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<TITLE>Exim Specification - 52. Day-to-day management</TITLE>
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Go to the <A HREF="spec_1.html">first</A>, <A HREF="spec_51.html">previous</A>, <A HREF="spec_53.html">next</A>, <A HREF="spec_59.html">last</A> section, <A HREF="spec_toc.html">table of contents</A>.
<P><HR><P>
<H1><A NAME="SEC864" HREF="spec_toc.html#TOC864">52. Day-to-day management</A></H1>
<P>
This chapter describes some of the regular tasks that need to be done to keep
Exim running smoothly.
</P>
<P>
<H2><A NAME="SEC865" HREF="spec_toc.html#TOC865">52.1 The panic log</A></H2>
<P>
When certain disasters occur, Exim writes entries to its panic log. These are
often copied to the main log as well, but can get lost amid the mass of other
entries. The panic log should be empty under normal circumstances. It is
therefore a good idea to check it (or to have a <EM>cron</EM> script check it)
regularly, in order to become aware of any problems.
</P>
<H2><A NAME="SEC866" HREF="spec_toc.html#TOC866">52.2 The reject log</A></H2>
<P>
<A NAME="IDX1912"></A>
If checking of sender addresses on incoming mail is enabled, the headers of
rejected messages are written to the reject log. Other policy rejections also
cause entries in this log, which should be regularly inspected to ensure that
the checking is working properly, and to pick up errors such as missing DNS
entries.
</P>
<H2><A NAME="SEC867" HREF="spec_toc.html#TOC867">52.3 Log cycling</A></H2>
<P>
<A NAME="IDX1913"></A>
The <EM>exicyclog</EM> script (see chapter 53) cycles the names of log files,
compresses all but the most recent, and deletes the oldest. This should be run
at intervals dependent on the amount of mail traffic. For a system with a
reasonable amount of mail, running it daily via <EM>cron</EM> is suggested.
</P>
<H2><A NAME="SEC868" HREF="spec_toc.html#TOC868">52.4 Statistics</A></H2>
<P>
The <EM>eximstats</EM> script (see chapter 53) produces statistics about
messages received and delivered, by analysing log files.
</P>
<H2><A NAME="SEC869" HREF="spec_toc.html#TOC869">52.5 What is Exim doing?</A></H2>
<P>
<A NAME="IDX1914"></A>
<A NAME="IDX1915"></A>
<A NAME="IDX1916"></A>
On systems that can restart a system call after receiving a signal, Exim
responds to the SIGUSR1 signal by writing a line describing what it is
doing to
the file <EM>exim-process.info</EM> in its spool directory.
The <EM>exiwhat</EM> script (see chapter 53) sends the signal to all Exim
processes it can find, having first emptied the
file.
It then waits for one second to allow the Exim processes to react before
displaying the results. In order to run <EM>exiwhat</EM> successfully you have to have
sufficient privilege to send the signal to the Exim processes, so it is
normally run as root.
</P>
<P>
When the number of processes handling incoming SMTP calls is limited by setting
the
<A NAME="IDX1917"></A>
<EM>smtp_accept_max</EM> option, the daemon uses the SIGCHLD signal to
detect when any of its subprocesses finishes. On some operating systems
this signal sometimes gets lost when the system is very busy.
However, Exim's daemon cleans up subprocesses every time it wakes up, so even
if SIGCHLD doesn't happen, the completion of subprocesses should
eventually get noticed.
</P>
<H2><A NAME="SEC870" HREF="spec_toc.html#TOC870">52.6 Changing the configuration</A></H2>
<P>
<A NAME="IDX1918"></A>
<A NAME="IDX1919"></A>
<A NAME="IDX1920"></A>
A changed configuration file is picked up immediately by any Exim processes
that are subsequently started, and by any existing process that re-execs Exim,
but it will not be noticed by any existing processes. The daemon process can be
caused to restart itself by sending it the SIGHUP signal, which should also
be sent when a new version of the Exim binary is installed. Restarting causes
its process id to change.
<A NAME="IDX1921"></A>
<A NAME="IDX1922"></A>
The current process id is written to a file whose name depends on the type of
daemon being run. By default, the file is written in Exim's spool directory,
but a compile-time configuration of PID_FILE_PATH can be used to cause it
to be placed elsewhere. When the daemon is both listening for incoming SMTP on
the standard port and periodically starting queue runner processes, the file is
called <EM>exim-daemon.pid</EM>. If it is doing only one of these things, the option
that started it (either -<EM>bd</EM> or -<EM>q<<EM>time</EM>></EM>) is added to the file name. It is
not necessary to use SIGHUP when changing the contents of any files
referred to in the configuration (for example, alias files) since each delivery
process reads such files independently.
</P>
<H2><A NAME="SEC871" HREF="spec_toc.html#TOC871">52.7 Watching the queue</A></H2>
<P>
The queue of messages awaiting delivery can be examined by running the Exim
monitor (see chapter 54), or by obeying <EM>exim -bp</EM> (or its
variants) periodically. The <EM>exiqsumm</EM> utility script can be called to obtain a
summary of the waiting messages for each domain, sorted by domain, age, or
message count.
</P>
<P>
<A NAME="IDX1923"></A>
If any messages are frozen, their header files and message log files should be
examined to determine the cause of the problem. Once the problem is believed to
be fixed, the messages can be unfrozen by the administrator, who can also kick
off an immediate delivery attempt, and also change recipient and sender
addresses if necessary.
<font color=green>
There are a number of command line options whose names begin with -<EM>M</EM> for
doing these things, and they can also be done from the Exim monitor.
</font>
</P>
<H2><A NAME="SEC872" HREF="spec_toc.html#TOC872">52.8 Holding domains</A></H2>
<P>
The option <EM>hold_domains</EM> allows mail for particular domains to be held on the
queue manually. This option is intended as a temporary operational measure
for delaying the delivery of mail while some problem is being sorted out, or
some new configuration tested.
</P>
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