Upgrading Ubuntu advice

Spin up a new linode with 12.04, copy over all your configs, then swap IP's to the new one. Billing is pro-rated to the day, so if you get it done in a day or two, it only costs a couple bucks assuming a 1024 (note that you do pay up front for the month, but you'll get back a credit when you destroy the old one).

I agree with glg, put the "build" step before "destroy" so you're preparing the 12.04 node in parallel with the existing node and only cutting over once everything looks good. Depending on the amount of dynamic state (e.g., databases or data files) you may have some small amount of actual down time while you transfer over the final updates, but it'll be as short as possible (and less risky). You can also run parallel tests to ensure that nothing has broken with all the various packages that may be running later versions.

While I have nodes in a similar state and also plan to migrate by installing 12.04 anew, I wouldn't necessarily discount the in-place upgrade if that might be easier. Though I think you have to do 10.04 first and then 12.04. But a second node is a great test case for that too. Create the node and then clone your current node to it* (or if you have backups enabled, use a snapshot to avoid any down time). Then give the upgrades a shot. Worst case it doesn't work (or is more complicated than you want) and you just go back to starting with a new install and bringing over the configs by hand.

– David

*   Remember to use rescue mode to tweak any external facing tasks or configurations (like host name) that might be inherited from the production node but you don't want running on the second box.</t>

Indeed, you can upgrade directly between LTS releases, but you can't jump over 10.04, that has to be the intermediate step.

Thanks for all your help, folks. I'm going to do both: clone, make modifications to mitigate the cloning, boot the clone and upgrade the clone in place from 8.04 to 10.04 then from 10 to 12. If it all works, I change DNS to point to the upgraded clone and I'm done. If it doesn't, I do the configs by hand, then change DNS then finally hose the old Linode when some backups accrue on the new one.

EDIT: swap IPs is what I actually meant by change DNS.