hfsdebug iconhfsdebug 4.33

A read-only debugger for HFS Plus file system volumes
hfsdebug is a filesystem debugger for Apple's HFS Plus 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.

Therefore, 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 inspect, browse, and analyze various aspects of HFS+ volumes. It can also calculate and display certain filesystem statistics.

hfsdebug supports only the HFS+ volume format. The older HFS format is not supported. It does, however, support the following HFS+ variants:
· HFS Plus
· Journaled HFS Plus
· HFS Plus (journaled or otherwise) embedded within an HFS wrapper

Note that hfsdebug should work with HFS+ volumes regardless of whether they reside on a real, physical disk (or disk slice), or on a "virtual" disk (such as a disk image).

Main features:

  • View the Volume Header and the Master Directory Block (in case of "embedded" HFS+ volumes).
  • View contents of the header nodes of HFS+ "special files". These files include the Catalog, Overflow Extents, and Hot Files B-Trees.
  • List and view details of one or more types of records contained in the special file B-trees, such as:
  • File records, file thread records, folder records, and folder thread records (the Catalog B-Tree).
  • Extent records (the Extents Overflow B-Tree).
  • Hot file records and hot file thread records (the Hot File Clustering B-Tree).
  • View detailed information about filesystem objects, such as files, folders, aliases, symbolic links, and hard links. An object may be looked up using its Catalog Node ID (typically, but not always, the same as the inode number reported by the POSIX API), a Carbon style specification (the object's "node name" and the Catalog Node ID of its parent), or using its POSIX path.
  • View detailed information contained in a volume's journal, if any.
  • Calculate and display volume statistics, such as:
  • Top N files ordered by size.
  • Top N files ordered by their degree of fragmentation.
  • Top N files ordered by how "hot" they are (in the context of Hot File Clustering).
  • A summary of the number of various kinds of filesystem objects present on a volume, their space usage, special cases such as invisible and empty files, and so on.
  • Display details of all fragmented files on a volume.
  • Display location and size of all free extents on a volume.

last updated on:
February 12th, 2010, 6:29 GMT
file size:
62 KB
developed by:
Amit Singh
license type:
operating system(s):
Mac OS X 10.4 or later
binary format:
Home \ System Utilities


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2 Screenshots
hfsdebug - This is hfsdebug running in a Terminal window on Mac OS X.hfsdebug - This is hfsdebug's help message displayed when running the tool using the "-h" argument.

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