is it possible to have a 1000 user in single group

UNIX for Advanced & Expert Users
1

I m usi ng RHEL 4 and /etc/group file contains line 7000 characters.
so it is possible to have a 1000 user in single group

2

I'm not sure what you are asking - /etc/group is supposed to be limited to LINE_MAX bytes per line. So LINE_MAX bytes can be used to describe users in the group. Check your man page.

getconf LINE_MAX

shows your system's value for this.

The record layout is:

group_name:passwd:GID:user_list

where user_list is a comma delimited list of user names in the group.

Where does 1000 come in? LINE_MAX and username length (plus a comma) are the limiting factors. 7000 bytes in a line and 5 character usernames (if allowed) will give 1000+.

3

There is no limit on the number of users in a primary group. The limit of LINE_MAX applies to each secondary group. It is not necessary or advisible to list any users primary group in /etc/group .
Though not tried on Red Hat, I have seen multiple lines for the same group in /etc/group in a very large unix SVR4 system.

4

I have seen the same thing:
realgrp::123:user1,user2
dummy1::123:user3,user4
dummy2::123:user5,user6

All six users are in group 123. And when group 123 is translated, it comes out as "realgrp".

5

We are adding 1000 users having secondary group. After adding 1000 users, Line of secondary group contains 7053 characters.

Is there any way to change LINE_MAX value of OS ???
Currently LINE_MAX value is 2048.

Thanks in advance...

6

You don't need the dummy group names.
You can have multiple lines for the same group.