Cyrus upgrade from 2.1.18 to 2.2.13 moved email messages

[Steinar Bang]

Final words on the upgrade: Moving the mailboxes in the
/var/spool/mail/ gave something that couldn't be opened.

Running
	/usr/sbin/cyrreconstruct -r user.*

on /var/spool/mail/ gave me openable mailboxes, but the read marks were
gone (probably the .seen databases took an early beating in this
process.  I made a backup, but probably not early enough).

Losing the seen marks is something I'm used to.  It happened when I
transitioned from 1.5.x to 2.1.x back in 2002, and has happened two or
three times during my 2.1 days (which eventually led me to convert from
BDB to skiplists, and I haven't had any problems with it upp until now).

Soooo... I'll bite the bullet like I did the other times and reconstruct
the .seen marks, as near as I can.  Come tuesday my email server has
been out of service for a week.

The lesson for next upgrade (that is not a 2.2.x upgrade, which I let
apt-get deal with), is to make a complete copy of /var/lib/cyrus and
/var/spool/cyrus before even Starting (USB HDs are cheap these days...),
and then to convert mailboxes.db and the .seen databases to flat text
files before uninstalling the previous version (are there others I need
to transfer?).  This is just a precaution.  With all significant
databases as skiplists, I don't think this step is neccessary anymore.
But it doesn't hurt to make sure.