There is an I/O error in the hard disk in my MacBook Pro running Mountain Lion and as I start it up, a progress bar fills up and then it shuts down on its own. I attempted to recover the files in single-user mode and try to fix it by rebuilding the catalog btree as in this answer:

fsck_hfs -Rc -d /dev/disk0s2

Unfortunately it encountered numerous errors as it approached the part with a disk error. Since then the Macintosh HD does not mount in single-user mode and I am only left with the Mac OS X Base System.

Running df -hl on the 500GB drive gives the following:

Filesystem    Size   Used  Avail Capacity iused ifree %iused  Mounted on
root_device  1.2Gi  1.1Gi  106Mi    92%  280978 27978   91%   /

of which 1.2GB represents the Mac OS X Base System.

fsck_hfs -l /dev/disk0s2 gives:

** Checking catalog file.
   Missing thread record (id = 18)
   File record has hard link chain flag (id = 38468309)
   File has incorrect number of links (id = 38468309)
   (It should be 1 instead of 2)
   Missing thread record (id = 216712)
   Incorrect number of thread records
(4, 202)
   Incorrect number of thread records
(4, 202)
** Checking multi-linked files.
   Incorrect number of file hard links
** Checking catalog hierarchy.
** The volume   could not be verified completely.

And /sbin/fsck/ -fy gives:

** The volume Mac OS X Base System appears to be OK.

I tried to manually mount the drive with

mount -t hfs /dev/disk0s2 "/Volumes/Macintosh HD"

but it didn't work:

hfs_mounts: failed to mount non-root inconsistent disk
hfs_mount: hfs_mountfs returned 22
mount_hfs: Invalid argument

How do I correctly rebuild the catalog btree and remount disk0s2 (which is the Macintosh HD)?

  • Some might be in /lost+found
    – mmmmmm
    May 15, 2013 at 16:08
  • @Mark Where do I find this? cd: /lost+found: No such file or directory
    – AppleBoy
    May 15, 2013 at 16:11
  • If fsck does find things iy puts them in that dir. If the directory is not there nothing was found
    – mmmmmm
    May 15, 2013 at 16:15
  • AppleBoy, what have you done this time :(
    – Ruskes
    May 15, 2013 at 18:35
  • @Buscar웃 I checked again carefully and discovered that I didn't just lose /Users, the whole Macintosh HD was gone. Attempting to mount manually would give errors like failed to mount non-root inconsistent disk and hfs_mountfs returned 22.
    – AppleBoy
    May 15, 2013 at 18:42


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