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.
This version of useradd will create a group for each
user added to the system, unless -n option is given.
This behavior was introduced by Red Hat Software.
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 format YYYY-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 in skeleton_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_dir or /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
setting in /etc/login.defs is to create home directories.
-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-style behavior.
-r
This flag is used to create a system account. That is, a user with an
UID lower than value of UID_MIN defined in /etc/login.defs. Note
that useradd will not create a home directory for such a user
regardless of the 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 Software.
-p passwd
The encrypted password as returned by crypt(3).
The default is to disable the account.
-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.
-k default_skeleton_dir
The name of the new skeleton directory.
If no options are specified, useradd displays the current
default values.
NOTES
The system administrator is responsible for placing the default
user files in the skeleton directory (/etc/skel or directory
defined in /etc/default/useradd file).
CAVEATS
You may not add a user to an NIS group.
This must be performed on the NIS server.
FILES
/etc/passwd - user account information
/etc/shadow - secure user account information
/etc/group - group information
/etc/default/useradd - default information
/etc/login.defs - system-wide settings
/etc/skel - directory containing default files
