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PASSWD(5)                        File formats                        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 user names), 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 *'s 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 a
       star in the encrypted password field to make sure that this user can
       not authenticate him- or herself using a password. (But see the Notes

       If you create a new login, first put a star 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 or a star.

              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 non-existing 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 a star, 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(1), 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).


       passwd(1), login(1), su(1), group(5), shadow(5)

                                  1998-01-05                         PASSWD(5)


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