Upgrading Cyrus IMAPd from version 2.1 to 2.2

Upgrading Cyrus IMAPd on a sarge box can be little delightful. In this case the installed version is 2.1.18-1+sarge2, i.e. the last one distributed in sarge. The plan is to upgrade to version 2.2 that is distributed via sarge-backports.

The Debian maintainer thankfully documented most steps required to upgrade form version 2.1 to version 2.2 which includes a move from Berkeley DB 3.2 to Berkeley DB 4.3. The plan includes to convert deliver.db and mailboxes.db with the inhouse utility cvt_cyrusdb. However, the proposed command

   /usr/sbin/cvt_cyrusdb /var/lib/cyrus/mailboxes.db db3 /var/lib/cyrus/temp.db flat

  fatal error: unknown old backend

only results in the error message above. This way no upgrade to the new version is possible. Upgrading the DB file with the command db4.3_upgrade doesn't work either. As mentioned the file tls_sessions.db is not important and thus can be removed and reconstructed automatically.

The other file deliver.db can be treated the same as it only contains message ids of received mails. Thus, a removed database will only result in potentially duplicated mail for the users. In many cases this is acceptable if that's the price for the upgrade.

The third file, however, mailboxes.db must not be deleted. It contains the names of all mailboxes Cyrus maintains including new folders the users have created. Quite important information, it seems.

Since converting the DB files to the new format doesn't seem to be possible in an easy way the file has to be regenerated from scratch. Trashing it and re-creating all mailboxes by hand with the cyradm utility may work for systems with only very few mailboxes, but is not possible for large sites.

Fortunately, cyrus comes with a utility that can dump and restore the mailbox file. The ctl_mboxlist command must be run from the Cyrus user and dumps the database with the switch -d. The resulting text file is used as input for the program after the upgrade using the -u switch.

  /usr/sbin/ctl_mboxlist -d > /tmp/mailboxes.txt

  [upgrade from 2.1 to 2.2]

  /usr/sbin/ctl_mboxlist -u < /tmp/mailboxes.txt

Afterwards Cyrus starts again and the IMAP daemon is up and running again.