PASSWD(4) PASSWD(4)
NAME
passwd - password file
DESCRIPTION
/etc/passwd contains for each user the following
information:
login name
password and (optional) aging
numerical user ID
numerical group ID
GCOS job number, box number, optional GCOS user ID
initial working directory
program to use as shell
This is an ASCII file. Each field within each user's entry
is separated from the next by a colon. The GCOS field is
used only when communicating with that system, and in other
installations can contain any desired information. Each
user is separated from the next by a new-line. If the shell
field is null, /bin/sh is used.
This file has user login information, and has general read
permission. It can therefore be used, for example, to map
numerical user IDs to names.
The password field consists of the character x if there is a
/etc/shadow file. If /etc/shadow does not exist, and the
login does have a password, this field will contain an
encrypted copy of the password. This field remains only for
compatibility reasons when /etc/shadow exists.
The encrypted password consists of 13 characters chosen from
a 64-character alphabet (., /, 0-9, A-Z, a-z), except when
the password is null, in which case the encrypted password
is also null. Password aging is effected for a particular
user if his encrypted password in the password file is
followed by a comma and a non-null string of characters from
the above alphabet. (Such a string must be introduced in
the first instance by the super-user.)
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PASSWD(4) PASSWD(4)
The first character of the age, M say, denotes the maximum
number of weeks for which a password is valid. A user who
attempts to login after his password has expired will be
forced to supply a new one. The next character, m say,
denotes the minimum period in weeks that must expire before
the password may be changed. The remaining one or two
characters define the week (counted from the beginning of
1970) when the password was last changed. (A null string is
equivalent to zero.) M and m have numerical values in the
range 0-63 that correspond to the 64-character alphabet
shown above (i.e., / = 1 week; z = 63 weeks). If m = M = 0
(derived from the string . or ..) the user will be forced
to change his password the next time he logs in (and the
``age'' will disappear from his entry in the password file).
If m > M (signified, e.g., by the string ./) only the
super-user will be able to change the password.
FILES
/etc/passwd
/etc/shadow
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PASSWD(4) PASSWD(4)
SEE ALSO
group(4).
getpwent(3C) in the Programmer's Reference Manual.
login(1), passwd(1) in the User's Reference Manual.
passwd(1M) in the System Administrator's Reference Manual.
Page 3 May 1989