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List:       smartmontools-support
Subject:    [smartmontools-support]don't try this at home ... writing zeros back to error blocks with dd
From:       "Gary Funck" <gary () intrepid ! com>
Date:       2005-07-14 2:36:32
Message-ID: HLEPJEEBEKBMAHLBCNMMOEBACEAA.gary () intrepid ! com
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Got to thinking about recovering blocks that have uncorrectable errors,
with a few simple commands.  Here's an idea.  Assume /dev/hdc is the
drive with the UNC and it has a single partition /dev/hdc1.

first recover what we can:

e2fsck -c /dev/hdc1

Then read each sector back, and if it has an error write back a zero block

dd if=/dev/hdc of=/dev/hdc conv=noerror,sync bs=512

NOTE/WARNING: I DON'T KNOW IF THIS WORKS.  I HAVE NOT TRIED IT.
For discussion purposes only.

If I understand dd correctly, it will read a block from /dev/hdc and write
the same block back to /dev/hdc.  However, if it encounters an error,
it will write a zero block instead.

After this pass, I'd run e2fsck again:

e2fsck -c /dev/hdc1




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