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master - Cyrus IMAP documentation

The Cyrus IMAP master process.


master [ -C config-file ] [ -M alternate cyrus.conf ]
    [ -l listen queue ] [ -p pidfile ] [ -P snmp agentx ping interval ]
    [ -j janitor period ] [ -d | -D ] [ -L logfile ]
    [ -x snmp agentx socket ]


master is the process that controls all of the Cyrus processes. This process is responsible for creating all imapd, pop3d, lmtpd and timsieved child processes. This process also performs scheduled cleanup/maintenance.

If this process dies, then no new sessions will be started.

It kills itself and all child processes when it receives a SIGTERM.

master reads its configuration options out of the imapd.conf(5) file unless specified otherwise by -C.


-C alternate imapd.conf
Use the specified configuration file config-file rather than the default imapd.conf(5).

-M alternate cyrus.conf
Specifies an alternate cyrus.conf for use by master.

-l listen queue backlog
Increase the listen queue backlog. By default, the listen queue is set to 32. On systems with a high connection rate, it may be desirable to increase this value. refer to listen(2) for details.

-j janitor full-sweeps per second
Sets the number of times per second the janitor should sweep the entire child table. Leave it at the default of 1 unless you have a really high fork rate (and you have not increased the child hash table size when you compiled Cyrus from its default of 10000 entries).

-p pidfile
Use pidfile as the pidfile. If not specified, defaults to /var/run/

-P snmp agentx ping interval
Sets the amount on time in seconds the subagent will try and reconnect to the master agent (snmpd) if it ever becomes (or starts) disconnected. Requires net-snmp 5.0 or higher.

Start in daemon mode (run in background and disconnect from controlling terminal).

Don't close stdin/stdout/stderr. Primarily useful for debugging. Note that -d and -D cannot be used together; consider using -L instead.

-L logfile
Redirect stdout and stderr to the given logfile.

-x snmp agentx socket
Address the master agent (most likely snmpd) listens on. Requires net-snmp 5.0 or higher.


Upon execution, master reads its configuration information out of the cyrus.conf(5) file, or an alternative if -M is used.

master rereads its configuration file when it receives a hangup signal, SIGHUP. Services and events may be added, deleted or modified when the configuration file is reread. Any active services removed from the configuration file will be allowed to run until completion. Services added or modified to listen on a privileged port may not be able to bind the port, depending on your system configuration. In this case a full restart is needed.

master propagates the hangup signal, SIGHUP, to its child service processes, so that they stop waiting for incoming connections and exit, allowing them to be recycled. This is useful to make services take into account a new version of the imapd.conf(5) file. Children that are servicing a client connection when SIGHUP is received are allowed to run until the client logouts before being recycled. It may take a long time until the client logouts, so a log message is generated for processes that have not been recycled within 30s.


The environment variable CYRUS_VERBOSE can be set to log additional debugging information. Setting the value to 1 results in base level logging. Setting it higher results in more log messages being generated.


/etc/cyrus.conf, /etc/imapd.conf, /var/run/


cyrus.conf(5), imapd.conf(5), imapd(8), pop3d(8), lmtpd(8), timsieved(8), idled(8)


The Cyrus Team, Nic Bernstein (Onlight)


1993-2018, The Cyrus Team
March 9, 2021 3.2.6