How to upgrade EOL (End of life) Ubuntu?

Normally, you can directly do-release-upgrade. But if you try to upgrade EOL system by more than one version, an error may occur: An upgrade from ‘groovy’ to ‘impish’ is not supported with this tool`.

To fix this, try upgrading to a specific version manually:

1. download dist-upgrader from http://archive.ubuntu.com/ubuntu/dists/eoan-updates/main/dist-upgrader-all/current/
2. use hirsute as an example:
   1. tar -xvzf hirsute.tar.gz -C hirsute_upgrade
   2. cd hirsute_upgrade
   3. ./hirsute
   4. sudo apt update
   5. sudo apt upgrade
   6. sudo apt dist-upgrade

However, if your python packages are broken, then another error may occur:
Your python3 install is corrupted. Please fix the '/usr/bin/python3'

Like me, I mistakenly deleted system default python executable , and installed another version with some ugly tricks to keep the system running.

Fortunately, I found another simple solution to upgrade systems.

1. edit source.list to match the next version system ( like 20.10 -> 21.04)
2. sudo apt update
3. sudo apt upgrade
4. sudo apt dist-upgrade

I don’t why, but it just worked…

ref:

1. https://help.ubuntu.com/community/EOLUpgrades/
2. https://butlerraines.com/code-stuff/upgrading-end-life-eol-ubuntu-version-ubuntu-1904
3. https://askubuntu.com/questions/1260939/cannot-upgrade-from-disco-19-04-to-focal-20-04-after-end-of-life-using-do-releas