How to use the useradd command

useradd - Create a new user or update default new user information

SYNOPSIS

useradd [-c comment] [-d home_dir]

[-e expire_date] [-f inactive_time] [-g initial_group] [-G group[,...]] [-m [-k skeleton_dir] | -M] [-n] [-o] [-p passwd] [-r] [-s shell] [-u uid] login

useradd -D [-g default_group] [-b default_home]

[-e default_expire_date] [-f default_inactive] [-s default_shell]

DESCRIPTION

Creating New Users

When invoked without the -D option, the useradd command creates a new user account using the values specified on the command line and the default values from the system. The new user account will be entered into the system files as needed, the home directory will be created, and initial files copied, depending on the command line options. The version provided with Red Hat Linux will create a group for each user added to the system, unless the -n option is given. The options which apply to the useradd command are:

-c comment

The new user's password file comment field.

-d home_dir

The new user will be created using home_dir as the value for the user's login directory. The default is to append the login name to default_home and use that as the login directory name.

-e expire_date

The date on which the user account will be disabled. The date is specified in the formatYYYY-MM-DD.

-f inactive_days

The number of days after a password expires until the account is permanently disabled. A value of 0 disables the account as soon as the password has expired, and a value of -1 disables the feature. The default value is -1.

-g initial_group

The group name or number of the user's initial login group. The group name must exist. A group number must refer to an already existing group. The default group number is 1 or whatever is specified in /etc/default/useradd.

-G group,[...]

A list of supplementary groups which the user is also a member of. Each group is separated from the next by a comma, with no intervening whitespace. The groups are subject to the same restrictions as the group given with the -g option. The default is for the user to belong only to the initial group.

-m

The user's home directory will be created if it does not exist. The files contained inskeleton_dir will be copied to the home directory if the -k option is used, otherwise the files contained in /etc/skel will be used instead. Any directories contained in skeleton_diror /etc/skel will be created in the user's home directory as well. The -k option is only valid in conjunction with the -m option. The default is to not create the directory and to not copy any files.

-M

The user home directory will not be created, even if the system wide settings from/etc/login.defs is to create home dirs.

-n

A group having the same name as the user being added to the system will be created by default. This option will turn off this Red Hat Linux specific behavior.

-o

Allow create user with duplicate (non-unique) UID.

-p passwd

The encrypted password, as returned by crypt. The default is to disable the account.

-r

This flag is used to create a system account. That is, a user with a UID lower than the value of UID_MIN defined in /etc/login.defs and whose password does not expire. Note that useradd will not create a home directory for such an user, regardless of the default setting in /etc/login.defs. You have to specify -m option if you want a home directory for a system account to be created. This is an option added by Red Hat.

-s shell

The name of the user's login shell. The default is to leave this field blank, which causes the system to select the default login shell.

-u uid

The numerical value of the user'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 99 and greater than every other user. Values between 0 and 99 are typically reserved for system accounts.

Changing the default values

When invoked with the -D option, useradd will either display the current default values, or update the default values from the command line. The valid options are

-b default_home

The initial path prefix for a new user's home directory. The user's name will be affixed to the end of default_home to create the new directory name if the -d option is not used when creating a new account.

-e default_expire_date

The date on which the user account is disabled.

-f default_inactive

The number of days after a password has expired before the account will be disabled.

-g default_group

The group name or ID for a new user's initial group. The named group must exist, and a numerical group ID must have an existing entry .

-s default_shell

The name of the new user's login shell. The named program will be used for all future new user accounts.

If no options are specified, useradd displays the current default values.

Posted in: Basics