USERADD(8) System Management Commands USERADD(8)
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
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:
--badname
Allow names that do not conform to standards.
-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 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
account, 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. If the directory
HOME_DIR does not exist, then it will be created unless the -M
option is specified.
-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
defines the number of days after the password exceeded its maximum
age where the user is expected to replace this password. The value
is stored in the shadow password file. An input of 0 will disable
an expired password with no delay. An input of -1 will blank the
respective field in the shadow password file. See shadow(5)for more
information.
If not specified, useradd will use the default inactivity period
specified by the INACTIVE variable in /etc/default/useradd, or -1
by default.
-F, --add-subids-for-system
Update /etc/subuid and /etc/subgid even when creating a system
account with -r option.
-g, --gid GROUP
The name or the number of the user's primary 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 an account
to turn off password aging. Multiple -K options can be specified,
e.g.: -K UID_MIN =100 -K UID_MAX=499
For the compatibility with previous Debian's 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 user's entries in the lastlog and faillog databases
are reset to avoid reusing the entry from a previously deleted
user.
If this option is not specified, useradd will also consult the
variable LOG_INIT in the /etc/default/useradd if set to no the user
will not be added to the lastlog and faillog databases.
-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.
The directory where the user's home directory is created must exist
and have proper SELinux context and permissions. Otherwise the
user's home directory cannot be created or accessed.
-M, --no-create-home
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
allows the creation of an account with an already existing UID.
This option is only valid in combination with the -u option. As a
user identity serves as key to map between users on one hand and
permissions, file ownerships and other aspects that determine the
system's behavior on the other hand, more than one login name will
access the account of the given UID.
-p, --password PASSWORD
defines an initial password for the account. PASSWORD is expected
to be encrypted, as returned by crypt (3). Within a shell script,
this option allows to create efficiently batches of users.
Without this option, the new account will be locked and with no
password defined, i.e. a single exclamation mark in the respective
field of /etc/shadow. This is a state where the user won't be able
to access the account or to define a password himself.
Note:Avoid this option on the command line 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.
Note that this option will not update /etc/subuid and /etc/subgid.
You have to specify the -F options if you want to update the files
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. Only absolute paths are
supported.
-P, --prefix PREFIX_DIR
Apply changes to configuration files under the root filesystem
found under the directory PREFIX_DIR. This option does not chroot
and is intended for preparing a cross-compilation target. Some
limitations: NIS and LDAP users/groups are not verified. PAM
authentication is using the host files. No SELINUX support.
-s, --shell SHELL
sets the path to the user's login shell. Without this option, the
system will use the SHELL variable specified in
/etc/default/useradd, or, if that is as well not set, the field for
the login shell in /etc/passwd remains empty.
-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
defines the SELinux user for the new account. Without this option,
a SELinux uses the default user. Note that the shadow system
doesn't store the selinux-user, it uses semanage(8) for that.
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
sets 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
sets the date on which newly created user accounts are disabled.
This option sets the EXPIRE variable in /etc/default/useradd.
-f, --inactive INACTIVE
defines the number of days after the password exceeded its maximum
age where the user is expected to replace this password. See
shadow(5)for more information.
This option sets the INACTIVE variable in /etc/default/useradd.
-g, --gid GROUP
sets the default primary group for newly created users, accepting
group names or a numerical group ID. The named group must exist,
and the GID must have an existing entry.
This option sets the GROUP variable in /etc/default/useradd.
-s, --shell SHELL
defines the default login shell for new users.
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 contain only lower and upper case letters, digits,
underscores, or dashes. They can end with a dollar sign. Dashes are not
allowed at the beginning of the username. Fully numeric usernames and
usernames . or .. are also disallowed. It is not recommended to use
usernames beginning with . character as their home directories will be
hidden in the ls output.
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).
HOME_MODE (number)
The mode for new home directories. If not specified, the UMASK is
used to create the mode.
useradd and newusers use this to set the mode of the home directory
they create.
LASTLOG_UID_MAX (number)
Highest user ID number for which the lastlog entries should be
updated. As higher user IDs are usually tracked by remote user
identity and authentication services there is no need to create a
huge sparse lastlog file for them.
No LASTLOG_UID_MAX option present in the configuration means that
there is no user ID limit for writing lastlog entries.
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. The parameter
CREATE_MAIL_SPOOL in /etc/default/useradd determines whether the
mail spool should be created.
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, 0 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 65536.
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 65536.
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 if HOME_MODE is not set.
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/shadow-maint/useradd-pre.d/*, /etc/shadow-maint/useradd-post.d/*
Run-part files to execute during user addition. The environment
variable ACTION will be populated with useradd and SUBJECT with the
username. useradd-pre.d will be executed prior to any user
addition. useradd-post.d will execute after user addition. If a
script exits non-zero then execution will terminate.
/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 or group name already in use
10
can't update group file
12
can't create home directory
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), subgid(5), subuid(5),
userdel(8), usermod(8).
shadow-utils 4.13 03/23/2023 USERADD(8)
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