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I'm looking for the CLI equivalent of "Check disk" and "repair disk" in Disk Utility. I think fsck is involved but I don't know with which options, and if it's the only program run.

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2 Answers 2

up vote 5 down vote accepted

In fact, Disk Utility does use fsck to check the disk in question. "Verify Disk" uses

 /sbin/fsck_hfs -fn -x /dev/diskX

while "Repair Disk" runs

/sbin/fsck_hfs -fy -x /dev/diskX

These are the options used:

-f: 'f'orces a check, even if the disk seems to be clean

-n: 'n'ever attempts to repair any found issues

-y: says 'y'es to any question whether an issues should be repaired (as you might have guessed, -n and -y are exact opposites)

-x: generates output in XML format, which is parsed by Disk Utility

/sbin/fsck (as opposed to /sbin/fsck_hfs) is a wrapper that calls /sbin/fsck_XXX for the type of file system in question. You'll get more information in the man pages for fsck and fsck_hfs, from which I've borrowed a lot of information for my reply.

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Hum, it seems that the disk utility is doing much more than the single fsck_hfs -fy. The former worked, while the latter failed with the message 'Disk reparation faild. Aborting.'. –  gregseth Sep 5 '11 at 21:20
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/usr/sbin/diskutil is what you are looking for.

Checkout man diskutil and look at the repairVolume command.

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The advantage of using diskutil over fsck_hfs, is that where for example $ fsck_hfs -fy /dev/disk1s2 might not fix errors found "** Cannot repair volume when it is mounted with write access. ** The volume Backup could not be repaired.", where $ diskutil repairVolume /Volumes/Backup unmounts the Volume and fixes the problems found. –  Pro Backup Jun 24 '12 at 11:30
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