reasons to run fsk-y

[csonni]

I've never had a reason to run this command yet.  Other than Repairing Permissions, is there a need to run fsk-y in the Terminal?  Doesn't the Disk Utility do the same thing (when booted off of another drive)?

[CyberPet]

Yes, when you boot from your CD and run Disk Utility it does the same thing (i.e. checking the harddisk), however you might not always have your CD handy, when you're out traveling with your laptop etc. Then running fsck -y in Single User mode is a good idea. However as well as Disk Utility cannot fix everything, neither can fsck -y, so always have another disk utility software (such as Diskwarrior) handy.

[kps]

fsck needs to run in Single User Mode (command+s) and not in the terminal application while the whole system is up.

It checks and repairs file system consistency and does not repair disks in the same manner as DiskWarrior.

[tacit]

When your disks are formatted using HFS+ (MacOS Extended), which is the norm for OS X systems, it's important to note that fsck uses the Disk First Aid libraries.

In English, what that means is that on computers using HFS+ disks, running Disk First Aid is exactly the same as using fsck. fsck works precisely the same way, but without a graphical user interface.

MacOS X lets you format disks in two ways: As HFS+ (MacOS Extended), or as UFS (Universal File System). 99.999% of all Macs are using HFS+, because if you format your disks using UFS, you can't run regular Mac applications and you can't run Classic. The only reason you would ever use UFS on an OS X system is if you are using the computer as a file and/or Web server and you don't need to run regular Mac programs.

If your disks are formatted using UFS, then fsck runs the regular BSD filesystem check. If your disks are formatted with MacOS Extended, then fsck just runs Disk First Aid with no graphical user interface; it does not run BSD fsck.

So for the most part, there is little reason to run fsck. Disk First Aid is capable of doing everything fsck does.

It's a good idea to buy a third-party disk repair program like DiskWarrior. Programs like DiskWarrior are more sophisticated than Disk First Aid,and can fix problems Disk First Aid can't.