I’ve had my Plex Media Server running on Ubuntu 12.04 on XS 6.2 for a while now. It recently started nagging me to upgrade to 14.04. Didn’t see a reason not to do this, but I also didn’t do much digging to see if there were known issues. Turns out, 14.04 is not a “supported” version on XS 6.2. The updated image refused to boot. It ended up being a pretty simple fix of going into the XS host and modifying a Grub configuration file. It was an easy thing to find through googling. First item in the results.
I should also mention, the Ubuntu Dist Upgrade also uninstalled Plex. That was an easy fix, but it did require a reboot for Plex to start working.