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List:       gentoo-dev
Subject:    Re: [gentoo-dev] Assigning unique system uid/gid for new ebuild
From:       Evan Powers <powers.161 () osu ! edu>
Date:       2003-05-31 23:43:33
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On Saturday 31 May 2003 04:53 am, Martin Lesser wrote:
> I don't see any benefits of developing and/or maintaining a predefined
> /etc/passwd with more than exactly one entry for root.

I'm quite tempted to agree with you, but one problem does come to mind. Unless 
I'm missing something, it's important enough to prevent such an approach.

Say any one of three things happens:
1) Your computer has problems and you want to move the drive onto a friend's 
system to repair it.
2) You loose / but not /usr, /var, whatever. You reinstall / but keep the 
other undamaged partitions.
3) You get hacked and have to replace /, but certain other filesystems contain 
only data and therefore are safe to keep

The common thread is that you want to mount a filesystem on a system with a 
/etc/passwd different from the one that filesystem was created under.

Unlike applications, the filesystem can't look at /etc/passwd for the UID/GID 
mappings. If the mappings on different machines aren't' the same, you can't 
easily move a drive to another machine and mount it.

If you emerge packages in a different order, the UID/GIDs in the new 
/etc/passwd will be dynamically generated differently, and won't match those 
in the old system. Changes in ebuild interdependencies would cause this to 
happen even if you issue the exact same sequence of emerge commands.

I can see it being a huge practical advantage to know that two installs will 
have the same UID/GID assignments, and therefore that disk drives can be 
moved between them without mismatches.

Evan


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