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USERADD(8) | System Management Commands | USERADD(8) |
NAME¶
useradd - create a new user or update default new user informationSYNOPSIS¶
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: -b, --base-dir BASE_DIRThe 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 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
-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 resetted
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
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 an 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.
-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_DIRThe 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. 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).
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 10000.
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 10000.
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
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/passwdUser 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: 0success
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).05/17/2017 | shadow-utils 4.2 |