USB Unformatted when it was fine not 2 hours ago

[dalinux_n00bie]

So i plug in my thumb drive with nothing too important on it you know, just some finals that could mean the difference between a good grade or not, and i get a pop-up in windows that says "this drive is unformatted, do you wanna format it?" This scares me a lot. So i boot into linux and in "df -h", all it shows is "/dev/sdb", with no partitions on it.

I did some research, found this program called TestDisk. I ran the test and I got a "partition sector doesn't have the endmark 0xaa55" error.

Doing some more research, finding out that 0xaa55 is the last part of the boot sector, I told it to write to the MBR... the default....

How do i make it so that I can get my files? What causes this so i can avoid it?

[b2bwild]

You can back up the MBR and restore it when you want
to back it up

# dd if=/dev/sdX of=/home/foo/sda-mbr.bin bs=512 count=1

change X with applicable character.
change /home/foo with your home folder path
to restore it

# dd if=/home/foo/sda-mbr.bin of=/dev/sdX bs=1 count=64 skip=446 seek=446

EDIT:
Oh yeah, Its really hard to get the data back as you dont have the back up of your partition table.

[dalinux_n00bie]

EDIT:
Oh yeah, Its really hard to get the data back as you dont have the back up of your partition table.

So because i did the default "test write" of my MBR, and i don't have a backup of my partition table, i'm screwed...

[Jonathan183]

I suggest you backup the entire drive contents if you can ... that way you can restore it back to current state if needed. You can do this with dd but be careful about the order or you will wipe the drive !
What does

fdisk -l

report? are partitions recognised?

[dalinux_n00bie]

No it did not recognise any partitions. Both in fdisk and TestDisk.

[Jonathan183]

Can you post output of

fdisk -l

[dalinux_n00bie]

Can you post output of

fdisk -l

Partition table entries are not in disk order

Disk /dev/sdb: 8019 MB, 8019509248 bytes
247 heads, 62 sectors/track, 1022 cylinders
Units = cylinders of 15314 * 512 = 7840768 bytes
Disk identifier: 0x00000000

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb4               1        2192    16777216    0  Empty
Partition 4 has different physical/logical beginnings (non-Linux?):
     phys=(0, 0, 0) logical=(0, 0, 1)
Partition 4 has different physical/logical endings:
     phys=(0, 0, 0) logical=(2191, 23, 32)
Partition 4 does not end on cylinder boundary.

Disk /dev/sdb4: 17.1 GB, 17179869184 bytes
247 heads, 62 sectors/track, 2191 cylinders
Units = cylinders of 15314 * 512 = 7840768 bytes
Disk identifier: 0x00000000

     Device Boot      Start         End      Blocks   Id  System
/dev/sdb4p4               1        2192    16777216    0  Empty
Partition 4 does not end on cylinder boundary.

sorry for not doing this before. I was in windowz and had to boot into linux, and all the windows tools and some open source tools i found said there was no partition on it. BTW: this is a 8 gb flash drive, not a 17.1?

[dalinux_n00bie]

I also realized that this is in the network thread.... I could have sworn that i posted this in the Peripherals thread.....

[Jonathan183]

My suggestion is after you have backed up the whole drive use dd to wipe the MBR and re-run testdisk.

dd if=/dev/zero of=/dev/sdb bs=512 count=1

This should wipe the MBR including the partition table.

[dalinux_n00bie]

so how can i backup my drive if i can't access it?