Gnome control center crashes

[Ralf Mardorf]

On Fri, 04 Oct 2019 00:32:17 +0200, Volker Wysk wrote:
>But it should be possible to revert to the official version, which is
>in the standard repositories, isn't it? The version which got replaced
>by the one from that PPA.

Hi,

the command recommended by Colin is seemingly doing this, see
http://manpages.ubuntu.com/manpages/bionic/man1/ppa-purge.1.html .

It is replacing packages from the PPA with packages from official
repositories, if those packages are provided by official repositories.

If you replace a core component such as libglib2.0-0 from the PPA with
the package from official repositories, resolving dependencies could
become tricky. I could imagine possible dependency cycles, OTOH I don't
know how exactly apt works.

Probably the script (or apt) tries to resolve dependency cycles, but
might fail to do so in some cases. I don't know. I could imagine that
it does replace a lot of packages, but it might not always be possible
to resolve everything in by the first step, so additional steps might
be to run "apt install --fix-broken" and/or "dpkg --configure -a".

Keep in mind that some packages provided by a PPA might either be
provided by another package name, than provided by the official
repositories or it might not be provided at all by official
repositories. IOW it depends on the content of the PPA if everything
can be fixed automatically. In the end it should be possible to fix the
install in a way, that it becomes an official Ubuntu install, but
perhaps is missing packages provided by a PPA, that aren't available by
official repositories.

_Warning!_ Some software configurations and/or data might not be
backwards compatible. After running upgraded software it could migrate
configurations and/or data from an old, to a new format, but downgraded
software can't convert configs and/or data from a new to an old format.

I suspect that you won't suffer from a new vs old data/configure format
issue in $HOME, but you might lose some individual configurations by
purging packages in /etc/, so you might need to backup those configs
and to restore them. Since I never used ppa-purge and I never have
taken a look at the script, it's all guessing.

Regards,
Ralf