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

NAME

       passwd - password file

DESCRIPTION

       The  /etc/passwd  file  is  a  text file that describes user login accounts for the system.  It should have read permission allowed for all
       users (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 an 'x' character in the password field, 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 pass-
       word.  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 an NIS+ server.

       Regardless  of  whether	shadow	passwords are used, many system administrators 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 NOTES below.)

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

       Each line of the file describes a single user, and contains seven colon-separated fields:

	      name:password:UID:GID:GECOS:directory:shell

       The field are as follows:

       name	   This is the user's login name.  It should not contain capital letters.

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

       UID	   The privileged root login account (superuser) has the user ID 0.

       GID	   This is the numeric primary group ID for this user.	(Additional groups for the user are defined in the system group file;  see
		   group(5)).

       GECOS	   This  field	(sometimes called the "comment field") is optional and used only for informational purposes.  Usually, it contains
		   the full username.  Some programs (for example, finger(1)) display information from this field.

		   GECOS stands for "General Electric Comprehensive Operating System", which was 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   This is the user's home directory: the initial directory where the user is placed after logging in.	The value in this field is
		   used to set the HOME environment variable.

       shell	   This  is  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).  The value in this field is used to set the SHELL environment variable.

FILES

       /etc/passwd

NOTES

       If you want to create user groups, 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), crypt(3), group(5), shadow(5)

COLOPHON

       This page is part of release 3.53 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								    2012-05-03								 PASSWD(5)