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Subject: Re: [gentoo-dev] Requirements for UID/GID management
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From: Michael Orlitzky <mjo@gentoo.org>
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Date: Sat, 28 Jan 2017 21:54:16 -0500
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On 01/28/2017 09:22 PM, Rich Freeman wrote:
> 
> Honestly, I really will say "so what" here.  :)
> 

I forgot to mention a few of the advantages of having really-fixed UIDs.
First, it makes the code simpler. Yup, cool.

It also lets us play a nice trick and use the UID as a subslot, so that
if some sys-user/foo package ever changes its UID, everything depending
on it can be rebuilt to use the new UID.

Finally, it makes the installed image deterministic. Right now to
prevent file collisions, we have to read stuff from /etc/passwd in order
to generate a file that gets installed to /var/lib. The installed image
of a package shouldn't change on-the-fly like that, and it wouldn't if
the UID was truly fixed.

We don't get any of those benefits if we're falling back to random UIDs.