Re: Mapping of RIDs to uid_t and gid_t

David Collier-Brown (davecb@Canada.Sun.COM)
Fri, 03 Apr 1998 07:56:49 -0500

Date:	Fri, 03 Apr 1998 07:56:49 -0500
From:	David Collier-Brown <davecb@Canada.Sun.COM>
To:	Jeremy Allison <jallison@whistle.com>
Subject: Re: Mapping of RIDs to uid_t and gid_t

Jean-Francois Micouleau wrote:
> I'm still not convince by this idea. I know several sites (like where I
> worked in a previous life) where the uid are allocated in blocks to make
> some delegations to other sysadmin.

This block-allocation is very common at at least
York University and several large commercial sites,
so groups can cooperate on generating unique userids.
This means that the high 4 bits can be taken (although
most people avoid setting bit 31 (:-))

Therefor ((uid+1000) & 28bits) may cause loss of
significant digits. **May**! It's probabilistic...

Are the group and machine ID's randomly distributed, or are
they individually counted up from 0? I'm having a half-baked
thought (;-))

--dave

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