Re: How did I get into dependency hell and how do I get out?

[Greg Wooledge <greg@wooledge.org>]

On Fri, Jul 15, 2022 at 12:08:12PM -0400, Dan Ritter wrote:
> Ottavio Caruso wrote: 
> > $ apt-cache policy libglib2.0-0
> > libglib2.0-0:
> >   Installed: 2.72.1-1
> >   Candidate: 2.72.1-1
> >   Version table:
> >  *** 2.72.1-1 100
> >         100 /var/lib/dpkg/status
> >      2.66.8-1 500
> >         500 https://deb.debian.org/debian bullseye/main amd64 Packages
> 
> That's a version from later-than-bullseye.

Not only that, but it's also a version that's no longer present in any
of Ottavio's sources.

So, what I'm concluding is that Ottavio did something like this:

1) Decided to try installing some packages from testing or unstable.

2) Added testing or unstable to sources.list.

3) Installed stuff from testing or unstable.  At least libglib2.0-0.

4) Removed testing or unstable from sources, thinking that this would
   let them keep a "stable system except for these few packages".

This is what we call a Frankendebian.

Once you've installed packages from testing or unstable, there is no
going back.  There is only going forward.  You can continue "upgrading"
the rest of the system to testing or unstable (whichever you chose),
or you can reinstall everything using only stable sources.

(Is that a 100% firm rule?  No, of course not.  There are certain packages,
at certain moments in history, that can be downgraded to a stable version,
or removed, or which can peacefully coexist with a stable system, despite
being from a different release.  But it takes an expert to identify such
a unicorn.)