hfsdebug is a filesystem debugger for Apple’s HFS Plus (hereafter referred to as HFS+) volume format. The term “debugger” may be somewhat of a misnomer for hfsdebug, because a key feature (rather, a limitation) of it is that it operates on an HFS+ volume only in read-only mode. Thus, it cannot currently be used by itself to repair any defects in a volume, or to even write to a volume in any manner whatsoever. Nevertheless, hfsdebug is meant to be a useful tool in exploring HFS+ internals, as it allows you to browse, inspect, and analyze various aspects of HFS+ volumes. It can also calculate and display certain filesystem statistics. The original intent in creating hfsdebug was to quantify filesystem fragmentation under HFS+. hfsdebug is a PPC binary that also runs on Intel Macs (via Rosetta).

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