GROUPMEMS

Section: System Management Commands (8)
Updated: 03/29/2021
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NAME

groupmems - administer members of a user's primary group

SYNOPSIS

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

DESCRIPTION

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.

OPTIONS

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.

SETUP

In this operating system the groupmems executable is not setuid and regular users cannot use it to manipulate the membership of their own group.

CONFIGURATION

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.

FILES

/etc/group

: Group account information.

/etc/gshadow

: secure group account information