NAME

passwd − password file

DESCRIPTION

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.) 

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 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, for example, by the string ./) only the super-user will be able to change the password. 

FILES

/etc/passwd
/etc/shadow

SEE ALSO

getpwent(3C), group(4).  login(1), passwd(1), and passwd(1M) in the INTER­ACTIVE UNIX System User’s/System Administrator’s Reference Manual. 

\*U  —  Version 1.0