[linux] man useradd


[linux] man useradd

[root@localhost usr]# man useradd
USERADD(8)                                             USERADD(8)

       useradd  -  Create  a  new user or update default new user

       useradd [-c comment] [-d home_dir]
               [-e expire_date] [-f inactive_time]
               [-g initial_group] [-G group[,...]]
               [-m [-k skeleton_dir] | -M] [-p passwd]
               [-s shell] [-u uid [ -o]] [-n] [-r] login

       useradd -D [-g default_group] [-b default_home]
               [-f default_inactive] [-e default_expire_date]
               [-s default_shell]

   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 -n option is
       given.  The options which apply to the useradd command are

       -c comment
              The new user's password file comment field.

       -d 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 default_home and use
              that as the login directory name.

       -e expire_date
              The date on which the user  account  will  be  dis
              abled.   The  date is specified in the format YYYY-

       -f inactive_days
              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 initial_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.
              The default group number is 1.

       -G group,[...]
              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 skele
              ton_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 skeleton_dir or /etc/skel will be cre
              ated 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 spe
              cific behavior.

       -r     This flag is used to create a system account.  That
              is, an user with an UID lower than value of UID_MIN
              defined in /etc/login.defs. 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.

       -p passwd
              The  encrypted  password,  as returned by crypt(3).
              The default is to disable the account.

       -s 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 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 dis
       play the current default values,  or  update  the  default
       values from the command line.  The valid options are

       -b default_home
              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  create the new directory
              name if the -d option is not used when  creating  a
              new account.

       -e default_expire_date
              The date on which the user account is disabled.

       -f default_inactive
              The  number  of  days  after a password has expired
              before the account will be disabled.

       -g default_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 default_shell
              The name of the new user's login shell.  The  named
              program  will  be  used  for  all  future  new user

       If no options are specified, useradd displays the  current
       default values.

       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.

       You may not add a user to an NIS group.  This must be per
       formed on the NIS server.

       /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),  crypt(3),  groupadd(8),   groupdel(8),
       groupmod(8), passwd(1), userdel(8), usermod(8)

       Julianne Frances Haugh (jfh@austin.ibm.com)

[root@localhost usr]#

Link: http://www.asm32.net/article_details.aspx?id=58

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