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Linux and Unix groupmod command

groupmod commandAbout groupmod
groupmod syntax
groupmod examples
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About groupmod

Enables a superuser or root to modify a group.

Description

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

groupmod syntax

groupmod [options] GROUP

Options

-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.

-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.

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. See also chroot.

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.

Exit Values

The groupmod command exits with the following values:

0

success

2

invalid command syntax

3

invalid argument to option

4

specified group doesn't exist

6

specified group doesn't exist

9

group name already in use

10

can't update group file

groupmod examples

Tip: For this command to work you must have superuser rights or be logged in as root.

groupmod -n bettergroup newgroup

In the above example the groupmod command would change the group "newgroup" to "bettergroup".

gpasswd — Administer /etc/group and /etc/gshadow.
groupadd — Add a group to the system.
groupdel — Remove a group from the system.