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Ask Max: Overlapped extent allocations

Asked on 11/14/2007:

I've had my new MacBook for about 3 months now, and for the 2nd time, I've been unable to boot it up due to overlapped extent allocations. I know this because I can boot into single-user mode and run FSCK, which returns the list of culprits as it repairs them. I've seen lots of info online about how to fix this, but nothing about what causes it. Any insight?

Do you think I should reformat the entire drive, or just do an archive and install? I'm afraid that if I keep going without doing either, I will eventually overlap a critical system file, and I won't be as lucky as I have been the first two times the problem occurred.

Risking it all in PA....


The cause of the problem may be hard to pin down but here is something to try. You can take the identifier number that is reported by FSCK and track down the affected files. When you run fsck, it should report both the inode number of the file, and its name. If the inode number is nnnnn, follow these steps to get the pathname to the file:

Open Terminal, located in /Applications/Utilities.


sudo -s

Press Return and you will be prompted for your administrative password, the one you chose when you installed Mac OS X.


find / -inum nnnnn -print

Replacing "nnnnn" with the inode number and if the reported inode number has a letter at the end, only use the numbers.

This should give you the path to the affected files. If all the files are associated with the same function of your Mac (i.e. all Safari Cache files), then you can assume that it is related to a bug in that application. If you find that they are all random files, then I would have you completely erase your drive.

If you have an external drive that will fit the full contents of your drive, I would recommend using Carbon Copy Cloner to backup your entire drive.

After you have an exact copy of your drive, insert the grey restore DVD that came with your Mac. Restart your computer and hold down the "C" key to boot up from that disc. Once booted from the Disc, go to the Utilities menu and select Disk Utility. Now select your internal hard drive and go to the Erase tab. Click on the Security Options button and then select the option to write zeros over the drive. One pass will do, because you are just trying to make sure that the drive is in good condition. This could take many hours so don't be in a rush when you start this process.

After it is done writing zeros you should do one more step. Click on the Partition tab. You must have the internal hard drive, and not the volume, selected in the left column for the Partition tab to be visible. Change the Volume Scheme popup menu from "Current" to "1 Partition." Next click on the Partition button. With all this drive formatting work done you can quit Disk Utility and install a clean copy of OS X 10.4 on your Mac. Once the installation is done, start moving through the setup screens. When you are asked if you want to move files over from another Mac, answer yes and connect the external drive you cloned your old System onto. It will treat that like an old Mac and move over all your important files and applications.

That should fix your drive problems if it was a formatting error. If you still have problems after doing all of the above, then it may be a hardware problem. An Apple Authorized service center can help you if it is hardware related.

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