---
name: "groupmod"
section: "8"
platform: "linux"
package: "shadow"
version: "4.20.0.arch1-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "openbsd"]
url: "https://new.carta.tech/groupmod"
---

# groupmod(8)

modify a group definition on the system

## 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)](/crypt/3.md).

  **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. No SELINUX support.

- **-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)](/chfn/1.md), [**chsh**(1)](/chsh/1.md), [**passwd**(1)](/passwd/1.md), **gpasswd**(8), [**groupadd**(8)](/groupadd/8.md), [**groupdel**(8)](/groupdel/8.md), [**login.defs**(5)](/login.defs/5.md), [**useradd**(8)](/useradd/8.md), [**userdel**(8)](/userdel/8.md), [**usermod**(8)](/usermod/8.md).