More on UIDs

Bruce Dubbs bdubbs at
Thu Apr 21 15:29:18 PDT 2005

Jeremy Utley wrote:
>>In the book, we create a lot of users and groups.  Almost none of them
>>have uids/gids specified.  Right now, if a user/group is created without
>>specifying,  a uid value > 1000 or a gid value > 100 is used.  The LSB
>>says system uids/gids should be below 100.  I am proposing a book wide
>>coordinated set of numbers:
> *snipped*
> Actually, my suggestion would be for those system users that are
> associated with network daemons, to use a group to match the port they
> open...i.e. apache assigned 80, ssh assigned 22, etc.  No real reason,
> except to try to have SOME rhyme/reason to assignment - those that don't
> do network stuff can be assigned somewhat arbitrarily.

Not a bad idea, but we have several ftp and email servers.  I thought
about using the same number for all the ftp servers and the same numbers
of all the mail servers, but that would make the different packages
conflict.  I opted for making the numbers of related apps close
together.  Also it doesn't work for things like pop (110).

It does work for apache, ssh, and named and I can do that.

The implementation I was thinking about is to add a page to Chapter 2 or
Chapter 3 named "About uids and gids" that sumarizes uid/gid issues.  It
should also discuss User Private Groups and mention the interaction and
possible update of /etc/login.defs.

  -- Bruce

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