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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 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:

	      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 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 out-
			put or batch jobs to the GCOS machine.	The gcos field
			in the password	file was a place to stash the informa-
			tion 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.  Trying  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)

NAME | DESCRIPTION | FILES | NOTES | SEE ALSO | COLOPHON

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