Question

Hi,

I've used dd to clone hard drives before using 'dd' and a live cd, but have run into a problem.

The issue:

dd fails with an "Input/Output Error" on /dev/sda3 , even though windows "check disk" (chkdsk) says it's ok.

Context:

• Trying to replace my laptop hard drive w/ a faster one of the same size
• Laptop has NTFS on a 320gb hard drive
• Booting into knoppix
• Knoppix recognizes 'original' drive (/dev/sda)
• I am using a usb connection for ‘new' drive (irrelevant, but just an fyi)
• Knoppix recognizes the usb drive as /dev/sdb

• Using dd, as follows:

  dd if=/dev/sda of=/dev/sdb

• "dd" gives the I/O error above at 82Gb (out of 320Gb)

• I then tried checking each partition as follows and found it failed on /dev/sda3:

  dd if=/dev/sda1 of=/dev/null

  dd if=/dev/sda2 of=/dev/null

  dd if=/dev/sda3 of=/dev/null

• I have ran windows xp chkdsk on the offending drive in both "find only" and "find and fix" mode and it reports no errors

Question

How can I find and fix the error on my original hard drive partition (i.e. /dev/sda3) so that dd reads it successfully?

Answer 1

Use ddrescue for that, it's able to read damaged disks.

And chkdsk probably won't find the issue because it only does basic checks of filesystem integrity; by default, it won't check all the partition space for read errors caused by damage.