These programs can be used for initial conversion as well to update the shadowed file if the main file is edited by hand. Likewise, pwunconv and grpunconv are similiar. 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. Please run pwck and grpck to correct any such errors before converting to or from shadow passwords or groups.