Updating a Debian VM 5.0.10 to 6 on a XenServer (5.6.0)

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I'm about to update an old but production Debian Lenny 5.0.10 box to Debian 6 Squeeze.
It is a VM running on a XenServer.

(I do have a "snapshot" of the 5.0.10 box, so going back should be easy when needed.)

Anyone here who might have some tips on what to do and what not.

Thank you.

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I've updated the server with no problem after using the small howto that was posted by Kristian Eklund in http://forums.citrix.com/thread.jspa?threadID=282000

MySQL did not start after the update, however removing skip-dbd from /etc/mysql/my.cnf fixed it.