[Bug-ddrescue] ddrescue trashed partition table (invalid args not trapped)

[Russell Odom]

Hi,

I was trying to clone a failing disk (sda) to a new one (sdb), using the 
command line...
ddrescue -f -n1 /dev/sda /dev/sdb mapfile
...following the example at 
https://www.gnu.org/software/ddrescue/manual/ddrescue_manual.html#Examples .

I was somewhat surprised to find that ddrescue had
* read from sdb
* written the data from sdb to mapfile, stopping only when the partition was 
full (3.9GB)
* written its mapfile to sda - overwriting the first 7179 bytes of the device, 
thus destroying the partition table and the first ~6MB of the data in the first 
partition (which happened to be /boot)

Fortunately I had taken a dump of "fdisk -l /dev/sda" and was able to manually 
restore the partition table by hand (a hairy experience), but the damage to 
/boot was such that the OS was rendered unbootable (the other 2 partitions on 
the drive were OK). I checked "ddrescue --help" and confirmed I had the 
source/dest/mapfile arguments in the right order, and I had a colleague confirm 
it too. However, on re-reading very carefully I see I put "-n1" instead of "-n" 
- this appears to be invalid argument, but ddrescue continued anyway and the 
results were obviously fairly disastrous.

This is with ddrescue 1.18.1 as included on SystemRescueCd-x86-4.7.1 
(http://www.system-rescue-cd.org/).

Let me know if I can provide any more info.

Regards,

Russ

--
Russell Odom
Technical Lead

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