p>
In any case applications linked to libvirt can continue to pass
<code>NULL</code> as a default choice, but should always allow the
user to override the URI, either by constructing one or by allowing
the user to type a URI in directly (if that is appropriate).  If your
application wishes to connect specifically to a Xen hypervisor, then
for future proofing it should choose a full <a href="#URI_xen"><code>xen:///system</code> URI</a>.
</p>
        <h3>
          <a id="URI_legacy_xen">Legacy: <code>"xen"</code></a>
          <a class="headerlink" href="#URI_legacy_xen" title="Permalink to this headline">¶</a>
        </h3>
        <p>
Another legacy URI is to specify name as the string
<code>"xen"</code>.  This will continue to refer to the Xen
hypervisor.  However you should prefer a full <a href="#URI_xen"><code>xen:///system</code> URI</a> in all future code.
</p>
      </div>
    </div>
    <div id="nav">
      <div id="home">
        <a href="index.html">Home</a>
      </div>
      <div id="jumplinks">
        <ul>
          <li>
            <a href="downloads.html">Download</a>
          </li>
          <li>
            <a href="contribute.html">Contribute</a>
          </li>
          <li>
            <a href="docs.html">Docs</a>
          </li>
        </ul>
      </div>
      <div id="search">
        <form id="simplesearch" action="https://www.google.com/search" enctype="application/x-www-form-urlencoded" method="get">
          <div>
            <input id="searchsite" name="sitesearch" type="hidden" value="libvirt.org"/>
            <input id="searchq" name="q" type="text" size="12" value=""/>
            <input name="submit" type="submit" value="Go"/>
          </div>
        </form>
        <div id="advancedsearch">
          <span>
            <input type="radio" name="what" id="whatwebsite" checked="checked" value="website"/>
            <label for="whatwebsite">Website</label>
          </span>
          <span>
            <input type="radio" name="what" id="whatwiki" value="wiki"/>
            <label for="whatwiki">Wiki</label>
          </span>
          <span>
            <input type="radio" name="what" id="whatdevs" value="devs"/>
            <label for="whatdevs">Developers list</label>
          </span>
          <span>
            <input type="radio" name="what" id="whatusers" value="users"/>
            <label for="whatusers">Users list</label>
          </span>
        </div>
      </div>
    </div>
    <div id="footer">
      <div id="contact">
        <h3>Contact</h3>
        <ul>
          <li>
            <a href="contact.html#email">email</a>
          </li>
          <li>
            <a href="contact.html#irc">irc</a>
          </li>
        </ul>
      </div>
      <div id="community">
        <h3>Community</h3>
        <ul>
          <li>
            <a href="https://twitter.com/hashtag/libvirt">twitter</a>
          </li>
          <li>
            <a href="http://stackoverflow.com/questions/tagged/libvirt">stackoverflow</a>
          </li>
          <li>
            <a href="http://serverfault.com/questions/tagged/libvirt">serverfault</a>
          </li>
        </ul>
      </div>
      <div id="conduct">
            Participants in the libvirt project agree to abide by <a href="governance.html#codeofconduct">the project code of conduct</a></div>
      <br class="clear"/>
    </div>
  </body>
</html>