[Pkg-shadow-devel] The way UIDs and GIDs are created

Martin Bammer mrbm74 at gmail.com
Mon Sep 19 21:08:54 UTC 2016


I've got a suggestion for an alternative UID and GID generation algorithm.
Currently UIDs and GIDs are generated in a way so that the next free one is
chosen when a new user or group is generated.
This leads to problems in small networks with unmanaged users which is the
normal case in home networks.
For users it is very confusing when they share files via Linux/Unix file
systems and these files seem to be owned by different users depending on
the machine where the files are listed.
Wouldn't it be a good idea to have an option to generate UIDs and GIDs by
calculating a hash value?
I know this method is not 100% perfect because at least on Linux currently
only 32bit (or on some systems 31bit) are used for this metadata and there
is a chance to have collisions. But for small home networks with unmanaged
users this method would work most of the time and if there is a collision
the user can be informed about it that an alternative value was chosen.
This method would bring the advantage that users and groups with the same
names usually have the same UIDs/GIDs across all the machines independent
of the order the users were created.
NFS ID-mapping would also usually be not needed.
So what do you think?

Best regards,

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