What is the addgroup command?

It is a command in Linux to create a new group using specified command lined and the system’s default values.

How to add groups

Adding a user group: If we want to add a user group, we either call adduser with the –group option without using the –system option, or we call addgroup.
Adding a system group: To add a system group, we call addgroup with the –system option. Here also, the group created will have no users.
Adding an existing user to a group that already exists: If the adduser is run with two non-option arguments, then the user is added to a group if it already exists.

Syntax:

adduser [--system] [--home DIR] [--shell SHELL] [--no-create-home]
        [--uid ID] [--firstuid ID] [--lastuid ID]
        [--ingroup GROUP | --gid ID] [--disabled-password]
        [--disabled-login] [--gecos GECOS] [--add_extra_groups]
        [--encrypt-home] [--quiet] [--debug] [--force-badname]
        [--help|-h] [--version] [--conf FILE] user


addgroup [--system] [--quiet] [--debug] [--force-badname] [--help|-h]
         [--version] [--conf FILE] [--gid ID] group
adduser [options] usergroup

Some options used in the above line code are explained here:

--conf FILE	This option use FILE in place of /etc/adduser/conf.
--disabled-login	This option makes the user set a password for his account, or else he would not be able to use his account.
--disabled password	This option is similar to –disabled-login, but the user can log in to his account without using a password.
--force-badname	The user and group names are checked, by default. So, this option pressures adduser and addgroup to check roughly for the cogency of the name.
--gecos GECOS	This option will restrict the adduser to ask for finger information.
--gid ID	When this option is used, the given number is forced to bethe new group ID. If a user is created/added, due to this option he is added to that group.
--group	If we want to create the group with the same name as the system user, we combine this option with the --system. If this option is not combined with the --system, then the group with the given name is created.
--help	This option is used to show a help message and exit.
--home DIR	If we use DIR as the user’s home directory, then if the directory does not exist, it is created and the skeleton files are copied.
--quiet	This option only displays errors and warnings and hides informational messages.
--system	This option creates a system group or system user.
--add_extra_groups	This option adds a new user to extra groups.
--version	This option shows copyright information and version.

Configuration

The file /etc/adduser.conf holds defaults for the programs. Every line contains a single value pair in the form “option = value”. A hash sign (#) is compulsory in a comment line.

Some of the valid configuration options are:

DSHELL	This is the log-in shell that is used for all users. Reverts to /bin/bash.
DHOME	This is the directory where the new home directories have to be created. Reverts to /home.
GROUPHOMES	The home directory is created as “/home/[groupname]/user” if set to yes. Reverts to no.
SKEL	This is the directory from which the user configuration files have to be copied. Reverts to /etc/skel.
LETTERHOMES	The home directories have an extra directory added that is the first letter of the login name if this is set to yes.

Files

/etc/adduser.conf

It is a revert layout for adduser and addgroup.

Working on addgroup command in Linux

For adding a new group

sudo addgroup groupname

This command creates a new group for our Linux Machine.

For adding a new group with a specified Group ID (GID)

sudo addgroup groupname --gid 12345

This command adds a new group with a specified Group ID (GID).

For creating a group with a specific shell

sudo addgroup groupname --shell /bin/sh

The /bin/sh shell is allocated to the newly created group with the help of this command.

For entering verbose mode

sudo addgroup groupname --debug

All the commands will be executed in the verbose mode i.e., all the details of the operations being performed will be printed, when this command is used.