modify a group definition on the system


Change the group name

$ groupmod -n [new_group_name] [old_group_name]

Change the group id

$ groupmod -g [new_group_id] [old_group_name]


' groupmod 'u 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 .
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 (Aqs password policy .

-R , --root CHROOT_DIR Apply changes in the CHROOT_DIR directory and use the configuration files from the CHROOT_DIR directory .

-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 .


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 .

/etc/login .defs Shadow password suite configuration .

/etc/passwd User account information .


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: specified group doesn (Aqt exist

6 E_NOTFOUND: specified group doesn (Aqt exist

9 E_NAME_IN_USE: group name already in use

10 E_GRP_UPDATE: can (Aqt update group file

11 E_CLEANUP_SERVICE: can (Aqt setup cleanup service

12 E_PAM_USERNAME: can (Aqt 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


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

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