This documentation is for Dovecot v2.x, see wiki1 for v1.x documentation.
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Both the client and the server also need to have a shared secret:

{{{
doveadm_password = secret
}}}

Replication with dsync

NOTE: v2.2 is highly recommended for this. Earlier versions can't do incremental metadata syncing. This means that the more mails a mailbox has, the slower it is to sync it.

NOTE2: sdbox/mdbox mailbox formats are recommended for replication. Maildir still has some issues (although probably not noticeable in normal use).

Make sure that user listing is configured for your userdb, this is required by replication:

doveadm user '*'

Enable the replication plugin:

mail_plugins = $mail_plugins notify replication

Replicator process should be started at startup, so it can start replicating users immediately:

service replicator {
  process_min_avail = 1
}

You need to configure how and where to replicate. Using SSH for example:

dsync_remote_cmd = ssh -l%{login} %{host} doveadm dsync-server -u%u
plugin {
  mail_replica = remote:vmail@anotherhost.example.com
}

The mail processes need to have access to the replication-notify fifo and socket. If you have a single vmail UID, you can do:

service aggregator {
  fifo_listener replication-notify-fifo {
    user = vmail
  }
  unix_listener replication-notify {
    user = vmail
  }
}

The replication-notify only notifies the replicator processes that there is work to be done, so it's not terribly insecure either to just set mode=0666.

dsync over TCP connections (v2.2+)

Create a listener for doveadm-server:

service doveadm {
  inet_listener {
    port = 12345
  }
}

And tell doveadm client to use this port by default:

doveadm_port = 12345

Both the client and the server also need to have a shared secret:

doveadm_password = secret

Now you can use tcp:hostname as the dsync target. You can also override the port with tcp:hostname:port.

SSL

You can also use SSL for the connection:

service doveadm {
  inet_listener {
    port = 12345
    ssl = yes
  }
}

The client must be able to verify that the SSL certificate is valid, so you need to specify the directory containing valid SSL CA roots:

ssl_client_ca_dir = /etc/ssl/certs

Now you can use tcps:hostname or tcps:hostname:port as the dsync target.

dsync wrapper script for root (v2.2+)

If you're using multiple UIDs, dsync needs to be started as root, which means you need to log in as root with ssh (or use sudo). Another possibility is to allow root to run only a wrapper script. There is some built-in support for this in v2.2+ to make it easier:

dovecot.conf:

dsync_remote_cmd = /usr/bin/ssh -i /root/.ssh/id_dsa.dsync %{host} /usr/local/bin/dsync-in-wrapper.sh
plugin {
  mail_replica = remoteprefix:vmail@anotherhost.example.com
}

/root/.ssh/authorized_keys2:

command="/usr/local/bin/dsync-in-wrapper.sh",no-port-forwarding,no-X11-forwarding,no-agent-forwarding,no-pty <ssh key>

/usr/local/bin/dsync-in-wrapper.sh:

read username
ulimit -c unlimited # for debugging any crashes
/usr/local/bin/doveadm dsync-server -u $username

None: Replication (last edited 2019-05-27 07:44:57 by AkiTuomi)