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Recover a dead hard drive using dd
Authored by: burro on Mar 06, '05 12:44:58AM

I put mine in FW enclosure. It never mounts. Depending on the phase of the moon, the fire wire bridge chip will reported it as a unformatted drive or will refuse to work with the disk at all. In the latter there is no way you can use this scheme in ext. enclosures at least. Put it back in the original machine, boot it up from external and try again.

OS X will see the disk, mounted or not. Issue

disktool -l


With my failed FW enclosed drive hooked up I got two new entries

***Disk Appeared ('disk1',Mountpoint = '', fsType = '', volName = '')
***Disk Appeared ('disk0',Mountpoint = '', fsType = '', volName = '')

(for ref here is my bootup system disk mounted,
***Disk Appeared ('disk0s9',Mountpoint = '/', fsType = 'hfs', volName = 'System')

To decide which one is it (don't you hate UNIX for its unbelievable sloppiness?) go to Disk Utility, select your disk and using contextual menu (right mouse click) get Information. In my case FW enclosure was disk1.

Issue
dd bs=512 if=/dev/disk1 conv=noerror,sync | gzip -9 > foo.dmg.gz
to read that disk in. You should see some activity on that drive. Reading may take forever as internal disk microcode will try to read every failed block numerous times.



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How long will it take?!
Authored by: masthugget on Mar 07, '05 03:27:09PM

And with "forever" you mean?

I started a dd-session to make a disk image of my 60GB drive in my iBook and it has so far only copied 110MB in 85 minutes. At this speed it will take some 30 days to complete!

Can this be right?



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How long will it take?!
Authored by: electricferret on Mar 07, '05 04:41:24PM

Depending on the number and severity of errors on your disk, absolutely. 30 days might even be optimistic. In reality portions of your disk are probably still good and will read very quickly, but the errors slow the whole process down.

You might want to read the man page for dd, especially the "skip" and "count" options. Instead of reading the whole disk in one pass, you can read parts of the disk into several files and cat them together later. Of course this means you need twice the disk space of the original to reassemble the rescued image in.



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How long will it take?! / Done, but it won't mount!
Authored by: masthugget on Mar 08, '05 01:14:14PM

Just as you said, it was only certain parts of the drive that took that long, the rest went much quicker. It's ready now.

But now to another, more severe?, problem. I cant mount the .dmg file! When I try I get an error message saying that it can't connect to the filesystem (translation from swedish).

Any ideas?



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Recover a dead hard drive using dd
Authored by: DeminJanu on Jun 25, '09 05:44:02PM
btw, the terminal command df -k will list the UNIX device name along side the actual mount point (aka. the "real name" for us human beings). Of course the Root drive doesn't have a real name, it's just /
eg.
[me@mycomputer:[~]$] df -k
Filesystem 1024-blocks Used Available Capacity Mounted on
/dev/disk0s2 184408240 182249088 1903152 99% /
devfs 120 120 0 100% /dev
fdesc 1 1 0 100% /dev
/dev/disk0s3 10475512 577448 9898064 6% /Volumes/WINDOZE
map -hosts 0 0 0 100% /net
map auto_home 0 0 0 100% /home
/dev/disk2s3 312440112 287359576 25080536 92% /Volumes/Chronos
/dev/disk3s1 244136352 201556960 42579392 83% /Volumes/MELCHBACKUP
/dev/disk1s1 312492320 308901888 3590432 99% /Volumes/DEMBAK


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