Re: Migrating maildirs - Courier to Dovecot

On 22 Sep 2017, at 00:15, Adi Pircalabu adi@ddns.com.au wrote:

Using rsync should be fine, I've done it myself recently several times. What you need to consider:

1. The downtime required during the final incremental transfer.
2. If you're using the same uid/gid on the destination server make sure you preserve them when transferring the data across.
3. To avoid duplicate messages in the destination you *must* use --delete rsync switch for the incremental transfers.

Important: I'm assuming you're using virtual mailboxes under the same uid/gid.

Suggested mandatory steps, ymmv:

1. Configure Dovecot in the destination to use Maildir and test everything: logging, SSL, authentication, mail delivery and so on. If you have Courier-IMAP specific configuration, e.g. folders that are being automatically created/subscribed upon the first login, replicate it and test it on the Dovecot server as well.
2. Do the initial data transfer using "-avz --numeric-ids" and see if you're happy with the result in the destination.
3. Run several incrementals adding "--delete" switch, followed by courier-dovecot-migrate.pl *executed as the mail user* to get a ballpark figure for the estimated outage window.
4. Test few mailboxes post-migration and compare the results with the source server.
5. On Day D, stop Courier-IMAP and Dovecot services on both servers to prevent any mailbox changes and run the last incremental, sanity checks, IP reconfiguration if Dovecot is the drop-in replacement, start Dovecot, another round of sanity checks, check the logs and so on. Here you're already at the point of no return :)

This is all more or less as I hoped or planned it, although you have mentioned some details that I will now be sure not to overlook.

Many thanks.

Stroller.