useradd(1M) useradd(1M)
NAME [Toc] [Back]
useradd - add a new user login to the system
SYNOPSIS [Toc] [Back]
useradd [-u uid [-o] ] [-g group] [-G group [, group...]] [-d dir]
[-s shell] [-c comment] [-m [-k skel_dir]] [-f inactive]
[-e expire] [-r update_homedir_ownership] login
useradd -D [-g group] [-b base_dir] [-f inactive] [-e expire]
[-r update_homedir_ownership]
DESCRIPTION [Toc] [Back]
The useradd command creates a user login on the system by adding the
appropriate entry to the /etc/passwd file and any security files,
modifying the /etc/group file as necessary, creating a home directory,
and copying the appropriate default files into the home directory
depending on the command line options. The new login remains locked
until the passwd (see passwd(1)) command is invoked.
New Behavior [Toc] [Back]
login will not be added to the primary group entry in the /etc/group
file, even if the primary group is specified in the command line.
However, the login is added to the corresponding supplemental group
in /etc/group file.
Options [Toc] [Back]
The useradd command supports the following options:
-u uid Specifies the UID for the new user. uid must be a
non-negative decimal integer less than MAXUID as
it is defined in the <param.h> header file. uid
defaults to the next available unique number above
the maximum currently assigned number. UIDs from
0-99 are reserved.
-o Allows the UID to be non-unique (i.e., a
duplicate).
-g group Specifies the integer group ID or character string
name of an existing group. This defines the
primary group membership of the new login. The
default for this option can be reset by invoking
useradd -D -g group.
-G group Specifies the integer group ID or character string
name of an existing group. This defines the
supplemental group memberships of the new login.
Multiple groups may be specified as a comma
separated list. Duplicates within group with the
-g and -G options are ignored.
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-d dir Specifies the home directory of the new login. It
defaults to base_dir/login, where login is the new
login and base_dir is the base directory for new
login home directories.
To specify directory creation, you must use the -m
option.
-s shell Specifies the full pathname of the new login
shell. The default is an empty field, which
causes the system to use /sbin/sh as the login
shell. The value of shell must be a valid
executable file.
-c comment Specifies the comment field present in the
/etc/passwd entry for this login. This can be any
text string. A short description of the new login
is suggested for this field.
-m Creates the home directory for the new login if it
does not exist. If the home directory exists, the
directory must have read and execute permission by
group, where group is the primary group of the new
login. The -m option must be used to create a
home directory.
-k skel_dir Specifies the skeleton directory that contains
information that can be copied to the new login's
home directory. This directory must exist. The
system provides a skeleton directory, /etc/skel,
that can be used for this purpose.
-f inactive Specifies the maximum number of days of continuous
inactivity of the login before the login is
declared invalid. Normal values are positive
integers, while a value of -1 defeats this status.
-e expire Specifies the date on which this login can no
longer be used. After expire, no user will be
able to access this login. This option is used to
create temporary logins. expire, which is a date,
may be typed in any format, except a Julian date.
For example, a date may be entered in either of
the following formats:
July 13, 1993
7/13/93
A value of '''' defeats the expired date status.
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-D Manages the defaults for various options. When
useradd is invoked with this option only, the
default values for group, base_dir, skel_dir,
shell, inactive, expire, and
update_homedir_ownership are displayed. Invoking
useradd with this option and other allowed options
sets the default values for those options.
-b base_dir Specifies the default base directory for the
system. If -d dir is not specified, base_dir is
concatenated with the new login name to define the
path of the new home directory. base_dir must
exist.
-r update_homedir_ownership
By default, useradd will not recursively update
the ownership of the home directory for the new
user if the directory exists and is not a shared
home directory. This behavior of useradd can be
changed using -r [yes|no] option. When used with
the -D option it will set the default behavior.
This option takes the argument yes or no:
yes useradd will recursively update the
ownership of the home directory and the
files/directories below it to the new user,
if the directory already exists and is not a
shared home directory.
no useradd will not update the ownership of the
home directory and the files/directories
below it.
The useradd command may be used with the login argument, where login
is the new login name, specified as a string of printable characters.
It may not contain a colon (:) or a newline (\n).
Unless enhanced security is installed, the -e and -f options are not
supported and will return an error.
Networking Features [Toc] [Back]
NIS
This command is aware of NIS user and group entries. Only local users
and groups may be modified with this command. Attempts to modify an
NIS user or group will result in an error. NIS users and groups must
be administered from the NIS server. NIS users are checked when
verifying uniqueness of the new UID or new user name, which may result
in the error
login x not unique
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useradd(1M) useradd(1M)
(return value 9), or the error
UID # is not unique (when -o is not used)
(return value 4) even though the user or UID is not present in the
local /etc/passwd file. The error
Cannot modify /etc/group file, /etc/passwd was modified
(return value 10) is returned if a group specified with either the -g
option or the -G option is an NIS group (see group(4)).
NFS [Toc] [Back]
Errors may occur with the -m or -k options if the indicated directory
is within an NFS mounted file system that does not allow root
privileges across the NFS mount, and the directory or files within the
directory do not have sufficient permissions.
RETURN VALUE [Toc] [Back]
useradd exits with one of the following values:
0 Successful completion.
2 Invalid command syntax.
3 Invalid argument supplied to an option.
4 uid is not unique (when -o is not used).
6 The group specified with the -g option does not exist.
9 login is not unique.
10 Cannot modify the /etc/group file. The login was added to
the /etc/passwd file, but not to the /etc/group file.
12 Unable to create the home directory (while using the -m
option) or unable to complete the copy of skel_dir to the
new home directory.
13 Unable to open /etc/ptmp file or /etc/default file, or
/etc/passwd file is non-existent.
14 /etc/passwd, or /etc/ptmp, or /etc/default file busy.
Another command may be modifying the /etc/passwd file.
16 Cannot add the entry into the /etc/passwd file.
EXAMPLES [Toc] [Back]
Add the user otto to the system with all of the default attributes.
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useradd otto
Add the user otto to the system with a UID of 222 and a primary group
of staff.
useradd -u 222 -g staff otto
List the defaults for the primary group, base directory, inactivity
timeout, and skeleton directory.
useradd -D
Change the default primary group to staff.
useradd -D -g staff
WARNINGS [Toc] [Back]
A directory can be shared between the users belonging to the same
group. If the home directory is in the unshared mode and a new user
is allocated to that directory then it will be put into the shared
mode by setting the permissions of that directory to 775 (i.e.
includes the write permissions to the group as well). Also, the
directory which will be shared should have read and execute
permissions for the group. Otherwise, useradd will report an error.
As many users may try to write the /etc/passwd file simultaneously, a
passwd locking mechanism was deviced. If this locking fails after
subsequent retrying, useradd terminates.
A group entry in the /etc/group file can have maximum of LINE_MAX
bytes. If a user is added to a group that has reached LINE_MAX limit,
another entry of the same group is created to which the new user is
added. A warning message is also issued.
FILES [Toc] [Back]
/etc/shadow Shadow Password file
/etc/passwd System Password file
/etc/skel Skeleton directory
/etc/group System group file
/etc/ptmp Lock file used when updating password file
SEE ALSO [Toc] [Back]
passwd(1), users(1), groupadd(1M), groupdel(1M), groupmod(1M),
logins(1M), userdel(1M), usermod(1M), pwconv(1M), group(4), shadow(4).
STANDARDS CONFORMANCE [Toc] [Back]
useradd: SVID3
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