PASSWD(5)                                           Linux Programmer's Manual                                          PASSWD(5)



NAME
       passwd - password file

DESCRIPTION
       Passwd  is  a  text  file, that contains a list of the system's accounts, giving for each account some useful information
       like user ID, group ID, home directory, shell, etc.  Often, it also contains the encrypted passwords  for  each  account.
       It should have general read permission (many utilities, like ls(1) use it to map user IDs to usernames), but write access
       only for the superuser.

       In the good old days there was no great problem with this general read permission.  Everybody could  read  the  encrypted
       passwords,  but  the hardware was too slow to crack a well-chosen password, and moreover, the basic assumption used to be
       that of a friendly user-community.  These days many  people  run  some  version  of  the  shadow  password  suite,  where
       /etc/passwd  has  "x" instead of encrypted passwords, and the encrypted passwords are in /etc/shadow which is readable by
       the superuser only.

       If the encrypted password, whether in /etc/passwd or in /etc/shadow, is an empty string, login is  allowed  without  even
       asking  for a password.  Note that this functionality may be intentionally disabled in applications, or configurable (for
       example using the "nullok" or "nonull" arguments to pam_unix.so).

       If the encrypted password in /etc/passwd is "*NP*" (without the quotes), the shadow record should be obtained from a NIS+
       server.

       Regardless  of  whether shadow passwords are used, many sysadmins use an asterisk in the encrypted password field to make
       sure that this user can not authenticate him- or herself using a password.  (But see the Notes below.)

       If you create a new login, first put an asterisk in the password field, then use passwd(1) to set it.

       There is one entry per line, and each line has the format:

              account:password:UID:GID:GECOS:directory:shell

       The field descriptions are:

              account   the name of the user on the system.  It should not contain capital letters.

              password  the encrypted user password, an asterisk (*), or the letter 'x'.  (See pwconv(8) for an  explanation  of
                        'x'.)

              UID       the numerical user ID.

              GID       the numerical primary group ID for this user.

              GECOS     This  field  is  optional and only used for informational purposes.  Usually, it contains the full user-
                        name.  GECOS means General Electric Comprehensive Operating System, which has been renamed to GCOS  when
                        GE's  large  systems  division  was  sold to Honeywell.  Dennis Ritchie has reported: "Sometimes we sent
                        printer output or batch jobs to the GCOS machine.  The gcos field in the password file was  a  place  to
                        stash the information for the $IDENTcard.  Not elegant."

              directory the user's $HOME directory.

              shell     the  program to run at login (if empty, use /bin/sh).  If set to a nonexistent executable, the user will
                        be unable to login through login(1).

FILES
       /etc/passwd

NOTES
       If you want to create user groups, their GIDs must be equal and there must be an entry in /etc/group, or  no  group  will
       exist.

       If  the  encrypted  password  is set to an asterisk, the user will be unable to login using login(1), but may still login
       using rlogin(1), run existing processes and initiate new ones through rsh(1), cron(8), at(1), or mail filters, etc.  Try-
       ing  to  lock  an  account  by  simply changing the shell field yields the same result and additionally allows the use of
       su(1).

SEE ALSO
       login(1), passwd(1), su(1), getpwent(3), getpwnam(3), group(5), shadow(5)

COLOPHON
       This page is part of release 3.25 of the Linux man-pages project.  A description of the project,  and  information  about
       reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



Linux                                                      1998-01-05                                                  PASSWD(5)