Backing up of a group of users mailboxes

[Simon Matter]

> Hi,
>
> What is the correct way to backup a couple of users'
> mailboxes?  Those users are leaving the company, but
> I'd like to backup their emails for at least a year to
> a DVD.
>
> I've read somewhere before that Cyrus is not storing
> the email in the users' mailbox IF there are a few
> recipient in the system.  i.e. only store one copy,
> and the rest is linked to that copy.  If that is the
> case, then I can't just do a tar of the users'
> mailboxes?

If you have configured single instance store, Cyrus will hardlink those
files. Now when you backup using tar, the tar program will include the
files correctly. IIRC the only thing which doesn't work is partial extract
of tar files which inlude hardlinks (at least that's the case with GNU
tar). In that case it may happen that you extract a hardlinked file from
the tar and it complains that the target file doesn't exist - of course
because the hardlinked files are also only stored once in the tar and you
didn't extract it with your partial extract.
We don't enable single instance store on servers which are backup up using
Veritas Netback for example, because it uses GNU tar internally and we
always had problems restoring single mailboxes from a full backup because
some of the hardlinked files did not exist anymore at the time of the
restore.
I was always womndering how other people using single instance store deal
with it.
Please note that hardlinks and those problems are not Cyrus specific,
every Linux/Unix system has lot's of hardlinked files in /usr and other
locations and partial restores have always been considered somehow
dangerous.

Simon