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man page(1) manual page
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useradd - create a new user or update default new user information
useradd [options] LOGIN
useradd -D
useradd -D [options]
When invoked without the -D option, the useradd command creates a new
user account using the values specified on the command line and 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. The version provided with
Red Hat Linux will create a group for each user added to the system by
default.
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 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, --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. /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.
- -M The user’s home directory will not be created, even if the system
-
wide settings from /etc/login.defs is to create home dirs.
- -m, --create-home
-
The user’s home directory will be created if it does not exist. The
files contained in SKEL_DIR will be copied to the home directory if
the -k option is used, otherwise the files contained in /etc/skel
will be used instead. Any directories contained in SKEL_DIR or
/etc/skel will be created in the user’s home directory as well. The
-k option is only valid in conjunction with the -m option. The
default is to not create the directory and to not copy any files.
- -l Do not add the user to the last login log file. This is an option
-
added by Red Hat.
- -n A group having the same name as the user being added to the system
-
will be created by default. This option will turn off this Red Hat
Linux specific behavior. When this option is used, users by default
will be placed in whatever group is specified in
/etc/default/useradd. If no default group is defined, group 1 will
be used.
- -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.
- -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 This flag is used to create a system account. That is, a user with a
-
UID lower than the value of UID_MIN defined in /etc/login.defs and
whose password does not expire. Note that useradd will not create a
home directory for such an user, regardless of the default setting
in /etc/login.defs. You have to specify -m option if you want a home
directory for a system account to be created. This is an option
added by Red Hat
- -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.
- -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 the -D option, useradd will either display the
current default values, or update the default values from the command
line. The valid options are
- -b, --base-dir BASE_DIR
-
The initial path prefix for a new user’s home directory. The user’s
name will be affixed to the end of HOME_DIR to create the new
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 the new user’s login shell. The named program will be
used for all future new user accounts.
If no options are specified, useradd displays the current default
values.
The system administrator is responsible for placing the default user
files in the /etc/skel/ directory.
This version of useradd was modified by Red Hat to suit Red Hat
user/group conventions.
You may not add a user to a NIS group. This must be performed on the
NIS server.
Similarly, if the username already exists in an external user database
such as NIS, useradd will deny the user account creation request.
/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/login.defs
Shadow password suite configuration.
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
chfn(1)
, chsh(1)
, passwd(1)
, crypt(3)
, groupadd(8)
, groupdel(8)
,
groupmod(8)
, login.defs(5)
, newusers(8)
, userdel(8)
, usermod(8)
.
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