USERADD linux command manual
useradd - Create a new user or update default new user information
useradd [-c comment] [-d home_dir]
[-e expire_date] [-f inactive_time]
[-g initial_group] [-G group[,...]]
[-m [-k skeleton_dir] | -M] [-n] [-o] [-p passwd] [-r]
[-s shell] [-u uid] login
useradd -D [-g default_group] [-b default_home]
[-e default_expire_date] [-f default_inactive]
Creating New Users
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. The new user account will be entered
into the system files as needed, the home directory will be created,
and initial files copied, depending on the command line options. The
version provided with Red Hat Linux will create a group for each user
added to the system, unless the -n option is given. The options which
apply to the useradd command are:
The new user's password file comment field.
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 default_home and use that as the login directory name.
The date on which the user account will be disabled. The date
is specified in the format YYYY-MM-DD.
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.
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. The default group number is 1 or what-
ever is specified in /etc/default/useradd.
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.
-m The user's home directory will be created if it does not exist.
The files contained in skeleton_dir will be copied to the home
directory if the -k option is used, otherwise the files con-
tained in /etc/skel will be used instead. Any directories con-
tained in skeleton_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.
-M The user home directory will not be created, even if the system
wide settings from /etc/login.defs is to create home dirs.
-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.
-o Allow create user with duplicate (non-unique) UID.
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.
The name of the user's login shell. The default is to leave
this field blank, which causes the system to select the default
-u 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 99 and greater than every other user. Values between 0
and 99 are typically reserved for system accounts.
Changing the default values
When invoked with the -D option, useradd will either display the cur-
rent default values, or update the default values from the command
line. The valid options are
The initial path prefix for a new user's home directory. The
user's name will be affixed to the end of default_home to cre-
ate the new directory name if the -d option is not used when
creating a new account.
The date on which the user account is disabled.
The number of days after a password has expired before the
account will be disabled.
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 exist-
ing entry .
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 val-
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
You may not add a user to an NIS group. This must be performed on the
/etc/passwd - user account information
/etc/shadow - secure user account information
/etc/group - group information
/etc/gshadow - secure group information
/etc/default/useradd - default information
/etc/login.defs - system-wide settings
/etc/skel - directory containing default files
chfn(1), chsh(1), passwd(1), crypt(3), groupadd(8), groupdel(8),
groupmod(8), userdel(8), usermod(8)
Julianne Frances Haugh (firstname.lastname@example.org)