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I have tried everything, but nothing works...

Background: Started out with Windows 7, formated and installed Ubuntu and later installed Arch linux with a GPT partition table.

Running following commands from Ubuntu 12.04 Live USB.

Starting with: Have Arch Linux installed with four partitions. Using GPT.

/dev/sda1 Root partition
/dev/sda2 BIOS boot partition
/dev/sda3 Swap partition
/dev/sda4 /home partition

Step 1:

sudo parted /dev/sda
mklabel msdos

Get the "GPT signatures found"-error message then I check.

Step 2:

sudo dd bs=4M if=/dev/zero of=/dev/sda

Still get the error message.

Step 3:

sudo dd bs=1M if=/dev/zero of=/dev/sda

Still get the damned error message about GPT signatures found.

Step 4>

sudo parted /dev/sda
mktable msdos

I'm not giving up! Even this doesn't work, and the error message appear.

Output from sudo fdisk -l:

Disk /dev/sda: 250.1 GB, 250059350016 bytes

255 heads, 63 sectors/track, 30401 cylinders, total 488397168 sectors

Units = sectors of 1 * 512 = 512 bytes

Sector size (logical/physical): 512 bytes / 4096 bytes

I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk identifier: 0x0004cb5a

Device Boot Start End Blocks Id System

WARNING: GPT (GUID Partition Table) detected on '/dev/sdb'! The util fdisk doesn't support GPT. Use GNU Parted.

Disk /dev/sdb: 2103 MB, 2103443456 bytes

255 heads, 63 sectors/track, 255 cylinders, total 4108288 sectors

Units = sectors of 1 * 512 = 512 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk identifier: 0x71bafca0

Device Boot Start End Blocks Id System

/dev/sdb1 * 0 1607679 803840 0 Empty

/dev/sdb2 1595952 1600495 2272 ef EFI (FAT-12/16/32)

WARNING: GPT (GUID Partition Table) detected on '/dev/sdb1'! The util fdisk doesn't support GPT. Use GNU Parted.

Disk /dev/sdb1: 823 MB, 823132160 bytes

255 heads, 63 sectors/track, 100 cylinders, total 1607680 sectors

Units = sectors of 1 * 512 = 512 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk identifier: 0x71bafca0

 Device Boot      Start         End      Blocks   Id  System

/dev/sdb1p1 * 0 1607679 803840 0 Empty

/dev/sdb1p2 1595952 1600495 2272 ef EFI (FAT-12/16/32)

Output from sudo parted -l

Model: ATA ST250LT007-9ZV14 (scsi)

Disk /dev/sda: 250GB

Sector size (logical/physical): 512B/4096B

Partition table: msdos

Number Start End Size Type File system Flags

[GPT-Signatures-found error message]

What should I do to remove the last fragments of the GPT table? Trying to reinstall Arch again, but can't use cgdisk to create partitions.

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Did the dd give an error? or do you mean it did not make the error go away? –  richard Aug 18 '13 at 21:33
    
The dd command didn't output any error message. –  user152158 Aug 18 '13 at 21:42
    
According to wikipedia GPT stores another copy of its data at the other end of the disk, therefore do another dd with an offset to take-out, the last few blocks of the disk. –  richard Aug 18 '13 at 22:00
    
What error message? Don't substitute your own words; paste the actual error. –  psusi Aug 19 '13 at 1:30

1 Answer 1

up vote 1 down vote accepted

Your fdisk and parted outputs both indicate that you've got two disks: /dev/sda and /dev/sdb. The "GPT data" error seems to be coming from /dev/sdb. I recommend running FixParts on this disk. This program is part of the gdisk package, which you may need to install. If it detects stray GPT data, it will ask you if you want to remove it. You can then exit from FixParts without making any more changes. You can also try running FixParts on /dev/sda, but I suspect it's completely clean of stray GPT data.

Incidentally, Richard is correct about GPT storing a second copy of its data at the end of the disk; but given the steps you've taken and the output you've shown, I don't think you're seeing the effects of that data on /dev/sda; I think you're seeing stray GPT data in sectors 1-33 (and probably at the end of the disk) on /dev/sdb.

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