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Old 09-11-2015, 11:58 PM   #1
mazinoz
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fdisk a drive that has been completely written over including mbr


I overwrote an external drive completely with

dd if/dev/urandom of=/dev/sdb

In the past I think I partitioned it with fdisk, format or with gparted.

Now however, neither W7 or linux recognises the device. Same problem with a USB stick.

Any help to get these devices partitioned appreciated.
 
Old 09-12-2015, 12:05 AM   #2
unSpawn
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In short you've destroyed its contents completely.
So you start at partitioning the device using fdisk or any tool you like to use.
Seen http://tldp.org/HOWTO/Partition/fdisk_partitioning.html ?
 
Old 09-12-2015, 12:54 AM   #3
syg00
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I think the OP has tried - it used to be fdisk was pretty dumb and would work fine after zapping the disk. Now it does a lot more checks - some of which may get in the way.
Maybe try a parted script to write a partition table.
 
Old 09-12-2015, 07:02 AM   #4
jpollard
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Ah. I think this happens because fdisk believes the disk has real data rather than random data.

Try "dd if=/dev/zero of=/dev/<whatever the disk is> bs=1M count=1". This should zero the first 1 MB of the disk (where the partition table would be, as well as any data in the first partition).

I had this problem after a hardware raid initialised some disks for itself. When I tried to use the disk without the controller fdisk wouldn't process the disk. Zeroing the beginning of the disk allowed things to work.
 
Old 09-12-2015, 04:33 PM   #5
tredegar
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Quote:
Now however, neither W7 or linux recognises the device. Same problem with a USB stick.
Would this be a USB connected device?

Maybe the problem lies with the USB port or cable?

Time for some experiments, I think. Try with a different computer, and /or a different USB cable.
 
Old 09-12-2015, 08:06 PM   #6
sgosnell
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What do you mean by won't recognize the disk? Have you tried gparted on it? You should be able to use it to add a new partition table and filesystem to the drive.
 
Old 09-12-2015, 11:28 PM   #7
mazinoz
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One device is an external drive connected via USB to laptop, the other a USB stick. If I do lsusb neither is found. Gparted doesn't show up anything other than the laptop hard drive. After doing overwriting I rebooted using a clean Linux Mint 17.2 disk before partitioning either external drive or USB stick. I've managed in the past to partition or load a filesystem onto USB stick and drive but have forgotten how I did it.
 
Old 09-12-2015, 11:32 PM   #8
mazinoz
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I've just logged in. I think it was parted I used, will report back after I have tried that.

Thanks everyone.
 
Old 09-18-2015, 12:19 PM   #9
ondoho
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Quote:
Originally Posted by mazinoz View Post
If I do lsusb neither is found. Gparted doesn't show up anything other than the laptop hard drive.
afaiu, your problem is to find the drive, so that you can perform the dd thing described in post #4 (which i can confirm has helped me, too, in similar cases).
several ways:
- type "dmesg" in a terminal. have a good look at the last lines.
- plug in the drive. wait a minute.
- type "dmesg" again. look at the new lines. chances are it will tell you something about a new device, and where it resides (most probably /dev/sdXX).

you can do something very similar with "ls /dev".

you can also try "sudo fdisk -l".
 
Old 09-20-2015, 08:29 PM   #10
mazinoz
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Thank you everyone for your help,and my delay in replying to last post here. This is so embarrassing. I tried dmesg with and without the cable plugged in. Same message each time. I then tried to use a different cable with the external hard drive but the manufacturer in their wisdom made the drive plug so it only fits their cable. So I reinserted their cable and the device lit up and was found! I haven't had any issues in the past like this. First time I used dd on this drive so thought it was that. Now I have an external Backup drive, such a relief. Once again thank you.
 
  


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