I would like to upgrade my Ubuntu 18.04.6 LTS (Bionic Beaver) to latest/greatest version because the current one is going to be EOL in May 2023. Any one done this upgrade please provide the steps.
However I tried upgrade my server using below command but it says my current OS is not LTS and I need to try to non-LTS. What is wrong?
sudo do-release-upgrade -d
You should normally not use the -d option with do-release-upgrade.
Let's check the man page:
-d, --devel-release If using the latest supported release, upgrade to the development release
The -d option should only be used when you are on the latest supported release (at this time Ubuntu 23.04), and want to upgrade to the next development release. In addition, the -d option will also be relevant right after the release of a new LTS version (say when Ubuntu 24.04 is released), and you want to upgrade an existing 22.04 version before the first point release (24.04.1) unlocks the LTS upgrade window (usually in August) - but this should be considered an advanced usecase.
Instead, you can use the -c option to check which version you will upgrade to:
-c, --check-dist-upgrade-only Check only if a new distribution release is available and report the result via the exit code
So to verify the upgrade path run:
do-release-upgrade -c
Afterwards, perform a normal upgrade command with no options:
sudo do-release-upgrade
