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I just noticed that the focal-proposed repository was included in my sources.list on ubuntu 20.04, although that doesn't seem to be recommended. After disabling it, the command
apt-show-versions | grep newer
shows around 30 packages whose installed version is newer than the one in the repository. Is there a simple way to downgrade all of them to the available version?
I wrote a similar answer here
To do this, first remove any lines with focal-proposed from /etc/apt/sources.list and /etc/apt/sources.list.d/*.
Second we are going to tell apt to allow downgrades. That means pinning focal, focal-updates and focal-security with priorities higher than 1000. Create /etc/apt/preferences.d/focal with this content:
Package: *
Pin: release n=focal
Pin-Priority: 1001
Package: *
Pin: release n=focal-updates
Pin-Priority: 1002
Package: *
Pin: release n=focal-security
Pin-Priority: 1003
If you don't use focal-updates or focal-security then skip those sections.
Third, run the following:
sudo apt update
sudo apt upgrade
sudo apt dist-upgrade
sudo apt --fix-broken install
sudo apt autoremove
and keep rotating between those commands until everything is stable.
Finally, delete /etc/apt/preferences.d/focal.
Alternatively, you can just delete focal-proposed. Those packages will eventually migrate to focal-updates when they pass their test and you'll be in sync again.
With your small delta, --fix-broken install and autoremove probably won't be neccessary but apt will tell you when you read the output of the previous commands.
To anyone else who comes accross this post: Downgrading is not supported. Any downgrade of significant size is likely to fail. This is a pretty trivial case, but going from focal to bionic would probably be a disaster and leave you with a broken system.
man apt_preferences describes o= as the "originator of the packages in the directory tree of the Release file". I don't honestly know what that means other than the given example is Debian. n= is the codename (bullseye, bionic, or focal-updates). a= is the suite (stable, unstable, testing)
Pin: release o=Debian Pin-Priority: -10 will uninstall any packages which are not Debian-originated.
release o=* constraint means "not locally installed", that is, packages which have a known origin. If your sources contain only the repos from which you want package version installed, it's a shorter than spelling out specific names.
Oct 29, 2020 at 9:31
Little bit shorter.
cat /etc/apt/preferences.d/focal.pref
Package: *
Pin: release n=focal
Pin-Priority: 1001
The record assigns a high priority to all package versions belonging to any distribution whose Codename is "focal".
Note works only when focal-proposed is no longer active.
