EFI system

How to use TestDisk to recover lost partition
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Joined: 08 Sep 2017, 04:33

EFI system

#1 Post by bdalzell »

I am trying to repair a 1 TB harddrive. Testdisk reports the following partition structure:
Disk /dev/sde - 1000 GB / 931 GiB - CHS 121601 255 63
Current partition structure:
Partition Start End Size in sectors

Trying alternate GPT
1 P Unknown 2048 2097151 2095104 [Basic data partition]
2 P EFI System 2097152 2834431 737280 [EFI system partition]
No FAT, NTFS, ext2, JFS, Reiser, cramfs or XFS marker
3 P MS Reserved 2834432 3096575 262144 [Microsoft reserved]
3 P MS Reserved 2834432 3096575 262144 [Microsoft reserved]
4 P MS Data 3096576 1934422015 1931325440 [Basic data partition]
5 P MS Data 1934424064 1953509375 19085312 [Basic data partition]

>[Quick Search] option is currently highlighted.

Running testdisk under Ubuntu linux on a damaged drive that is mounted as an additional drive on my computer.
It has been running the Quick Search for quite a while with nothing happening except for the drive light being on.

Following the instructions it seems to me that partition 3 is damaged as it appears twice in the list.

Does testdisk work on EFI partitioned drives? Does it recognize the MS Data partitions?
How long should I expect testdisk to run before the next stage in the recovery appears?

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Re: EFI system

#2 Post by cgrenier »

From testdisk reports, it looks like your EFI partition table is corrupted.
On next screen, use 'a' to manually add the partition 3 (use the same start/end values). Next, choose Write, confirm, Quit and restart your computer.

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Joined: 04 Oct 2017, 16:47

Re: EFI system

#3 Post by Ammarti850 »

I know I'm a month late for this reply, but I thought I'd share my 2 cents.

Running TestDisk on my x64, UEFI laptop with a 750GB Toshiba HDD (512e, 4k Advanced Formatting) defaults to 512n (legacy size) byte physical sectors rather than 4096K physical sectors with 512 logical. Being that the program is more than likely written for compatibility across multiple platforms and architectures, it doesn't surprise me that much.

The issue isn't necessarily EFI, but the GPT (GUID partition table) partitioning method. Older MBR (Master Boot Record) drives still depend on the BIOS to get the bootloader info, while GPT stores the bootloader and kernel in the EFI System Partition. But...everything is dependent on the disk ID, so recovering partitions may not be much help if the disk was cleaned. I personally don't like EFI, only because I haven't worked with it enough and it's the sole reason I have to try to recover an entire disk after an emergency install of Windows 7 - which does not support installing on GPT disks OR USB drives.

If you try to repair it after recovery, I highly recommend reading up on GRUB/GRUB2, DISM.exe, bcdedit.exe, SDI and BCD files, and WIM images. I'm kicking myself after trial and error.