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So, I recently installed Ubuntu on my old laptop after using Windows 10. I was using an external HardDrive (Seagate Backup Portable 4TB - formatted as NTFS) on windows, that I started using on Ubuntu. When I opened GParted, I was given the message:

The backup GPT table is corrupt, but the primary appears OK, so that will be used.

I found some answers (1) that had some similarities to my issue and I tried them but didn't work.

Here is the result of sudo sfdisk -l /dev/sdb

The backup GPT table is corrupt, but the primary appears OK, so that will be used.
Disk /dev/sdb: 3,65 TiB, 4000787029504 bytes, 7814037167 sectors
Disk model: BUP BK          
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: F33087C3-E03F-4A5A-A52A-2D5C30471082

Device      Start        End    Sectors  Size Type
/dev/sdb1      34     262177     262144  128M Microsoft reserved
/dev/sdb2  264192 7814035455 7813771264  3,7T Microsoft basic data

Partition 1 does not start on physical sector boundary.

and the result of gdisk p command:

Disk /dev/sdb: 7814037167 sectors, 3.6 TiB
Model: BUP BK          
Sector size (logical/physical): 512/4096 bytes
Disk identifier (GUID): F33087C3-E03F-4A5A-A52A-2D5C30471082
Partition table holds up to 128 entries
Main partition table begins at sector 2 and ends at sector 33
First usable sector is 34, last usable sector is 7814037133
Partitions will be aligned on 8-sector boundaries
Total free space is 3692 sectors (1.8 MiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1              34          262177   128.0 MiB   0C01  Microsoft reserved ...
   2          264192      7814035455   3.6 TiB     0700  Basic data partition

I tried the following:

  1. sudo gdisk /dev/sdb followed by the v command which resulted in the following:
Command (? for help): v

Problem: The secondary header's self-pointer indicates that it doesn't reside
at the end of the disk. If you've added a disk to a RAID array, use the 'e'
option on the experts' menu to adjust the secondary header's and partition
table's locations.

Problem: main GPT header's current LBA pointer (1) doesn't
match the backup GPT header's alternate LBA pointer(7814037166).

Problem: main GPT header's backup LBA pointer (7814037166) doesn't
match the backup GPT header's current LBA pointer (1).
The 'e' option on the experts' menu may fix this problem.

Problem: The backup partition table overlaps the backup header.
Using 'e' on the experts' menu may fix this problem.

Caution: Partition 1 doesn't begin on a 8-sector boundary. This may
result in degraded performance on some modern (2009 and later) hard disks.

Consult http://www.ibm.com/developerworks/linux/library/l-4kb-sector-disks/
for information on disk alignment.

Identified 4 problems!
  1. I used gdisk e command as instructed to try and fix that, but when I close and open gdisk and enter the v command I get the same result.

  2. I tried to write (w) the table to the disk, but that also didn't work.

  3. I ran the disk error checking option (in the harddrive properties) in Windows 10 and it resulted in no errors.

I am a little lost as to what do, any help would be greatly appreciated.

PS: I am new to Linux so bear with me :), and let me know if any other info is needed.

Edit1: As per the comment by @oldfred , I performed the following gdisk commands on the drive (x -> e -> w) and restarted the pc. Now the

The backup GPT table is corrupt....

message doesn't show on sfdisk -l and 3 of the problems shown by gdisk' v command are gone, but when I open GParted, I still get the

The backup GPT table is corrupt....

message.
Result of sudo sfdisk -l /dev/sdb

Disk /dev/sdb: 3,65 TiB, 4000787029504 bytes, 7814037167 sectors
Disk model: BUP BK          
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: F33087C3-E03F-4A5A-A52A-2D5C30471082

Device      Start        End    Sectors  Size Type
/dev/sdb1      34     262177     262144  128M Microsoft reserved
/dev/sdb2  264192 7814035455 7813771264  3,7T Microsoft basic data

Partition 1 does not start on physical sector boundary.

Result of gdisk v command

Problem: main GPT header's current LBA pointer (1) doesn't
match the backup GPT header's alternate LBA pointer(7814037166).

Caution: Partition 1 doesn't begin on a 8-sector boundary. This may
result in degraded performance on some modern (2009 and later) hard disks.

Consult http://www.ibm.com/developerworks/linux/library/l-4kb-sector-disks/
for information on disk alignment.

Identified 1 problems!
4
  • Should be: To move backup to end of drive launch gdisk, then type x, then type e, then type w to save your changes, if you exit before saving then it is not updated. rodsbooks.com/gdisk/repairing.html
    – oldfred
    Jul 23, 2020 at 14:59
  • ok, so when I saved after using the e command the list of problems were reduced to 1 (I added it to an edit in the original post since its too big for a comment). Now the drive doesn't show the "The backup GPT table is corrupt..." message in sfdisk -l or gdisk but it still shows when I open GParted.
    – Adam
    Jul 23, 2020 at 15:34
  • It looks like you used Windows to create gpt. It always adds the Microsoft reserved as Windows requires that before any Windows install. If not installing Windows on that drive, you can delete it. But with newer 4K drives you have to have partitions aligned correctly. By author of gdisk: developer.ibm.com/tutorials/l-linux-on-4kb-sector-disks I thought all partitioning tools both Windows & Linux aligned partitions correctly or did you override defaults? Post on 8-sector boundaries alignment by srs5694 ubuntuforums.org/showthread.php?t=1685666
    – oldfred
    Jul 23, 2020 at 16:08
  • I don't remember the details as I never formatted the drive since I got in in 2015. If I formatted the drive after buying it, it would have been to change the file system to NTFS, but I would have used the defaults (I was using windows 10 back then) as I don't know much about drives in general.
    – Adam
    Jul 23, 2020 at 16:45

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