Section (5) passwd
passwd — password file
/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
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 _zsingle_quotesz_x_zsingle_quotesz_
character in the password field, and the encrypted passwords
/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 password. 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
*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 themself 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:
The field are as follows:
This is the user_zsingle_quotesz_s login name. It should not contain capital letters.
This is either the encrypted user password, an asterisk (*), or the letter _zsingle_quotesz_x_zsingle_quotesz_. (See pwconv(8) for an explanation of _zsingle_quotesz_x_zsingle_quotesz_.)
rootlogin account (superuser) has the user ID 0.
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)).
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_zsingle_quotesz_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.
This is the user_zsingle_quotesz_s home directory: the initial directory where the user is placed after logging in. The value in this field is used to set the
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
If you want to create user groups, there must be an entry
/etc/group, or no group will
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).
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Copyright (c) 1993 Michael Haardt (michaelmoria.de),
Fri Apr 2 11:32:09 MET DST 1993
This is free documentation; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of
the License, or (at your option) any later version.
The GNU General Public License_zsingle_quotesz_s references to object code
and executables are to be interpreted as the output of any
document formatting or typesetting system, including
intermediate and printed output.
This manual is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public
License along with this manual; if not, see
Modified Sun Jul 25 10:46:28 1993 by Rik Faith (faithcs.unc.edu)
Modified Sun Aug 21 18:12:27 1994 by Rik Faith (faithcs.unc.edu)
Modified Sun Jun 18 01:53:57 1995 by Andries Brouwer (aebcwi.nl)
Modified Mon Jan 5 20:24:40 MET 1998 by Michael Haardt