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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),
       pwunconv(8), sulogin(8).

File Formats and Conversions      11/14/2009                         SHADOW(5)