Provided by: passwd_4.1.4.1-1ubuntu2_i386 bug

NAME

       pwconv, pwunconv, grpconv, grpunconv - convert to and from shadow
       passwords and groups

SYNOPSIS

       pwconv

       pwunconv

       grpconv

       grpunconv

DESCRIPTION

       The pwconv command creates shadow from passwd and an optionally
       existing shadow.

       The pwunconv command creates passwd from passwd and shadow and then
       removes shadow.

       The grpconv command creates gshadow from group and an optionally
       existing gshadow.

       The grpunconv command creates group from group and gshadow and then
       removes gshadow.

       These four programs all operate on the normal and shadow password and
       group files: /etc/passwd, /etc/group, /etc/shadow, and /etc/gshadow.

       Each program acquires the necessary locks before conversion.  pwconv
       and grpconv are similar. First, entries in the shadowed file which
       don´t exist in the main file are removed. Then, shadowed entries which
       don´t have ‘x´ as the password in the main file are updated. Any
       missing shadowed entries are added. Finally, passwords in the main file
       are replaced with ‘x´. These programs can be used for initial
       conversion as well to update the shadowed file if the main file is
       edited by hand.

       pwconv will use the values of PASS_MIN_DAYS, PASS_MAX_DAYS, and
       PASS_WARN_AGE from /etc/login.defs when adding new entries to
       /etc/shadow.

       Likewise pwunconv and grpunconv are similar. Passwords in the main file
       are updated from the shadowed file. Entries which exist in the main
       file but not in the shadowed file are left alone. Finally, the shadowed
       file is removed. Some password aging information is lost by pwunconv.
       It will convert what it can.

BUGS

       Errors in the password or group files (such as invalid or duplicate
       entries) may cause these programs to loop forever or fail in other
       strange ways. Please run pwck and grpck to correct any such errors
       before converting to or from shadow passwords or groups.

CONFIGURATION

       The following configuration variable in /etc/login.defs changes the
       behavior of grpconv and grpunconv:

       MAX_MEMBERS_PER_GROUP (number)
           Maximum members per group entry. When the maximum is reached, a new
           group entry (line) is started in /etc/group (with the same name,
           same password, and same GID).

           The default value is 0, meaning that there are no limits in the
           number of members in a group.

           This feature (split group) permits to limit the length of lines in
           the group file. This is useful to make sure that lines for NIS
           groups are not larger than 1024 characters.

           If you need to enforce such limit, you can use 25.

           Note: split groups may not be supported by all tools (even in the
           Shadow toolsuite). You should not use this variable unless you
           really need it.

       The following configuration variables in /etc/login.defs change the
       behavior of pwconv:

       PASS_MAX_DAYS (number)
           The maximum number of days a password may be used. If the password
           is older than this, a password change will be forced. If not
           specified, -1 will be assumed (which disables the restriction).

       PASS_MIN_DAYS (number)
           The minimum number of days allowed between password changes. Any
           password changes attempted sooner than this will be rejected. If
           not specified, -1 will be assumed (which disables the restriction).

       PASS_WARN_AGE (number)
           The number of days warning given before a password expires. A zero
           means warning is given only upon the day of expiration, a negative
           value means no warning is given. If not specified, no warning will
           be provided.

FILES

       /etc/login.defs
           Shadow password suite configuration.

SEE ALSO

       grpck(8), login.defs(5), pwck(8).