Adding group in Linux using “groupadd” command

groupadd(8) – Linux man page

Name

groupadd – create a new group

Synopsis

groupadd [options] group

Description

The groupadd command creates a new group account using the values specified on the command line plus the default values from the system. The new group will be entered into the system files as needed.

Options

The options which apply to the groupadd command are:

-f, –force

This option causes the command to simply exit with success status if the specified group already exists. When used with -g, and the specified GID already exists, another (unique) GID is chosen (i.e. -g is turned off).

-g, –gid
GID

The numerical value of the group’s ID. This value must be unique, unless the -o option is used. The value must be non-negative. The default is to use the smallest ID value greater than 999 and greater than every other group. Values between 0 and 999 are typically reserved for system accounts.

-h, –help

Display help message and exit.

-K, –key
KEY=VALUE

Overrides /etc/login.defs defaults (GID_MIN, GID_MAX and others). Multiple -K options can be specified.

Example: -K
GID_MIN=100
-K
GID_MAX=499

Note: -K
GID_MIN=10,GID_MAX=499 doesn’t work yet.

-o, –non-unique

This option permits to add a group with a non-unique GID.

-p, –password
PASSWORD

The encrypted password, as returned by crypt(3). The default is to disable the password.

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, –system

Create a system group.

The numeric identifiers of new system groups are choosen in the SYS_GID_MINSYS_GID_MAX range, defined in login.defs, instead of GID_MINGID_MAX.

Configuration

The following configuration variables in /etc/login.defs change the behavior of this tool:

GID_MAX (number), GID_MIN (number)

Range of group IDs used for the creation of regular groups by useradd, groupadd, or newusers.

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.

SYS_GID_MAX (number), SYS_GID_MIN (number)

Range of group IDs used for the creation of system groups by useradd, groupadd, or newusers.

Files

/etc/group

Group account information.

/etc/gshadow

Secure group account information.

/etc/login.defs

Shadow password suite configuration.

Caveats

Groupnames may only be up to 32 characters long.

You may not add a NIS or LDAP group. This must be performed on the corresponding server.

If the groupname already exists in an external group database such as NIS or LDAP, groupadd will deny the group creation request.

Exit Values

The groupadd command exits with the following values:

0

success

2

invalid command syntax

3

invalid argument to option

4

GID not unique (when -o not used)

9

group name not unique

10

can’t update group file

See Also

chfn(1), chsh(1), passwd(1), gpasswd(8), groupdel(8), groupmod(8), login.defs(5), useradd(8), userdel(8), usermod(8).

By vichhaiy Posted in Linux

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