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USERADD


Section: System Management Commands (8)
Updated: 07/24/2009
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NAME

useradd – create a new user or update default new user information
 

SYNOPSIS



useradd [options] LOGIN

useradd -D

useradd -D [options]

 

DESCRIPTION

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 user’s 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 user’s full name.

-d, –home 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
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 user’s 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 user’s 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
doesn’t work yet.

-l, –no-log-init


Do not add the user to the lastlog and faillog databases.


By default, the user’s entries in the lastlog and faillog databases are resetted to avoid reusing the entry from a previously deleted user.

-m, –create-home


Create the user’s 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.


useradd will create the home directory unless CREATE_HOME in /etc/login.defs is set to no.

-M


Do not create the user’s 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 system’s 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 user’s 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 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 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 user’s 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 user’s home directory. The user’s name will be affixed to the end of
BASE_DIR
to form the new user’s 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 user’s 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 user’s 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.

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 user’s mail spool.

If
MAIL_CHECK_ENAB
is set to
yes, they are also used to define the
MAIL
environment variable.

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


It is also used by
login
to define users’ initial umask. Note that this mask can be overriden by the user’s GECOS line (if
QUOTAS_ENAB
is set) or by the specification of a limit with the
K
identifier in
limits(5).

USERGROUPS_ENAB (boolean)


Enable setting of the umask group bits to be the same as owner bits (examples: 022 -> 002, 077 -> 007) for non-root users, if the uid is the same as gid, and username is the same as the primary group name.


If set to
yes,
userdel
will remove the user’s 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


can’t update password file

2


invalid command syntax

3


invalid argument to option

4


UID already in use (and no
-o)

6


specified group doesn’t exist

9


username already in use

10


can’t update group file

12


can’t create home directory

13


can’t create mail spool

14


can’t update SELinux user mapping

 

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).



 

Index



NAME

SYNOPSIS

DESCRIPTION

OPTIONS


Changing the default values


NOTES

CAVEATS

CONFIGURATION

FILES

EXIT VALUES

SEE ALSO



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