Ubuntu notes
As of 2025 Q2 Ubuntu server dist upgrades require a package which is not installed in minimal Ubuntu install processes. To install the automating distribution upgrader (note 1):
$ sudo apt install ubuntu-release-upgrader-core
To start the distribution upgrade:
$ sudo do-release-upgrade
When disk space is too small on a partition . . .
$ du -s * | sort -nr | head -n10
To safely remove an old kernel image and related files from /boot . . .
TODO [ ] put at least one note here about cleaning up /boot. Note also that 1024MB while only about 60% full was too full for a long overdue distribution upgrade for an Ubuntu 1804 LTS host. Would be safer going forward to specify a /boot partition size of at least 2 GB or 4 GB. Seems oddly big, may not be necessary in many Linux configurations, but Linode's default Ubuntu image from cerca 2016 did not allow for partition sizing.
When dist-upgrading over ssh:
Reading cache Checking package manager Continue running under SSH? This session appears to be running under ssh. It is not recommended to perform a upgrade over ssh currently because in case of failure it is harder to recover. If you continue, an additional ssh daemon will be started at port '1022'. Do you want to continue? Continue [yN] y Starting additional sshd To make recovery in case of failure easier, an additional sshd will be started on port '1022'. If anything goes wrong with the running ssh you can still connect to the additional one. If you run a firewall, you may need to temporarily open this port. As this is potentially dangerous it's not done automatically. You can open the port with e.g.: 'iptables -I INPUT -p tcp --dport 1022 -j ACCEPT' To continue please press [ENTER]
Dist upgrade 1804 to 2004
After a dist-upgrade from 18.04 LTS to 20.04 LTS may be necessary to reconfigure some elements of apache2 webserver, and may be necessary to uninstall nginx web server. Some elements needing help to bring apache2 back up:
$ sudo apt install libapache2-mod-php7.4
$ sudo a2dismod php7.2 $ sudo a2enmod php7.4 $ sudo systemctl restart apache2
Notes
(1) https://www.cyberciti.biz/faq/ubuntu-bash-do-release-upgrade-command-not-found/