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shadow-utils 4.8.1


change and administer password and group data


Utilities for managing accounts and shadow password files


Password and account management tool suite with support for shadow files and PAM


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.
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 systems 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:
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.


Group account information.
Secure group account information.
Shadow password suite configuration.
User account information.


The groupmod command exits with the following values:
E_SUCCESS: success
E_USAGE: invalid command syntax
E_BAD_ARG: invalid argument to option
E_GID_IN_USE: specified group doesnt exist
E_NOTFOUND: specified group doesnt exist
E_NAME_IN_USE: group name already in use
E_GRP_UPDATE: cant update group file
E_CLEANUP_SERVICE: cant setup cleanup service
E_PAM_USERNAME: cant determine your username for use with pam
E_PAM_ERROR: pam returned an error, see syslog facility id groupmod for the PAM error message
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