Provided by: dovecot-core_2.2.22-1ubuntu2_amd64 bug


       doveadm-sync - Dovecot's two-way mailbox synchronization utility
       doveadm-backup - Dovecot's one-way mailbox synchronization utility


       doveadm  [-Dv]  sync  [-u  user|-A|-F  file]  [-S  socket_path]  [-1fPRU]  [-l  secs]  [-r
       rawlog_path] [-m mailbox] [-g mailbox_guid] [-n namespace|-N] [-x exclude] [-s state]  [-T
       secs] -d|destination

       doveadm  [-Dv]  backup  [-u  user|-A|-F  file]  [-S  socket_path]  [-fPRU]  [-l  secs] [-r
       rawlog_path] [-m mailbox] [-g mailbox_guid] [-n namespace|-N] [-x exclude] [-s state]  [-T
       secs] -d|destination


       dsync  is Dovecot's mailbox synchronization utility.  It can be used for several different
       use cases: Two-way synchronization of mailboxes, creating backups of  mails,  and  convert
       mailboxes  from/to  different  mailbox  formats.  All of these can be used within the same
       server or between different servers (via ssh(1) or tcp connections).  Remote mailboxes can
       be  accessed  also  via  IMAP  protocol,  which  allows  using dsync for mailbox migration

       You can run dsync in one of three modes:

              •      doveadm backup performs one-way synchronization.  If there are  any  changes
                     in  the  destination  they  will  be  deleted,  so the destination will look
                     exactly like the source.

              •      doveadm sync  performs  two-way  synchronization.   It  merges  all  changes
                     without  losing  anything.  Both the mailboxes will end up looking identical
                     after the synchronization is finished.

              •      doveadm sync -1 performs one-way synchronization, but it merges the  changes
                     in  destination  without  deleting  anything.   This  doesn't currently work
                     perfectly, so its use should be limited.  Its main purpose  is  that  during
                     mailbox  migration  you  can  run doveadm backup multiple times, then switch
                     mails to be delivered to the new mailbox and run doveadm sync -1  once  more
                     to transfer any last new mails from the old mailbox.

       There are also three different synchronization algorithms:

              •      Full  synchronization  (-f  parameter) scans through all the messages in all
                     the mailboxes.  This guarantees that everything will  be  synchronized,  but
                     it's unnecessarily slow for incremental synchronization.

              •      Fast  synchronization  (default)  first attempts to find mailboxes that have
                     changed,  and  synchronize  only  those.   This  is  done  by  checking  the
                     mailboxes'  metadata  (NEXTUID and HIGHESTMODSEQ).  Usually this works fine,
                     especially with one-way synchronization, but if both sides  do  exactly  the
                     same  number  of changes, the metadata may end up containing the same values
                     even if the changes were different.

              •      Stateful synchronization  (-s  parameter)  is  the  most  efficient  way  to
                     synchronize  mailboxes.   It  relies on having the earlier dsync run's state
                     saved somewhere and being passed to the next dsync run.  Based on this state
                     dsync  can send only the changes that happened after the previous dsync run.
                     As long as the state or the mailboxes aren't corrupted this algorithm should
                     work perfectly.  The replicator process uses this internally to perform most
                     of the synchronization.

       The syncing is done as perfectly as possible: an IMAP or a POP3 client shouldn't  be  able
       to notice any differences between the two mailboxes.  Two-way syncing means that it's safe
       to do any kind of modifications in both sides, and dsync will merge  the  changes  without
       losing  any  changes  done  on  either  side.   This  is possible because dsync can access
       Dovecot's index logs that keep  track  of  changes.   It's  of  course  possible  to  have
       conflicts during merging, these are resolved in a safe way.  See the dsync design document
       for more information.

       dsync uses the same configuration files as the rest of Dovecot (via  doveconf(1)  binary).
       The  entire  configuration  can be changed by giving -c parameter to another configuration
       file, or using -o parameter to override specific settings.  When executing a remote  dsync
       program it works the same way: it uses its own local configuration.

       dsync  can  be run completely standalone.  It doesn't require any Dovecot server processes
       to be running, except when using -u parameter to do a userdb lookup from auth process.

       dsync can sync either one or multiple users using the -u or -A parameters.  For continuous
       replication  you  can  use  the Dovecot replicator process, which automatically runs dsync
       whenever messages have changed.


       Global doveadm(1) options:

       -D     Enables verbosity and debug messages.

       -o setting=value
              Overrides the configuration setting from  /etc/dovecot/dovecot.conf  and  from  the
              userdb with the given value.  In order to override multiple settings, the -o option
              may be specified multiple times.

       -v     Enables verbosity, including progress counter.

       Command specific options:

       -1     Do one-way synchronization instead of two-way synchronization.

       -A     If the -A option is present, the command will be performed for  all  users.   Using
              this option in combination with system users from userdb { driver = passwd } is not
              recommended, because it  contains  also  users  with  a  lower  UID  than  the  one
              configured with the first_valid_uid setting.

              When  the  SQL  userdb  module  is used make sure that the iterate_query setting in
              /etc/dovecot/dovecot-sql.conf.ext matches your database  layout.   When  using  the
              LDAP userdb module, make sure that the iterate_attrs and iterate_filter settings in
              /etc/dovecot/dovecot-ldap.conf.ext match your LDAP  schema.   Otherwise  doveadm(1)
              will be unable to iterate over all users.

       -F file
              Execute  the  command  for  all  the  users in the file.  This is similar to the -A
              option, but instead of getting the list of users from the  userdb,  they  are  read
              from the given file.  The file contains one username per line.

       -N     Synchronize  all  the  available namespaces.  By default only namespaces that don't
              have explicit location setting are synchronized.

       -P     Run a doveadm-purge(1) for the destination (remote) storage after synchronization.

       -R     Do a reverse sync. Normally, messages would be pushed from the local system to  the
              destination (remote). This option reverses the flow, and will instead pull messages
              from the remote to the local storage.

       -S socket_path
              The option's argument is either an absolute path to a local UNIX domain socket,  or
              a  hostname  and  port (hostname:port), in order to connect a remote host via a TCP

              This allows an administrator to execute doveadm(1) mail commands through the  given

       -T secs
              Specify  the  time  in  seconds,  how  long  doveadm(1) should wait for stalled I/O
              operations.  The default timeout is 600 seconds.

       -U     This  is  used  internally  by  replicator  to  have  dsync  notify  it  when   the
              synchronization is finished.

       -d     Use  the default destination, which is looked up from the mail_replica userdb extra

       -g mailbox_guid
              Same as -m, but find the mailbox to be synchronized by its GUID instead of by name.

       -l secs
              Lock the dsync for this user.  Wait  for  maximum  secs  before  giving  up.   This
              parameter  should  be  used  to  avoid broken synchronization if it's possible that
              dsync is being run concurrently for the same user.

       -m mailbox
              Synchronize only this mailbox name.

       -n namespace
              Synchronize only the specified namespace.  This  parameter  can  be  used  multiple

       -r rawlog_path
              Running  dsync remotely, write the remote input/output traffic to the specified log

       -s previous_state
              Use stateful synchronization.  If the previous  state  is  unknown,  use  an  empty
              string.  The new state is always printed to standard output.

       -u user/mask
              Run  the  command  only  for the given user.  It's also possible to use '*' and '?'
              wildcards (e.g. -u *
              When neither the -A option, nor the -F file option, nor the -u user was  specified,
              the command will be executed with the environment of the currently logged in user.

       -x mailbox_mask
              Exclude  the  specified  mailbox  name/mask.   The  mask  may  contain  "?" and "*"
              wildcards.  This parameter can be used multiple times.


              This argument specifies the synchronized destination.  It can be one of:

                     Same as mail_location setting, e.g. maildir:~/Maildir

                     Uses dsync_remote_cmd setting to connect to the  remote  host  (usually  via

                     This  is  the  same  as  remote, except "user@domain\n" is sent before dsync
                     protocol starts.  This allows implementing a  trusted  wrapper  script  that
                     runs doveadm dsync-server by reading the username from the first line.

                     Connects to remote doveadm server via TCP.  The default port is specified by
                     doveadm_port setting.

                     This is the same as tcp, but with SSL.


       dsync will exit with one of the following values:

       0   Synchronization was done perfectly.

       2   Synchronization was done without errors, but some changes couldn't  be  done,  so  the
           mailboxes  aren't  perfectly  synchronized.  Running  dsync  again usually fixes this.
           Typically this occurs for message modification sequences with newly created mailboxes.
           It can also occur if one of the mailboxes change during the syncing.

       1, >2
           Synchronization failed.


       Synchronize mailboxes with a remote server.  Any errors are written to stderr.

              doveadm sync -u

       If you need more complex parameters to ssh, you can use e.g.:

              doveadm sync -u ssh -i id_dsa.dovecot \
     doveadm dsync-server -u

       Assuming  that  the  mail_location  setting in /etc/dovecot/conf.d/10-mail.conf is set to:
       mail_location = mdbox:~/mdbox, a logged in system user may convert her/his mails from  its
       Maildir  in  her/his  home directory to the mdbox mailbox format.  The user has to execute
       the command:

              doveadm sync maildir:~/Maildir

       If you want to do this without any downtime, you can do the conversion one user at a time.

           •   Configuration uses mail_location = maildir:~/Maildir

           •   Set up the possibility of doing per-user mail location using userdb extra fields.

       Then for each user:

           1.  Run doveadm sync once to do the initial conversion.

           2.  Run  doveadm  sync  again, because the initial conversion could have taken a while
               and new changes could have occurred during it.   This  second  time  only  applies
               changes, so it should be fast.

           3.  Update  mail  extra field in userdb to mdbox:~/mdbox.  If you're using auth cache,
               you need to flush it, e.g.  doveadm auth cache flush.

           4.  Wait for a few seconds and then kill (doveadm kick) the user's all  existing  imap
               and pop3 sessions (that are still using maildir).

           5.  Run  doveadm sync once more to apply final changes that were possibly done.  After
               this there should be no changes to Maildir, because the user's mail  location  has
               been changed and all existing processes using it have been killed.

       Once  all  users  have  been converted, you can set the default mail_location to mdbox and
       remove the per-user mail locations from userdb.


       Report   bugs,   including   doveconf   -n   output,   to   the   Dovecot   Mailing   List
       <>.     Information    about    reporting   bugs   is   available   at:


       doveadm(1), doveadm-auth(1), doveadm-kick(1), doveadm-purge(1), doveconf(1)

       Additional resources:

       dsync design