groupadd(8) – Linux man page
groupadd – create a new group
groupadd [options] group
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.
The options which apply to the groupadd command are:
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).
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.
Display help message and exit.
Overrides /etc/login.defs defaults (GID_MIN, GID_MAX and others). Multiple -K options can be specified.
GID_MIN=10,GID_MAX=499 doesn’t work yet.
This option permits to add a group with a non-unique GID.
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.
Create a system group.
The numeric identifiers of new system groups are choosen in the SYS_GID_MIN–SYS_GID_MAX range, defined in login.defs, instead of GID_MIN–GID_MAX.
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.
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.
Group account information.
Secure group account information.
Shadow password suite configuration.
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.
The groupadd command exits with the following values:
invalid command syntax
invalid argument to option
GID not unique (when -o not used)
group name not unique
can’t update group file