groupmod - modify a group definition on the system

       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.

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

       The groupmod command exits with the following values:

       0
           E_SUCCESS: success

       2
           E_USAGE: invalid command syntax

       3
           E_BAD_ARG: invalid argument to option

       4
           E_GID_IN_USE: group id already in use

       6
           E_NOTFOUND: specified group doesn't exist

       9
           E_NAME_IN_USE: group name already in use

       10
           E_GRP_UPDATE: can't update group file

       11
           E_CLEANUP_SERVICE: can't setup cleanup service

       12
           E_PAM_USERNAME: can't determine your username for use with pam

       13
           E_PAM_ERROR: pam returned an error, see syslog facility id groupmod for the PAM error message

/etc/group
           Group account information.

       /etc/gshadow
           Secure group account information.

       /etc/login.defs
           Shadow password suite configuration.

       /etc/passwd
           User account information.

       groupmod - modify a group definition on the system

       The options which apply to the groupmod command are:

       -a, --append
           If group members are specified with -U, append them to the existing member list, rather than
           replacing it.

       -g, --gidGID
           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.

           Users who use the group as primary group will be updated to keep the group as their primary group.

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

           No checks will be performed with regard to the GID_MIN, GID_MAX, SYS_GID_MIN, or SYS_GID_MAX from
           /etc/login.defs.

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

       -n, --new-nameNEW_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, --passwordPASSWORD
           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's password policy.

       -R, --rootCHROOT_DIR
           Apply changes in the CHROOT_DIR directory and use the configuration files from the CHROOT_DIR
           directory. Only absolute paths are supported.

       -P, --prefixPREFIX_DIR
           Apply changes in the PREFIX_DIR directory and use the configuration files from the PREFIX_DIR
           directory. This option does not chroot and is intended for preparing a cross-compilation target. Some
           limitations: NIS and LDAP users/groups are not verified. PAM authentication is using the host files.
           No SELINUX support.

       -U, --users
           A comma-separated list of usernames to add as members of the group.

           The default behavior (if the -g and -U options are not specified) is defined by the USERGROUPS_ENAB
           variable in /etc/login.defs.

chfn(1), chsh(1), passwd(1), gpasswd(8), groupadd(8), groupdel(8), login.defs(5), useradd(8), userdel(8),
       usermod(8).

shadow-utils 4.17.4                                05/07/2025                                        GROUPMOD(8)

groupmod [options] GROUP