Upgrade path from 16.04 to 20.04 LTS without GUI change

Solution 1:

First, if you're looking for stability, then you must wait till June for the first point release of 20.04.

Second, you cannot upgrade 16.04 directly to 20.04. You first need to reach 18.04 and then 20.04. Amid this, you'll definitely lose Unity as 18.04 uses GNOME. But, guess what you can also customize your Ubuntu replacing GNOME with Unity later on.

Lastly, without GUI? Yes, you can use the single-line command for upgradation:

sudo apt update && sudo apt upgrade

sudo do-release-upgrade

You can also configure it for checking any new release version, in case it is configured for checking only LTS release. For the same, update the file:

sudo vim /etc/update-manager/release-upgrades

Change 'Prompt=normal' or 'Prompt=lts'

If you're not able to get Ubuntu 20.04, use development version using the command:

sudo do-release-upgrade -d 

Solution 2:

I had the problem that sudo apt update failed and thus I was not able to proceed to do-release-upgrade ( I got stuck on Please install all available updates for your release before upgrading..)

I was able to fix most problem using the suggestion provided here and removing some packages (in my case skypeforlinux).

Later I also encountered the problem that there was apparently a problem with the symlink to python3 , while the fix was indeed fixing the symlink for python via sudo ln -sf /usr/bin/python2.7 /usr/bin/python.