groupmod command

Modify a group definition on the system.

Overview

The groupmod command is used to modify the attributes of an existing group on a Unix/Linux system. It can change a group's name (GID) or numeric ID (GID), allowing administrators to manage group accounts efficiently.

Options

-g, --gid GID

Change the group ID to the specified value.

$ sudo groupmod -g 1001 developers

-n, --new-name NEW_GROUP

Change the name of the group from GROUP to NEW_GROUP.

$ sudo groupmod -n engineering developers

-o, --non-unique

Allow using a non-unique GID (normally GIDs must be unique).

$ sudo groupmod -g 1001 -o marketing

-p, --password PASSWORD

Change the password for the group to the encrypted PASSWORD.

$ sudo groupmod -p encrypted_password developers

-R, --root CHROOT_DIR

Apply changes in the CHROOT_DIR directory and use the configuration files from the CHROOT_DIR directory.

$ sudo groupmod -R /mnt/system -n engineering developers

Usage Examples

Changing a group's name

$ sudo groupmod -n developers programmers

Changing a group's GID

$ sudo groupmod -g 2000 developers

Changing both name and GID

$ sudo groupmod -g 2000 -n engineering developers

Tips:

Verify Group Changes

After modifying a group, use the getent group command to verify the changes:

$ getent group engineering

Consider File Ownership

When changing a group's GID, files owned by the old GID won't automatically be updated. Use find and chgrp to update file ownerships:

$ find /path/to/directory -group old_gid -exec chgrp new_gid {} \;

Check for Running Processes

Before modifying a group that's used by running processes, check if any processes are using it:

$ ps -eo group | grep groupname

Frequently Asked Questions

Q1. Can I change a group's name and GID at the same time?

A. Yes, you can use both the -n and -g options together in a single command.

Q2. What happens to files owned by a group if I change its GID?

A. Files will still reference the old GID number. You'll need to manually update file ownerships using chgrp or similar commands.

Q3. Can I make a group's GID the same as another group's?

A. Yes, but only if you use the -o (non-unique) option. However, this is generally not recommended as it can cause confusion.

Q4. Will changing a group's name affect users who are members of that group?

A. No, changing a group's name doesn't affect its membership. Users who were members of the old group name will automatically be members of the new group name.

References

https://man7.org/linux/man-pages/man8/groupmod.8.html

Revisions