[gentoo-user] Re: Heads Up - glibc-2.27 breaks my system

[Nikos Chantziaras]

On 03/02/18 07:54, Dale wrote:
> While on this topic, I have a question about glibc.  I have it set in
> make.conf to save the binary packages.  Generally I use it when I need
> to go back shortly after a upgrade, usually Firefox or something.
> However, this package is different since going back a version isn't a
> good idea.  My question tho, what if one does go back a version using
> those saved binary packages?  Has anyone ever did it and it work or did
> it and it fail miserably?

It is perfectly fine to downgrade glibc if you didn't emerge anything 
that compiled binaries.

If you did, you can still downgrade, but then you need to rebuild the 
packages that you emerged since the glibc upgrade. qlop is your friend 
here; it lets you find out the dates on which you emerged packages.

This whole thing is not actually special to glibc. Other libraries work 
in a similar manner. You can't just link other software against a new 
version of the library, then remove the library and replace it with an 
older one. It might result in breakage. But glibc is used by almost 
everything, it's not "just a library", it is *the* library, and so it 
has a special protection to prevent a downgrade. You can bypass that 
protection and downgrade anyway, but then you need to know what you're 
doing and how to restore your system correctly. If any sys-devel 
packages are affected, you might not be able to do it. If only end-user 
packages are affected which are not used during an emerge, then it's 
quite safe to downgrade.