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adduser command man page

USERADD(8)  System Management Commands    USERADD(8)

NAME
       useradd - create a new user or update default new user information
SYNOPSIS
       useradd [options] LOGIN

       useradd -D

       useradd -D [options]

DESCRIPTION
       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.

OPTIONS
       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 HOME_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 EXPIRE_DATE
 The date on which the user account is disabled.

       -f 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.

NOTES
       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.

CAVEATS
       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.

FILES
       /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.

EXIT VALUES
       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

SEE ALSO
       chfn(1), chsh(1), passwd(1), crypt(3), groupadd(8), groupdel(8),
       groupmod(8), login.defs(5), userdel(8), usermod(8).

System Management Commands  06/24/2006    USERADD(8)

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