Corruption & migration

Daniel Miller dmiller at
Tue Mar 21 08:30:02 EET 2017

I'm getting close - I believe I have one-way replication processing 
now.  It's amazing watching the mails magically appear in the new 
server!  I'll tender some updates to the wiki in the hopes it will help 

At this time, I have two errors I haven't been able to eliminate with 
config changes:

dovecot: doveadm: Error: dsync-remote(user at Warning: 
Transaction log file 
was locked for 109 seconds (rotating while syncing)
Mar 20 23:22:04 bubba dovecot: dsync-local(user at Error: 
Remote command returned error 75: ssh -lvmail doveadm 
dsync-server -uuser at

I don't know if the transaction lock issue will fix itself via repeated 
replication runs.  But I have no idea what the "error 75" is.


On 3/20/2017 10:05 PM, Daniel Miller wrote:
> I have an existing server using mdbox & sis. There is a quantity of 
> corruption - I have no idea where it came in.  I'd had a previous 
> rebuild some years ago and I thought I had a clean datastore.  By 
> "corruption" I mean missing attachments and either missing or mixed-up 
> emails.
> I've setup a new server on a virtual machine.  Instead of copying the 
> old configs I hand-adjusted individual settings using the current 
> distribution example.  The new server is running...but empty.
> So now my intent is to migrate the mail to the new machine.  A few 
> items to note:
> 1.  The existing mail server is the virtual host.  The mails are 
> stored locally, in mdbox format, with sis enabled.  And possibly zlib.
> 2.  The new server, via VirtualBox, is presently configured for 
> Maildir.  I may change to sdbox - I'm now a little reserved about mdbox.
> 3.  Instead of storing the mails within the virtual machine, I'm using 
> the host's drive.  This is via an exported NFS4 folder from the host, 
> mounted on the guest, using the options: 
> "auto,noatime,hard,intr,async,nordirplus".
> 4.  My intent is to have the new virtual server become the primary 
> mail server.  The mail store will continue to be accessed by NFS4. No 
> other servers or processes (besides backup) should access the mail store.
> question is what is the best method for the migration?
> Reading the docs on Dovecot replication I'm still very unsure of how 
> to implement it - particularly the "master-master" or "master-client" 
> relationships.  The docs are not 100% clear on which server gets which 
> options.  I can guess...which I'd really rather not do.  But it seems 
> to me getting one-way replication working would be the most "elegant" 
> solution here.
> Manual dsync is also an option - but again I'm not on which machine I 
> should execute which options.
> Imapsync is a possibility and the syntax is clear - but very slow in 
> execution for 100k mails.
> Any suggestions or pointers would be welcome.

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