Do release upgrade

2022-01-25 linux ubuntu

This is just a memo when I failed to upgrade Ubuntu(from 18 to 20).

$ sudo apt upgrade -y
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Calculating upgrade... Done
The following packages have been kept back:
  libmysqlclient-dev libmysqlclient20 libssl1.0-dev libssl1.0.0
0 upgraded, 0 newly installed, 0 to remove and 4 not upgraded.
$ do-release-upgrade
Checking for a new Ubuntu release
Please install all available updates for your release before upgrading.