Manpages - groupmems.8

groupmems - administer members of a users primary group

groupmems -a user_name | -d user_name | [-g /group_name/] | -l | -p

The groupmems command allows a user to administer their own group membership list without the requirement of superuser privileges. The groupmems utility is for systems that configure its users to be in their own name sake primary group (i.e., guest / guest).

Only the superuser, as administrator, can use groupmems to alter the memberships of other groups.

The options which apply to the groupmems command are:

-a, –add user_name

Add a user to the group membership list.

If the /etc/gshadow file exist, and the group has no entry in the /etc/gshadow file, a new entry will be created.

-d, –delete user_name

Delete a user from the group membership list.

If the /etc/gshadow file exist, the user will be removed from the list of members and administrators of the group.

If the /etc/gshadow file exist, and the group has no entry in the /etc/gshadow file, a new entry will be created.

-g, –group group_name

The superuser can specify which group membership list to modify.

-h, –help

Display help message and exit.

-l, –list

List the group membership list.

-p, –purge

Purge all users from the group membership list.

If the /etc/gshadow file exist, and the group has no entry in the /etc/gshadow file, a new entry will be created.

-R, –root CHROOT_DIR

Apply changes in the CHROOT_DIR directory and use the configuration files from the CHROOT_DIR directory.

The groupmems executable should be in mode 2710 as user root and in group groups. The system administrator can add users to group groups to allow or disallow them using the groupmems utility to manage their own group membership list.

    	$ groupadd -r groups
    	$ chmod 2710 groupmems
    	$ chown root.groups groupmems
    	$ groupmems -g groups -a gk4
        

The following configuration variables in /etc/login.defs change the behavior of this tool:

MAX_MEMBERS_PER_GROUP (number)

Maximum members per group entry. When the maximum is reached, a new group entry (line) is started in /etc/group (with the same name, same password, and same GID).

The default value is 0, meaning that there are no limits in the number of members in a group.

This feature (split group) permits to limit the length of lines in the group file. This is useful to make sure that lines for NIS groups are not larger than 1024 characters.

If you need to enforce such limit, you can use 25.

Note: split groups may not be supported by all tools (even in the Shadow toolsuite). You should not use this variable unless you really need it.

/etc/group

Group account information.

/etc/gshadow

secure group account information

*chfn*(1), *chsh*(1), *passwd*(1), *groupadd*(8), *groupdel*(8), *useradd*(8), *userdel*(8), *usermod*(8).