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

[Nikos Chantziaras <realnc@gmail.com>]

On 03/02/18 16:08, Dale wrote:
> Nikos Chantziaras wrote:
>> 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.
> 
> That makes sense.  So, if worse comes to worse, downgrade, then emerge
> -e world if unsure what all has been updated since.  If, using qlop or
> friends, you can figure what was done since the upgrade, emerge those to
> make sure the linking is correct.  At least that is a option that should
> be doable.  That's better than thinking you can't downgrade for any
> reason, period.

You might not be able to do that, if python (used by emerge) uses 
something that breaks when downgrading glibc. Or gcc. Or binutils. Or 
bash. Or anything else that's needed during an emerge.

So you need to check with qlop *before* downgrading, and if it looks 
like something critical was built against the new glibc, then all bets 
are off. Which is why the downgrade protection exists in the first place.

The only way out of this, is restoring from backup or fixing things by 
booting from a sysrescuecd or similar.

If only firefox or your media player and stuff like that got built 
against the new glibc, then it's fine to downgrade. Otherwise, you could 
end up bricking your system.