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

       passwd - password file

       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 asterisks (*) instead of encrypted passwords, and
       the encrypted passwords are in /etc/shadow which is readable by the
       superuser only.

       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:


       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

              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 username.
                        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).


       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.  Trying to lock an account by simply
       changing the shell field yields the same result and additionally allows
       the use of su(1).

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

       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

Linux                             1998-01-05                         PASSWD(5)


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