Provided by:
passwd_4.1.1-6ubuntu6_i386 
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.
OPTIONS
The options which apply to the useradd command are:
-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.
-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.
-D, --defaults
See below, the subsection "Changing the default values".
-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.
-e, --expiredate EXPIRE_DATE
The date on which the user account will be disabled. The date is
specified in the format YYYY-MM-DD.
-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.
The default value is -1.
-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. The default group number is 1 or whatever is
specified in /etc/default/useradd.
-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 in
/etc/default/useradd or, by default, /etc/skel.
This option may not function correctly if the username has a / in
it.
-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.
For the compatibility with previous Debian´s useradd, the -O option
is also supported.
-l
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.
By default, no home directories are created.
-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
login.defs.
-o, --non-unique
Allow the creation of a user account with a duplicate (non-unique)
UID.
-p, --password PASSWORD
The encrypted password, as returned by crypt(3). The default is to
disable the account.
-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 login.defs, instead of
UID_MIN-UID_MAX (and their GID counterparts for the creation of
groups).
-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.
-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
login.defs.
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.
-e, --expiredate EXPIRE_DATE
The date on which the user account is disabled.
-f, --inactive INACTIVE
The number of days after a password has expired before the account
will be disabled.
-g, --gid GROUP
The group name or ID for a new user´s initial group. The named
group must exist, and a numerical group ID must have an existing
entry.
-s, --shell SHELL
The name of a new user´s login shell.
NOTES
The system administrator is responsible for placing the default user
files in the /etc/skel/ directory.
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, and are only followed by lower case
letters, digits, underscores, dashes, and optionally terminated by 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.).
Usernames may only be up to 32 characters long.
CONFIGURATION
The following configuration variables in /etc/login.defs change the
behavior of this tool:
GID_MAX (number), GID_MIN (number)
Range of group IDs used for the creation of regular groups by
useradd, useradd, 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.
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 permission mask is initialized to this value. If not specified,
the permission mask will be initialized to 022.
USERGROUPS_ENAB (boolean)
FILES
/etc/passwd
User account information.
/etc/shadow
Secure user account information.
/etc/group
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
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).