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[Debian system] tuning number of groups for a user


It is a question of increasing the number of groups to which
a Linux user can belong.
By default, this number is 32 (cf /usr/include/linux/limits.h or
in the sources of the kernel /usr/src/linux/include/linux/limits.h).
The distribution is Debian 2.2 (potato), the kernel is the 2.2.19.

By modifying the following line in these headers:
# define NGROUPS_MAX 32
# define NGROUPS_MAX 64
and by compiling the kernel, this one must be able to support
the increase. One needs then recompile some packages:
- shellutils
- login
- passwd
which contain the utilities for managing users and groups.
After their installation, some problems remains: usermod works
correctly and wants to make well belong a user in 64 groups,
but id returns only the first 32 groups to which belongs
the user. IMO, the sources of id do not seem in question.

The goal of the operation is to increase the number of
VirtualHosts managed by Apache (a VHost = a User/Group couple).
In detail:
- Apache is started by a user (for Debian, www-data);
- scripts PHP are also started by this user;
- to preserve each VHost environment, only user and his/her group
can go the base directory;
- So that scripts PHP are executed correctly in the environment
of each VHost, it is necessary that the user www-data belongs
to the user group who possess each VHost.

So, here are beginning my problems...

Do I need to recompile Apache?
If someone has an idea or eventually another solution?
How is it managed on ISP servers?

Best regards.
¤ Stéphane Le Béchennec ¤ ENIC Telecom Lille 1 - Promotion TTN03 ¤

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