Upgrading Ubuntu 10.04 to 12.04 - Anything to look out for?

I upgraded a while back, and the biggest (only?) issue I ran into was php-fpm looking for the pool configuration files in a different place. That was somewhat expected though, since the php-fpm I was using on 10.04 was from a ppa. logwatch seems to be a bit different too, but I haven't really been motivated to look into it since it's still giving me the information I need.

Can't help you with the specific upgrade, but some generic advice: if you want to avoid downtime, you're better off doing the following. Get a new Linode the same size as your current one in the same datacenter, and clone the existing Linode. Perform the upgrade on the new Linode and fool with it until everything's working the way you want. Shut down external-facing services on the old Linode and copy over to the new one any changes in data since the clone was made (usually database files, but also mail and uploads, if you allow those). Switch the IPs between the two Linodes.

Now your new Linode will be running 12.04 and acting as your server. Once you're satisfied everything is OK, remove the old Linode. You'll be billed a little extra since you'll be running two Linodes instead of one for a day or two, but since charges are prorated it's not much of an expense.

The backup, upgrade, restore-if-a-problem-occurs method also works, but at the risk of more downtime.

Thanks. It worked perfectly.