dd: The Dying Disk's Best Friend

If you’ve ever had a hard drive die, whether slowly or spontaneously, you know the horror of thinking about how you’re actually going to restore all those backups – you DO take backups, right? I don’t for a lot of my personal stuff, knowing full well that I might end up in the same situation that a friend called me about today. His hard drive started making the patented Click of Death sound, the obvious symptom of a near-dead hard drive.

We managed to save the majority of his files by plugging the disk into my linux box, but not mounting it as a filesystem. Instead, using the handy unix tool dd to copy the raw contents of the disk to a file:

dd if=/dev/sdd of=/home/dave/deadhd.bin conv=noerror,sync

This command reads the contents of the device /dev/sdd and outputs it to /home/dave/deadhd.bin. The conv options specify that dd should ignore read errors (which are likely to occur while reading a dying disk), and to synchronize the read position with the write position when those errors occur. The file deadhd.bin could now be mounted:

mount -o loop -t ntfs /home/dave/deadhd.bin /mnt/deadhd

/mnt/deadhd is now ready to be explored. There are bound to be files which can’t be read, but hopefully many can be copied out and recovered. See, we don’t need backups anyway! (/sarcasm)