dovecot - Jul 2018 - best practices for migrating to new dovecot version

I have a machine with my mail service on it running Debian Squeeze.  The
version of dovecot on that server is 1.2.15.

I'm building a new server with Ubuntu 18.04 (started with 16.04,
upgraded in place), where the dovecot version is 2.2.33.  I plan to
migrate all my services to this new machine.

The virtual mailboxes are on disk in maildir format, with accounts in a
mysql database managed by postfixadmin.  When I copy them over to the
new machine, would there be any value to excluding the files that
dovecot creates, and letting the new version recreate them?  In one
mailbox here are some of the files I am considering excluding:

dovecot.index
dovecot.index.cache
dovecot.index.log
dovecot.index.thread
dovecot-keywords
dovecot-uidlist
dovecot-uidvalidity
dovecot-uidvalidity.5876ca77

There are other files under consideration, like maildirsize and
maildirfolder.  One that I would be sure to *not* remove is subscriptions.

If there are recommendations about dovecot files in a maildir that
should not be removed during a migration, please let me know.

I'm aware that rebuilding this information could be slow.  My own
personal mailbox on the system is over 8GB in size and has well over
nine hundred thousand files in it.

Thanks,
Shawn

Hi,

> On 17 July 2018 at 22:01 Shawn Heisey <elyograg at elyograg.org>
wrote:
> 
> 
> I have a machine with my mail service on it running Debian Squeeze.  The
> version of dovecot on that server is 1.2.15.
> 
> I'm building a new server with Ubuntu 18.04 (started with 16.04,
> upgraded in place), where the dovecot version is 2.2.33.  I plan to
> migrate all my services to this new machine.
> 
> The virtual mailboxes are on disk in maildir format, with accounts in a
> mysql database managed by postfixadmin.  When I copy them over to the
> new machine, would there be any value to excluding the files that
> dovecot creates, and letting the new version recreate them?  In one
> mailbox here are some of the files I am considering excluding:
> 
you can probably ignore these.
> dovecot.index
> dovecot.index.cache
> dovecot.index.log
> dovecot.index.thread
do not ignore these
> dovecot-keywords
> dovecot-uidlist
> dovecot-uidvalidity
> dovecot-uidvalidity.5876ca77
> 

> There are other files under consideration, like maildirsize and
> maildirfolder.  One that I would be sure to *not* remove is subscriptions.
> 
> If there are recommendations about dovecot files in a maildir that
> should not be removed during a migration, please let me know.
> 
> I'm aware that rebuilding this information could be slow.  My own
> personal mailbox on the system is over 8GB in size and has well over
> nine hundred thousand files in it.
> 
You can just rsync everything over to new system.
> Thanks,
> Shawn

On 7/17/2018 1:16 PM, Aki Tuomi wrote:
> You can just rsync everything over to new system.
I did a few initial rsyncs some time ago.  So a new rsync will be
relatively quick.  There's 25GB of data and over a million files in the
copy on the new server, which is probably a few months out of date
compared to the online server.  The online machine is very slow and I
hate asking it to calculate anything, so I don't know how much data is
left to sync.

If the recommendation is to rsync everything and not exclude certain
files, then I would like to ensure that dovecot rebuilds as much of its
data as I can.  Are there some doveadm commands I should run on the new
server after the rsync and before I bring it fully online?  I am OK with
having a few hours of downtime if it would help dovecot make sure things
are really clean.

At this time, I have not deployed Solr as the search engine for dovecot,
but as I am heavily involved with that community, I probably should. If
there are any guides about switching an existing setup over to Solr,
please point me at them.

Thanks,
Shawn