I've been tasked to upgrade an Ubuntu Server 11.04 box to one of the later versions due to support for the Natty end of life being reached last year. I've no idea how they got by for almost 12 months without noticing that the repositories don't fully work anymore but that's besides the point..
My initial thought was a clean rebuild from 12.04 or 12.10 and then build the services on top, but I'm told that downtime of the server should be kept at a minimum. To that end I'm looking at an in-place upgrade from 11.04 to 12.04/12.10.
I understand that Ubuntu upgrades should be 'staggered' - ie 11.04 > 11.10 > 12.04 > 12.10 - but I'm quite wary about performing this in-place. I'm happy to do it in stages, verifying all services and processes start and perform with each stage of the upgrade, but it just seems like an ill-advised idea to me. I may be wrong but how can I guarantee that services will stay stable through the course of the upgrade?
What are you thoughts and experiences? I'd be really appreciative of any advice or pointers you have. Thanks in advance.