First Aid is a utility included with the Macintosh operating system for checking and repairing file system errors. In Mac OS X, it is part of the Disk Utility program. In earlier versions of the Mac operating system, it is a separate program called Disk First Aid. It is a good idea to run First Aid or Disk First Aid once a month or so if you use your computer frequently to prevent major corruption to the files on your computer. You should also use First Aid/Disk First Aid if your computer system is crashing frequently. It will check for defects and, in many cases, repair them.

To check your startup disk-the disk you start up your computer with (usually your hard disk), you have to run First Aid or Disk First Aid from the system or installation disk, CD or DVD that came with your computer. If you are inserting a CD or DVD, while you restart your computer press and hold down the c key on your keyboard to force your computer to start up from the CD/DVD. Then open First Aid or Disk First Aid (see steps for OS X and earlier operating systems below). Use First Aid in OS X. The results of a verification and/or repair are displayed in the First Aid window.

You should run First Aid repeatedly until you see the following message at the end of the scan: 'The volume your disk name appears to be OK.' Sometimes, at the end of a scan, a message appears that says: 'Scan complete. Problems were found, but Disk First Aid cannot repair them.' In that case you can either check your back up copies of the affected files to see if they are okay and you can then replace the corrupted ones or you can try a commercial file repair or recovery program.

Disk Utility - First Aid - Repair Disk Permissions provides in red Error: The underlying task reported failure on exit' This was a nightmare for me to fix, but after I learned how it was easy. If you get this error and you have not already restarted your computer, open you sharing preferences and make sure you ahve not set the everyone group to 'no access'. If you have change it and retry to run the permissions repair. If you have already restarted you will need to startup using your install DVD and then open terminal.

In terminal type the following to fix your permissions. Chmod 775 /Volumes/'Macintosh HD' This will change your permissions and you should be able then to get past the grey screen.

Hope this helps someone. I'm too scared to turn my computer off now! However, I cannot find this 'everyone group' taht you speak of under 'sharing' in the system prefs. My iMac was running extremely slow.

I fixed the permissions, but when I went to verify disc, it came up with: Verifying volume “monster” Checking HFS Plus volume. Checking Extents Overflow file. Checking Catalog file. Invalid node structure The volume monster needs to be repaired. Error: The underlying task reported failure on exit 1 HFS volume checked Volume needs repair. So - i came hear, had a look around, and have the heeby jeebies scared into me.

So please - where may I find this 'everyone group'? Hi everyone, I believe my permissions are the problem. I let someone change permission settings to share music files on their hard drive and mine and another mac (3 in total) yesterday. I seemed to work. I can't remember if I then shut down my mac or just closed it. Anyway last night I was trying to organise the music files and burn them to dvd. I also tried change the permissions as some of the files were read only.

I though it worked. It seemed to be burning and the screen saver came up, I clicked to exit screen saver and it just went to black and back to screen saver and i couldn't go any further. I had to hold down the power button to turn if off. I tried to turn it on and now it's stuck on start up gray screen with the loading wheel thing?

Run First Aid From Recovery

Just loading forever. I used disk utility, verified volume and repair disk are ok, but verify permissions and repair permissions, I get an Error message 'the underlying task reported failure on exit' I opened terminal and typed in what tryjezus1 said,'chmod 775 /Volumes/'Macintosh HD' and pressed return. Not sure if I should have pressed return or if I should have just closed the window? Anyway I'm still stuck. I only have the mac since march so I believe I still have phone support, but if anyone can help I'd like to try and sort this out myself. Thanks, you saved my day (or maybe a couple of days).

Did something to some permissions apparently and that messed up my system, couldn't even get to the login screen. Managed to start up in Single user mode (Command-s after chime) but fsck did nothing for me. System seemed to be ok, or something like that it said, but still couldn't start up properly. Tried Repair Disk from Disk Utility on the Leopard DVD, that went through but couldn't Repair Permissions and still not boot & login. But this helped!

I gave the command chmod 775 /Volumes/'Macintosh HD' in Terminal as you said (starting up from the Leopard DVD). Then, using Disk Utility, I repaired permissions. And now my computer is back to normal. Of course, 'Macintosh HD' must be whatever your start up volume is called. Thanks again! Apple Footer.

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