2

user decided to reboot his pc during copy from usb stick and it corrupted his precious data. I'm trying to diagnose what's wrong but unfortunately i hit a wall and can't understand the issue with the stick.

I can see this disk in Disk Utility, but seems like all it has is unallocated space.

sudo fsck /dev/sdc
fsck from util-linux 2.27.1
e2fsck 1.42.13 (17-May-2015)
fsck.ext2: Attempt to read block from filesystem resulted in short read while trying to open /dev/sdc
Could this be a zero-length partition?

fdisk -l /dev/sdc
fdisk: cannot open /dev/sdc: Input/output error

Any help would be greatly appreciated.

dmesg /syslog:

[ 6073.351716] sd 6:0:0:0: [sdc] tag#0 Sense Key : Not Ready [current]
[ 6073.351719] sd 6:0:0:0: [sdc] tag#0 Add. Sense: Medium not present
[ 6073.351722] sd 6:0:0:0: [sdc] tag#0 CDB: Read(10) 28 00 00 76 c6 80 00 00 08 00
[ 6073.351724] blk_update_request: I/O error, dev sdc, sector 7784064
[ 6073.351726] Buffer I/O error on dev sdc, logical block 973008, async page read

He tried to copy around 500mb of work files from that stick, it froze and he rebooted "Just in case". As far I know that was the only copy of those files. Is there any way to try to restore data?

It's getting weirder and weirder. I gave up with restoring data and tried to wipe this stick with shred or dd. Outputs:

shred: /dev/sdd: error writing at offset 19218807296: Input/output error
shred: /dev/sdd: error writing at offset 19218807808: Input/output error

dd: error writing '/dev/sdc': Input/output error
1+0 records in
0+0 records out
0 bytes copied, 0,00123257 s, 0,0 kB/s

Tried to format on Win workstation, cant even plug it in or access through cli, got over hundred "Wrong folder name errors" in a few seconds.

Qqqq
  • 31

1 Answers1

0

Sounds like the drive's file structure was damaged. This can happen when the buffers are not completely written out to the drive before it gets unplugged.

In the future it helps to have pmount installed so the buffers are flushed properly during system idle time. It allows hot-plug-and-unplug gracefully.

To get it, 

sudo apt-get update
sudo apt-get install pmount

Another great feature of pmount is that the drive will retain its mount point. For instance, if it mounts as /media/me/USB32 but then is unplugged and replugged it will remount at that same location.

Without pmount the system will often not notice the dismount, or (as it sounds like in this case) will not have all the buffers written out to the drive (which can include directories).

If it does not notice the dismount then it is likely to append a digit to the remounted USB stick, resulting in `/media/me/USB321' - which means that if you write to the original address the system will treat it as a directory on the root partition. The contents will never reach the USB stick in that scenario.

I consider pmount to be a MUST-HAVE. Then gone are the days of needing to type sync;sync;sync when using these drives.

SDsolar
  • 3,219