[Mashiro]

@deanhills

Usually apt-get update && apt-get upgrade don't perform major version upgrades of the OS. These two commands refresh the local package database to see whether updates are available and if updates are available the packages affected are then updated to the new available versions.

In order to perform a major upgrade you'd need to do a little more work than these two commands. You need to update the sources in /etc/apt/source.list to the one from the release you want to upgrade to. And then run apt-get update && apt-get dist-upgrade to perform a "distribution upgrade".

There is also another trick that however may not always work as intended. When you update sources.list to the new version and run apt-get update && apt-get upgrade you will be able to simply update your packages to the version from the newer release of Ubuntu without a major distribution upgrade. This may however not always work due to compatibility and it isn't safe! Why? It would also attempt to upgrade some system packages that are vital but this will mostly break during such updates and the whole OS would collapse.

You probably knew that already though .


Long story short: I guess OP was just performing a normal update of packages instead of what you thought could be a distribution upgrade to a higher version. That said distribution upgrades on OpenVZ are possible. I could upgrade Debian 7 to Debian 8 without issues but Debian 8 to Debian 9 unfortunately didn't work 100%. Never tried Ubuntu.