When upgrading Ubuntu command line, many people probably still change the release name in the sources.list and update && dist-upgrade. Although is still works fine, Ubuntu also provides extras on this front.

Upgrade the new way:

sudo do-release-upgrade

Whats the benefit? It provides things like a temporary SSH server and probably does other sanity checks to increase the chances of an successful upgrade and eases the troubleshooting if things go wrong. The script automatically starts in a screen, so if you get disconnected you resume your upgrade without it being interrupted at all.

The package that manages all this is update-core-manager and you can config for e.g. lts release in /etc/update-manager/release-upgrades.