NAME
useradd - create a new user or update default new user information
SYNOPSIS
useradd [options] LOGIN
useradd -D
useradd -D [options]
DESCRIPTION
useradd is a low level utility for adding users. On Debian,
administrators should usually use adduser(8) instead.
When invoked without the -D option, the useradd command creates a new
user account using the values specified on the command line plus the
default values from the system. Depending on command line options, the
useradd command will update system files and may also create the new
users home directory and copy initial files.
By default, a group will also be created for the new user (see -g, -N,
-U, and USERGROUPS_ENAB).
OPTIONS
The options which apply to the useradd command are:
-b, --base-dir BASE_DIR
The default base directory for the system if -d HOME_DIR is not
specified. BASE_DIR is concatenated with the account name to
define the home directory. If the -m option is not used, BASE_DIR
must exist.
If this option is not specified, useradd will use the base
directory specified by the HOME variable in /etc/default/useradd,
or /home by default.
-c, --comment COMMENT
Any text string. It is generally a short description of the login,
and is currently used as the field for the users full name.
-d, --home HOME_DIR
The new user will be created using HOME_DIR as the value for the
users login directory. The default is to append the LOGIN name to
BASE_DIR and use that as the login directory name. The directory
HOME_DIR does not have to exist but will not be created if it is
missing.
-D, --defaults
See below, the subsection "Changing the default values".
-e, --expiredate EXPIRE_DATE
The date on which the user account will be disabled. The date is
specified in the format YYYY-MM-DD.
If not specified, useradd will use the default expiry date
specified by the EXPIRE variable in /etc/default/useradd, or an
empty string (no expiry) by default.
-f, --inactive INACTIVE
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.
If not specified, useradd will use the default inactivity period
specified by the INACTIVE variable in /etc/default/useradd, or -1
by default.
-g, --gid GROUP
The group name or number of the users initial login group. The
group name must exist. A group number must refer to an already
existing group.
If not specified, the bahavior of useradd will depend on the
USERGROUPS_ENAB variable in /etc/login.defs. If this variable is
set to yes (or -U/--user-group is specified on the command line), a
group will be created for the user, with the same name as her
loginname. If the variable is set to no (or -N/--no-user-group is
specified on the command line), useradd will set the primary group
of the new user to the value specified by the GROUP variable in
/etc/default/useradd, or 100 by default.
-G, --groups GROUP1[,GROUP2,...[,GROUPN]]]
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.
-h, --help
Display help message and exit.
-k, --skel SKEL_DIR
The skeleton directory, which contains files and directories to be
copied in the users home directory, when the home directory is
created by useradd.
This option is only valid if the -m (or --create-home) option is
specified.
If this option is not set, the skeleton directory is defined by the
SKEL variable in /etc/default/useradd or, by default, /etc/skel.
-K, --key KEY=VALUE
Overrides /etc/login.defs defaults (UID_MIN, UID_MAX, UMASK,
PASS_MAX_DAYS and others).
Example: -K PASS_MAX_DAYS=-1 can be used when creating system
account to turn off password ageing, even though system account has
no password at all. Multiple -K options can be specified, e.g.: -K
UID_MIN=100 -K UID_MAX=499
Note: -K UID_MIN=10,UID_MAX=499 doesnt work yet.
For the compatibility with previous Debians useradd, the -O option
is also supported.
-l, --no-log-init
Do not add the user to the lastlog and faillog databases.
By default, the users entries in the lastlog and faillog databases
are resetted to avoid reusing the entry from a previously deleted
user.
-m, --create-home
Create the users home directory if it does not exist. The files and
directories contained in the skeleton directory (which can be
defined with the -k option) will be copied to the home directory.
By default, no home directories are created.
-M
Do no create the users home directory, even if the system wide
setting from /etc/login.defs (CREATE_HOME) is set to yes.
-N, --no-user-group
Do not create a group with the same name as the user, but add the
user to the group specified by the -g option or by the GROUP
variable in /etc/default/useradd.
The default behavior (if the -g, -N, and -U options are not
specified) is defined by the USERGROUPS_ENAB variable in
/etc/login.defs.
-o, --non-unique
Allow the creation of a user account with a duplicate (non-unique)
UID.
This option is only valid in combination with the -o option.
-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 systems password
policy.
-r, --system
Create a system account.
System users will be created with no aging information in
/etc/shadow, and their numeric identifiers are choosen in the
SYS_UID_MIN-SYS_UID_MAX range, defined in /etc/login.defs, instead
of UID_MIN-UID_MAX (and their GID counterparts for the creation of
groups).
Note that useradd will not create a home directory for such an
user, regardless of the default setting in /etc/login.defs
(CREATE_HOME). You have to specify the -m options if you want a
home directory for a system account to be created.
-s, --shell SHELL
The name of the users login shell. The default is to leave this
field blank, which causes the system to select the default login
shell specified by the SHELL variable in /etc/default/useradd, or
an empty string by default.
-u, --uid UID
The numerical value of the users 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 user. Values between 0 and 999 are
typically reserved for system accounts.
-U, --user-group
Create a group with the same name as the user, and add the user to
this group.
The default behavior (if the -g, -N, and -U options are not
specified) is defined by the USERGROUPS_ENAB variable in
/etc/login.defs.
-Z, --selinux-user SEUSER
The SELinux user for the users login. The default is to leave this
field blank, which causes the system to select the default SELinux
user.
Changing the default values
When invoked with only the -D option, useradd will display the current
default values. When invoked with -D plus other options, useradd will
update the default values for the specified options. Valid
default-changing options are:
-b, --base-dir BASE_DIR
The path prefix for a new users home directory. The users name will
be affixed to the end of BASE_DIR to form the new users home
directory name, if the -d option is not used when creating a new
account.
This option sets the HOME variable in /etc/default/useradd.
-e, --expiredate EXPIRE_DATE
The date on which the user account is disabled.
This option sets the EXPIRE variable in /etc/default/useradd.
-f, --inactive INACTIVE
The number of days after a password has expired before the account
will be disabled.
This option sets the INACTIVE variable in /etc/default/useradd.
-g, --gid GROUP
The group name or ID for a new users initial group (when the
-N/--no-user-group is used or when the USERGROUPS_ENAB variable is
set to no in /etc/login.defs. The named group must exist, and a
numerical group ID must have an existing entry.
This option sets the GROUP variable in /etc/default/useradd.
-s, --shell SHELL
The name of a new users login shell.
This option sets the SHELL variable in /etc/default/useradd.
NOTES
The system administrator is responsible for placing the default user
files in the /etc/skel/ directory (or any other skeleton directory
specified in /etc/default/useradd or on the command line).
CAVEATS
You may not add a user to a NIS or LDAP group. This must be performed
on the corresponding server.
Similarly, if the username already exists in an external user database
such as NIS or LDAP, useradd will deny the user account creation
request.
It is usually recommended to only use usernames that begin with a lower
case letter or an underscore, followed by lower case letters, digits,
underscores, or dashes. They can end with a dollar sign. In regular
expression terms: [a-z_][a-z0-9_-]*[$]?
On Debian, the only constraints are that usernames must neither start
with a dash (-) nor contain a colon (:) or a whitespace (space: , end
of line: \n, tabulation: \t, etc.). Note that using a slash (/) may
break the default algorithm for the definition of the users home
directory.
Usernames may only be up to 32 characters long.
CONFIGURATION
The following configuration variables in /etc/login.defs change the
behavior of this tool:
CREATE_HOME (boolean)
Indicate if a home directory should be created by default for new
users.
This setting does not apply to system users, and can be overriden
on the command line.
GID_MAX (number), GID_MIN (number)
Range of group IDs used for the creation of regular groups by
useradd, groupadd, or newusers.
MAIL_DIR (string)
The mail spool directory. This is needed to manipulate the mailbox
when its corresponding user account is modified or deleted. If not
specified, a compile-time default is used.
MAIL_FILE (string)
Defines the location of the users mail spool files relatively to
their home directory.
The MAIL_DIR and MAIL_FILE variables are used by useradd, usermod, and
userdel to create, move, or delete the users mail spool.
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.
PASS_MAX_DAYS (number)
The maximum number of days a password may be used. If the password
is older than this, a password change will be forced. If not
specified, -1 will be assumed (which disables the restriction).
PASS_MIN_DAYS (number)
The minimum number of days allowed between password changes. Any
password changes attempted sooner than this will be rejected. If
not specified, -1 will be assumed (which disables the restriction).
PASS_WARN_AGE (number)
The number of days warning given before a password expires. A zero
means warning is given only upon the day of expiration, a negative
value means no warning is given. If not specified, no warning will
be provided.
SYS_GID_MAX (number), SYS_GID_MIN (number)
Range of group IDs used for the creation of system groups by
useradd, groupadd, or newusers.
SYS_UID_MAX (number), SYS_UID_MIN (number)
Range of user IDs used for the creation of system users by useradd
or newusers.
UID_MAX (number), UID_MIN (number)
Range of user IDs used for the creation of regular users by useradd
or newusers.
UMASK (number)
The file mode creation mask is initialized to this value. If not
specified, the mask will be initialized to 022.
useradd and newusers use this mask to set the mode of the home
directory they create
USERGROUPS_ENAB (boolean)
If set to yes, userdel will remove the users group if it contains
no more members, and useradd will create by default a group with
the name of the user.
FILES
/etc/passwd
User account information.
/etc/shadow
Secure user account information.
/etc/group
Group account information.
/etc/gshadow
Secure group account information.
/etc/default/useradd
Default values for account creation.
/etc/skel/
Directory containing default files.
/etc/login.defs
Shadow password suite configuration.
EXIT VALUES
The useradd command exits with the following values:
0
success
1
cant update password file
2
invalid command syntax
3
invalid argument to option
4
UID already in use (and no -o)
6
specified group doesnt exist
9
username already in use
10
cant update group file
12
cant create home directory
13
cant create mail spool
SEE ALSO
chfn(1), chsh(1), passwd(1), crypt(3), groupadd(8), groupdel(8),
groupmod(8), login.defs(5), newusers(8), userdel(8), usermod(8).