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
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 /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 themself using a password. (But see
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
The field are as follows:
- This is the user's login name. It should not contain capital letters.
- This is either the encrypted user password, an asterisk (*), or the letter
'x'. (See pwconv(8) for an explanation of 'x'.)
- The privileged root login account (superuser) has the user ID
- 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'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.
If you want to create user groups, there must be an entry in /etc/group,
or no group will exist.
- 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.
- 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
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).
chfn(1), chsh(1), login(1), passwd(1), su(1),
crypt(3), getpwent(3), getpwnam(3), group(5),
This page is part of release 5.05 of the Linux man-pages project. A
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version of this page, can be found at https://www.kernel.org/doc/man-pages/.