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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | NOTES | CAVEATS | CONFIGURATION | FILES | EXIT VALUES | SEE ALSO | COLOPHON |
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USERADD(8) System Management Commands USERADD(8)
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
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).
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 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
account, 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. If the directory HOME_DIR does not exist, then it will
be created unless the -M option is specified.
-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
defines the number of days after the password exceeded its
maximum age where the user is expected to replace this
password. The value is stored in the shadow password file. An
input of 0 will disable an expired password with no delay. An
input of -1 will blank the respective field in the shadow
password file. See shadow(5)for more information.
If not specified, useradd will use the default inactivity
period specified by the INACTIVE variable in
/etc/default/useradd, or -1 by default.
-F, --add-subids-for-system
Update /etc/subuid and /etc/subgid even when creating a
system account with -r option.
-g, --gid GROUP
The name or the number of the user's primary 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
1000 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.
In addition to passing in the -G flag, you can add the option
GROUPS to the file /etc/default/useradd which in turn will
add all users to those supplementary groups.
-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.
Absolute symlinks that link back to the skel directory will
have the /etc/skel prefix replaced with the user's home
directory.
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 an
account to turn off password aging. 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.
If this option is not specified, useradd will also consult
the variable LOG_INIT in the /etc/default/useradd if set to
no the user will not be added to the lastlog and faillog
databases.
-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.
The directory where the user's home directory is created must
exist and have proper SELinux context and permissions.
Otherwise the user's home directory cannot be created or
accessed.
-M, --no-create-home
Do not 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
allows the creation of an account with an already existing
UID.
This option is only valid in combination with the -u option.
As a user identity serves as key to map between users on one
hand and permissions, file ownerships and other aspects that
determine the system's behavior on the other hand, more than
one login name will access the account of the given UID.
-p, --password PASSWORD
defines an initial password for the account. PASSWORD is
expected to be encrypted, as returned by crypt (3). Within a
shell script, this option allows to create efficiently
batches of users.
Without this option, the new account will be locked and with
no password defined, i.e. a single exclamation mark in the
respective field of /etc/shadow. This is a state where the
user won't be able to access the account or to define a
password himself.
Note:Avoid this option on the command line 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.
Note that this option will not update /etc/subuid and
/etc/subgid. You have to specify the -F options if you want
to update the files 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. Only
absolute paths are supported.
-P, --prefix PREFIX_DIR
Apply changes to configuration files under the root
filesystem found under the directory PREFIX_DIR. 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
sets the path to the user's login shell. Without this option,
the system will use the SHELL variable specified in
/etc/default/useradd, or, if that is as well not set, the
field for the login shell in /etc/passwd remains empty.
-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
defines the SELinux user for the new account. Without this
option, SELinux uses the default user. Note that the shadow
system doesn't store the selinux-user, it uses semanage(8)
for that.
--selinux-range SERANGE
defines the SELinux MLS range for the new account. Without
this option, SELinux uses the default range. Note that the
shadow system doesn't store the selinux-range, it uses
semanage(8) for that.
This option is only valid if the -Z (or --selinux-user)
option is specified.
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
sets 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
sets the date on which newly created user accounts are
disabled.
This option sets the EXPIRE variable in /etc/default/useradd.
-f, --inactive INACTIVE
defines the number of days after the password exceeded its
maximum age where the user is expected to replace this
password. See shadow(5)for more information.
This option sets the INACTIVE variable in
/etc/default/useradd.
-g, --gid GROUP
sets the default primary group for newly created users,
accepting group names or a numerical group ID. The named
group must exist, and the GID must have an existing entry.
This option sets the GROUP variable in /etc/default/useradd.
-s, --shell SHELL
defines the default login shell for new users.
This option sets the SHELL variable in /etc/default/useradd.
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).
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.
Usernames may contain only lower and upper case letters, digits,
underscores, or dashes. They can end with a dollar sign. Dashes
are not allowed at the beginning of the username. Fully numeric
usernames and usernames . or .. are also disallowed. It is not
recommended to use usernames beginning with . character as their
home directories will be hidden in the ls output.
Usernames may only be up to 256 characters long.
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.
The parameter CREATE_MAIL_SPOOL in /etc/default/useradd
determines whether the mail spool should be created.
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, 0 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 value of -1 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.
/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/shadow-maint/useradd-pre.d/*,
/etc/shadow-maint/useradd-post.d/*
Run-part files to execute during user addition. The
environment variable ACTION will be populated with useradd
and SUBJECT with the username. useradd-pre.d will be
executed prior to any user addition. useradd-post.d will
execute after user addition. If a script exits non-zero then
execution will terminate.
/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.
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 or group name already in use
10
can't update group file
12
can't create home directory
14
can't update SELinux user mapping
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).
This page is part of the shadow-utils (utilities for managing
accounts and shadow password files) project. Information about
the project can be found at
⟨https://github.com/shadow-maint/shadow⟩. If you have a bug
report for this manual page, send it to
[email protected]. This page was obtained
from the project's upstream Git repository
⟨https://github.com/shadow-maint/shadow⟩ on 2024-06-15. (At that
time, the date of the most recent commit that was found in the
repository was 2024-06-13.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
shadow-utils 4.14.0 06/15/2024 USERADD(8)
Pages that refer to this page: getsubids(1), homectl(1), newgidmap(1), newuidmap(1), subgid(5), subuid(5), chpasswd(8), groupadd(8), groupdel(8), groupmems(8), groupmod(8), newusers(8), userdel(8), usermod(8)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|