NAME
useradd –
create a new user or update default new user information
SYNOPSIS
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useradd [options] |
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useradd -D |
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useradd -D |
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
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-dir 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 behavior 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.
If possible,
the ACLs and extended attributes are copied.
-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 aging,
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
-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
reset to avoid reusing the entry from a previously deleted
user.
For the
compatibility with previous Debian’s useradd, the
-O option is also supported.
-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.
By default, if
this option is not specified and CREATE_HOME is not
enabled, no home directories are created.
-M,
–no-create-home
Do no 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 -u 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 chosen 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 a
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.
-R,
–root CHROOT_DIR
Apply changes in the
CHROOT_DIR directory and use the configuration files
from the CHROOT_DIR directory.
-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 or equal to
UID_MIN and greater than every other user.
See also the
-r option and the UID_MAX description.
-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.
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 plus (‘+’) nor tilde (‘~’) nor contain a
colon (‘:’), a comma (‘,’), 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 user’s 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 overridden 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.
The default
value for GID_MIN (resp. GID_MAX) is 1000
(resp. 60000).
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.
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.
SUB_GID_MIN
(number), SUB_GID_MAX (number), SUB_GID_COUNT
(number)
If /etc/subuid exists, the
commands useradd and newusers (unless the user
already have subordinate group IDs) allocate
SUB_GID_COUNT unused group IDs from the range
SUB_GID_MIN to SUB_GID_MAX for each new
user.
The default
values for SUB_GID_MIN, SUB_GID_MAX,
SUB_GID_COUNT are respectively 100000, 600100000 and
10000.
SUB_UID_MIN
(number), SUB_UID_MAX (number), SUB_UID_COUNT
(number)
If /etc/subuid exists, the
commands useradd and newusers (unless the user
already have subordinate user IDs) allocate
SUB_UID_COUNT unused user IDs from the range
SUB_UID_MIN to SUB_UID_MAX for each new
user.
The default
values for SUB_UID_MIN, SUB_UID_MAX,
SUB_UID_COUNT are respectively 100000, 600100000 and
10000.
SYS_GID_MAX
(number), SYS_GID_MIN (number)
Range of group IDs used for the
creation of system groups by useradd,
groupadd, or newusers.
The default
value for SYS_GID_MIN (resp. SYS_GID_MAX) is
101 (resp. GID_MIN-1).
SYS_UID_MAX
(number), SYS_UID_MIN (number)
Range of user IDs used for the
creation of system users by useradd or
newusers.
The default
value for SYS_UID_MIN (resp. SYS_UID_MAX) is
101 (resp. UID_MIN-1).
UID_MAX
(number), UID_MIN (number)
Range of user IDs used for the
creation of regular users by useradd or
newusers.
The default
value for UID_MIN (resp. UID_MAX) is 1000
(resp. 60000).
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 pam_umask as the default umask value.
USERGROUPS_ENAB
(boolean)
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/subgid
Per user subordinate group
IDs.
/etc/subuid
Per user subordinate user
IDs.
/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
14
can’t update SELinux user
mapping