[X-Unix] Running fsck on a target disk

[Eric F Crist]

Thom,

There is only one 'trick' to running fsck.  You need to define the  
mount point as one of the arguments, usually the last.  On a typical  
Mac system running Mac OS X, you could run fsck on the primary file  
system by running:

# fsck_hfs /dev/disk0s3

To run the above command on an HFS formatted file system, type:

# df -h

This allows you to find out where your disk is mounted.  When I  
connect a USB HFS formatted disk (an old startup volume, actually) I  
get:

Filesystem                Size   Used  Avail Capacity  Mounted on
/dev/disk0s3               93G    34G    58G    37%    /
devfs                     100K   100K     0B   100%    /dev
fdesc                     1.0K   1.0K     0B   100%    /dev
<volfs>                   512K   512K     0B   100%    /.vol
automount -nsl [201]        0B     0B     0B   100%    /Network
automount -fstab [205]      0B     0B     0B   100%    /automount/ 
Servers
automount -static [205]     0B     0B     0B   100%    /automount/static
/dev/disk1s3               74G    67G   7.2G    90%    /Volumes/ 
Macintosh HD 1

I can see that my new mount, Macintosh HD 1, is filesystem /dev/ 
disk1s3 which means, 2nd hard disk, slice 3.  Computers typically  
start counting from 0, so 1 is actually 2. ;)

Finally, to run fsck, we use Apple's fsck_hfs utility against the  
above listed filesystem, NOT the mount point, /Volumes/Macintosh HD 1.

# fsck_hfs /dev/disk1s3

I hope this helps!

-----
Eric F Crist
Secure Computing Networks