Provided by: passwd_4.8.1-2ubuntu2.2_amd64 
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 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.
-P, --prefix PREFIX_DIR
Apply changes in the PREFIX_DIR directory and use the configuration files from the
PREFIX_DIR directory. 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
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.
On Ubuntu, the same constraints as Debian are in place, with the additional constraint
that the username cannot be fully numeric. This includes octal and hexadecimal syntax.
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.
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 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/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
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).