Manual: groupmod

GROUPMOD(8)				 System Management Commands				 GROUPMOD(8)

NAME
       groupmod - modify a group definition on the system

SYNOPSIS

       groupmod [options] GROUP

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

OPTIONS
       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, --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.

	   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-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's password policy.

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

       -P, --prefix PREFIX_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.

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.

       /etc/login.defs
	   Shadow password suite configuration.

       /etc/passwd
	   User account information.

EXIT VALUES
       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

SEE ALSO
       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				 02/02/2026					 GROUPMOD(8)