[nmglug] Check a disk?

[Nick Frost]

On 03/25/2013 05:34 PM, Nick Frost wrote:
> As long as you are not booting from the suspect drive it does not
> matter. It likely has an ext3 filesystem and ext3 is ext3..the data
> should be readable you just can run 64-bit Linux binaries on a 32-bit
> system.  Same applies with ext4.

So much for my proofreading skills, the above was supposed to say "you
just *can't* run 64-bit binaries on a 32-bit system"

John's better suggestion of running ddrescue on the partition rather
than the drive makes more sense, fewer sectors for ddrescue to read
(less wear on the disk) and no offset to deal with.

I'll second Bob's excellent point on patience. I was given six drives
last Summer by an individual that had been stored in a cardboard
box..one being a scuffed-up 2.5" laptop IDE drive that yielded something
like a 96.64% recovery after ddrescue ran for something like 4-5 days.

In terms of diagnosis as to whether the issue is logical (file system
damage) or hardware you could run "smartctl -H /dev/sdb" or "smartctl -t
short /dev/sdb", "smartctl -t long /dev/sdb" but I would make the image
first, try to mount it and only resort to determining the cause of
failure after the recovery. The idea is....if the drive has "grown" bad
sectors or incipient mechanical failure to image the drive before it
gets any further unnecessary requests for sector reads.  If the imaged
partition & file system is not mountable you could use a hex editor to
have a look for data.

There are also some affordable commercial tools, some for Linux like
R-Studio;

http://www.r-tt.com/BuyOnLine.shtml

that may be worth trying if other methods fail.  Testdisk (free) by
Christophe Grenier (CG Security I think) and other programs can
sometimes recover files without looking at the file system; however in
some cases while files are recovered file names may not be presenting
the tedious data housekeeping task of renaming what is recovered.  I've
used Testdisk with good results but haven't tried R-Studio so can't
comment on that.

-N

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Nicholas S. Frost
7 Avenida Vista Grande #325
Santa Fe, NM  87508
nickf at frostitute.com
http://www.datamender.com/
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