Man page 8 : groupmod

groupmod - modify a group definition on the system

groupmod [options] GROUP

The groupmod command modifies the definition of the specified GROUP by modifying the appropriate entry in the group database.

The options which apply to the groupmod command are:

-g, --gid GID
    The group ID of the given GROUP will be changed to GID.

The value of GID must be a non-negative decimal integer. This value must be unique, unless the -o option is used. Values between 0 and 999 are typically reserved for system groups.

Any files that have the old group ID and must continue to belong to GROUP, must have their group ID changed manually.

-h, --help
    Display help message and exit.

-n, --new-name NEW_GROUP
    The name of the group will be changed from GROUP to NEW_GROUP name.

-o, --non-unique
    When used with the -g option, allow to change the group GID to a non-unique value.

-p, --password PASSWORD
    The encrypted password, as returned by crypt(3).

Note: This option is not recommended because the password (or encrypted password) will be visible by users listing the processes.

You should make sure the password respects the system\*(Aqs password policy.

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.

The groupmod command exits with the following values:

0
    success

2
    invalid command syntax

3
    invalid argument to option

4
    specified group doesn\*(Aqt exist

6
    specified group doesn\*(Aqt exist

9
    group name already in use

10
    can\*(Aqt update group file

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