The preen option to fsck (fsck -o p) checks UFS file systems and automatically fixes the simple problems that normally result from an unexpected system shutdown. It exits immediately if it encounters a problem that requires operator intervention. The preen option also permits parallel checking of file systems.
You can run fsck with the -o p option to preen the file systems after an unclean shutdown. In this mode, fsck does not look at the clean flag and does a full check. These actions are a subset of the actions that fsck takes when it runs interactively.