SYNC_CLIENT(8) Cyrus IMAP SYNC_CLIENT(8)

sync_client - Cyrus IMAP documentation

Client side of the synchronization (replication) engine

sync_client [ -v ] [ -l ] [ -L ] [ -z ] [ -C config-file ] [ -S server-name ]
    [ -f input-file ] [ -F shutdown_file ] [ -w wait_interval ]
    [ -t timeout ] [ -d delay ] [ -r ] [ -n channel ] [ -u ] [ -m ]
    [ -p partition ] [ -A ] [ -N ] [ -s ] [ -O ] objects...


sync_client is the client side of the replication system. It runs on the client (master) system and connects to the target (replica) system and generates an appropriate sequence of transactions to synchronize the replica system with the master system.

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

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

All users mode. Sync every user on the server to the replica (doesn't do non-user mailboxes at all... this could be considered a bug and maybe it should do those mailboxes independently)

Minimum delay between replication runs in rolling replication mode. Larger values provide better efficiency as transactions can be merged. Smaller values mean that the replica system is more up to date and that you don't end up with large blocks of replication transactions as a single group. Default: 3 seconds.

In mailbox or user replication mode: provides list of users or mailboxes to replicate. In rolling replication mode, specifies an alternate log file (sync_client will exit after processing the log file).

Rolling replication checks for this file at the end of each replication cycle and shuts down if it is present. Used to request a nice clean shutdown at the first convenient point. The file is removed on shutdown. Overrides sync_shutdown_file option in imapd.conf(5).

Verbose logging mode.

Perform only local mailbox operations (do not do mupdate operations). This feature was introduced in version 3.0.

Mailbox mode. Remaining arguments are list of mailboxes which should be replicated.

Use the named channel for rolling replication mode. If multiple channels are specified in sync_log_channels then use one of them. This option is probably best combined with -S to connect to a different server with each channel.

Use non-blocking sync_lock (combination of IP address and username) to skip over any users who are currently syncing.

Only attempt to connect to the backend server once.

Without this option, sync_client will retry failed connections indefinitely, waiting up to sync_reconnect_maxwait (default: 20m) between attempts.


No copyback mode. Replication will stop if the replica reports a CRC error, rather than doing a full mailbox sync. Useful if moving users to a new server, where you don't want any errors to cause the source servers to change the account.

In mailbox or user replication mode: provides the name of the partition on the replica to which the mailboxes/users should be replicated.

Rolling (repeat) replication mode. Pick up a list of actions recorded by the lmtpd(8), imapd(8), pop3d(8) and nntpd(8) daemons from the file specified in sync_log_file. Repeat until sync_shutdown_file appears. Alternative log and shutdown files can be specified with -f and -F.

In this invocation, sync_client will background itself to run as a daemon.


As for -r, but without backgrounding.

-1, --rolling-once
As for -R, but only process a single log file before exiting.

Sieve mode. Remaining arguments are list of users whose Sieve files should be replicated. Principally used for debugging purposes: not exposed to sync_client(8).

Tells sync_client with which server to communicate. Overrides the sync_host configuration option.

Timeout for single replication run in rolling replication. sync_client will negotiate a restart after this many seconds. Default: 600 seconds

User mode. Remaining arguments are list of users who should be replicated.

Verbose mode. Use twice (-v -v) to log all protocol traffic to stderr.

Wait this long before starting. This option is typically used so that we can attach a debugger to one end of the replication system or the other.

Require compression. The replication protocol will always try to enable deflate compression if both ends support it. Set this flag when you want to abort if compression is not available.

Request the stage-to-archive feature. If the remote end has the archive_enabled option set, then it will stage incoming replication on the archive partition instead of the spool partition. If the remote end does not support it, replication will proceed as though -a was not provided. This option is useful when standing up a new replica of an existing server, as most of the stored mail is likely older than the archive threshold and so is destined for the archive partition anyway. By staging on that partition, Cyrus can avoid a cross-partition copy for every message.

On a replication master, the following would be added to the START section of cyrus.conf(5):

syncclient              cmd="/usr/lib/cyrus/bin/sync_client -r"




[NB: More examples needed]

The -L feature, local updates only, was added in version 3.0.

/etc/imapd.conf

sync_server(8), cyrus.conf(5), imapd.conf(5), master(8)

The Cyrus Team, David Carter (dpc22@cam.ac.uk), Ken Murchison (ken@oceana.com), Nic Bernstein (Onlight)

1993–2025, The Cyrus Team

January 22, 2025 3.10.1