Support for shadow passwords has been enhanced significantly for Red Hat Linux 5.1. The shadow-utils package contains a number of utilities that support:

• Conversion from normal to shadowed passwords and back (pwconv,
  pwunconv).

• Verification of the password, group, and associated shadow files (pwck,
  grpck).

• Industry-standard methods of adding, deleting and modifying user accounts (useradd, usermod, and userdel).

• Industry-standard methods of adding, deleting, and modifying user groups (groupadd, groupmod, and groupdel).

• Industry-standard method of administering the /etc/group file
  (gpasswd).

Please Note: There are a few additional points of interest concerning these utilities: