Provided by: dovecot-core_2.3.19.1+dfsg1-2ubuntu2_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] [-a all  mailbox]  [-s
       state] [-T secs] [-t start date] [-e end date] [-O sync flag] [-I max size] -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] [-a all  mailbox]  [-s
       state] [-T secs] [-t start date] [-e end date] [-O sync flag] [-I max size] -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.

                     The  one-way  algorithm  is  the  same as two-way dsync algorithm except the
                     source account is not modified. It fetches the message's GUID (Global  UID),
                     which  is  used to identify any conflicting UIDs in messages. As long as the
                     source and destination side has matching UID<->GUID  mapping,  those  emails
                     are  assumed  to  be  synced  correctly.  Only after the first mismatch will
                     changes begin.

                     Example: Source mailbox has messages UID  1..5;  source  mailbox  is  sync'd
                     using doveadm backup to the destination. Subsequently, UID 6 is delivered to
                     the source mailbox and UID 1 is expunged from the  destination  mailbox.  In
                     this  example,  UID 1 is kept removed (in destination) because UID 1..5 have
                     identical Date+Message-ID headers. UID 6 is not seen in destination so  it's

                     If  both  source and destination have UID 6, but the messages are different,
                     the headers don't match and both the messages are kept  in  the  destination
                     but  they're  given  new  UIDs 7 and 8 just to be sure any client didn't get
                     confused about what UID 6 actually was. Thus, one-way sync begins to quickly
                     diverge  from the source mailbox once changes start to occur on either side;
                     one-way sync should therefore normally only be used within a short period of
                     time  after a doveadm backup or doveadm sync command was used to synchronize
                     the mailboxes.

       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:

       -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.

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

       -f     Do full synchronization.

       -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

       -a all mailbox
              Name for the "All mails" virtual mailbox. If specified, mails are attempted  to  be
              copied  from  this  mailbox  instead of being saved separately. This may reduce the
              total disk space usage as well as disk IO.

       -t start date
              Skip any mails whose received-timestamp is older than the specified time.

       -e end date
              Skip any mails whose received-timestamp is newer than the specified time.

       -O sync flag
              Sync only mails that have the specified flag.  If the flag name  begins  with  "-",
              sync all mails except the ones with the specified flag.

       -I max size
              Skip any mails larger than the specified size.

       -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.  The mask can also be a special-use name (e.g. \Trash).  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.

              command [arg1 [, arg2, ...]]
                     Runs  a  local  command that connects its standard input & output to a dsync


       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