SHADOW(5) File Formats and Conversions SHADOW(5)
shadow - encrypted password file
shadow contains the encrypted password information for user's accounts
and optional the password aging information. Included is:
o login name
o encrypted password
o days since Jan 1, 1970 that password was last changed
o days before password may be changed
o days after which password must be changed
o days before password is to expire that user is warned
o days after password expires that account is disabled
o days since Jan 1, 1970 that account is disabled
o a reserved field
The password field must be filled. The encrypted password consists of
13 to 24 characters from the 64 character alphabet a thru z, A thru Z,
0 thru 9, \. and /. Optionally it can start with a "$" character. This
means the encrypted password was generated using another (not DES)
algorithm. For example if it starts with "$1$" it means the MD5-based
algorithm was used.
Refer to crypt(3) for details on how this string is interpreted.
If the password field contains some string that is not valid result of
crypt(3), for instance ! or *, the user will not be able to use a unix
password to log in, subject to pam(7).
The date of the last password change is given as the number of days
since Jan 1, 1970. The password may not be changed again until the
proper number of days have passed, and must be changed after the
maximum number of days. If the minimum number of days required is
greater than the maximum number of day allowed, this password may not
be changed by the user.
An account is considered to be inactive and is disabled if the password
is not changed within the specified number of days after the password
expires. An account will also be disabled on the specified day
regardless of other password expiration information.
This information supersedes any password or password age information
present in /etc/passwd.
This file must not be readable by regular users if password security is
to be maintained.
User account information.
Secure user account information.
chage(1), login(1), su(1), passwd(1), passwd(5), pwconv(8),
File Formats and Conversions 11/14/2009 SHADOW(5)