Man page 8 : useradd

useradd - create a new user or update default new user information

useradd [options] LOGIN useradd -D useradd -D [options]

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 userAqs 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:

-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.

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 userAqs full name.

-d, --home HOME_DIR
    The new user will be created using HOME_DIR as the value for the userAqs 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 userAqs 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 userAqs 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 userAqs entries in the lastlog and faillog databases are resetted to avoid reusing the entry from a previously deleted user.

For the compatibility with previous DebianAqs useradd, the -O option is also supported.

-m, --create-home
    Create the userAqs 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 userAqs 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 systemAqs 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.

-s, --shell SHELL
    The name of the userAqs 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 userAqs 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 /etc/login.defs.

-Z, --selinux-user SEUSER
    The SELinux user for the userAqs login. The default is to leave this field blank, which causes the system to select the default SELinux user.

4.1. Changing the default values ▲

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.

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 (Aq-Aq) nor contain a colon (Aq:Aq) or a whitespace (space: Aq Aq, end of line: Aq\nAq, tabulation: Aq\tAq, etc.). Note that using a slash (Aq/Aq) may break the default algorithm for the definition of the userAqs home directory.

Usernames may only be up to 32 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.

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 userAqs 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 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 userAqs 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/skel/
    Directory containing default files.

/etc/login.defs
    Shadow password suite configuration.

The useradd command exits with the following values:

0
    success

1
    canAqt update password file

2
    invalid command syntax

3
    invalid argument to option

4
    UID already in use (and no -o)

6
    specified group doesnAqt exist

9
    username already in use

10
    canAqt update group file

12
    canAqt create home directory

13
    canAqt 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).