Hi,

I'm trying to set up some dsync based replication between two hosts on my network. The current topology is a single server running Postfix with a single dovecot installation with a Maildir per user (only 4 users including myself). No NFS, just local system users on ext4. I am only using system users, ie no virtual users. I am using dovecot deliver to deliver mails into the Maildir's. This - being a very standard Maildir installation - all works just fine.

I'm running dovecot-2.1.5 (release versions) x86_64 with Gentoo on both hosts and using key based ssh to transport the data using the root login.

What I would like to do is extend the design so as to replicate the Maildirs across a second machine and in the future be able to connect via IMAP into either machine to sync mail. Two way dsync would be rather cool because I could then deliver via SMTP to either system and have changes automagically propagate - but initially just simple replication would be a good start.

I was hoping that dsync would allow me to do this, but I've run into quite a number of problems while getting this to work.

http://dovecot.org/list/dovecot/2012-March/064243.html ...was very useful and I've based my config on that.

Initially I've tried to sync up the user Maildirs, and this has more or less worked:

doveadm sync -u lyn remote:root@dustbowl.reub.net

This succeeds without error on the initial sync.

However if I try to run the re-sync again (such as a use case of if the sync of another Maildir takes 4 hours so I want to resync up the earlier ones again) I end up with a mysteriously named INBOX folder in both the source and destination Maildirs:

drwx------ 5 lyn lyn 4096 Apr 30 19:32 .INBOX_7a86a62d465a974fb92f00003b258734

It has the basic structure of a Maildir but is empty in terms of mails:

drwx------ 2 lyn lyn 4096 Apr 30 19:32 cur -rw------- 1 lyn lyn 220 Apr 30 19:32 dovecot.index.log -rw------- 1 lyn lyn 51 Apr 30 19:32 dovecot-uidlist -rw------- 1 lyn lyn 0 Apr 30 19:32 maildirfolder drwx------ 2 lyn lyn 4096 Apr 30 19:32 new drwx------ 2 lyn lyn 4096 Apr 30 19:32 tmp

First question: why is this random named directory being created in the origin Maildir? Shouldn't the replication be more or less read-only in the origin Maildir?

Second question: If I re-attempt a doveadm sync a second time I get this error:

tornado Maildir # doveadm sync -u lyn remote:root@dustbowl.reub.net dsync-local(lyn): Error: Can't rename mailbox INBOX_7a86a62d465a974fb92f00003b258734 to INBOX: Target mailbox already exists dsync-local(lyn): Error: Can't rename mailbox INBOX to INBOX_eb15f30ea563be4b703200002bd68bb1: Renaming INBOX isn't supported. tornado Maildir #

It's not clear if the second attempt has failed or succeeded, and it's a bit odd that it errors out on a directory that the dovecot sync process itself has created.

Third question: Upon starting Dovecot lots of ugliness is logged in the mail log:

Apr 30 19:44:59 tornado dovecot: master: Dovecot v2.1.5 starting up (core dumps disabled) Apr 30 19:44:59 tornado dovecot: doveadm(mozsync): Error: user mozsync: Initialization failed: Namespace '': mkdir(/var/www/xxx/server-full/Maildir) failed: Permission denied (euid=1016(mozsync) egid=1016(<unknown>) missing +w perm: /var/www/xxx/server-full, dir owned by 0:0 mode=0755) Apr 30 19:44:59 tornado dovecot: doveadm(mozsync): Error: sync: User init failed Apr 30 19:44:59 tornado dovecot: doveadm(mozsync): Warning: I/O leak: 0x414190 (line 102, fd 16) Apr 30 19:44:59 tornado dovecot: dsync-local(cisco): Error: remote: doveadm(cisco): Fatal: User doesn't exist Apr 30 19:44:59 tornado dovecot: dsync-local(cisco): Error: read() from worker server failed: EOF

Users mozsync and cisco are not valid mail users and it's not appropriate that Dovecot tries to create a Maildir for either of them. The users are system unprivileged users only, and do not ever send or receive mail.

And - I/O leak? ;)

Also, user cisco is local to one box only, and does not exist (nor does it need to) on the remote host. So any complaints about this user are invalid and dovecot needs to ignore replication for this user anyway.

Fourth question, upon starting dovecot again, mail.log then spews several hundred of these messages:

Apr 30 19:45:06 tornado dovecot: dsync-local(reuben): Error: msg-get failed: box=Trash uid=114863 guid=1335382569.M98089P29952.tornado,S=6479,W=6625

Before aborting entirely with:

Apr 30 19:45:09 tornado dovecot: imap: Server shutting down. in=328 out=2042

It seems to me that a a few of those problems logged could be solved by being able to specify which system users to synchronise, rather than Dovecot making a blind assumption that all users actually have valid Maildirs that need to be created, and all need to be sync'd between two hosts.

Subsequent delivery based sync'ing fails silently (pending more investigation) but I'd like to try and fix the above listed problems first before worrying about the later stages of the sync not working.

Has anyone else run into these problems or found better ways of making this type of setup all work?

Thanks, Reuben