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RedHat 9 (Linux i386) - man page for passwd (redhat section 5)

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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.  Every-
       body 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 below.)

       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 let-

	      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.   Usu-
			ally,  it contains the full user name.	GECOS means General Electric Com-
			prehensive 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


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

					    1998-01-05					PASSWD(5)
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