A drive with 2 partitions - 1st is plain ext4, second is encrypted LUKS. The partition table has been overwritten. I've found the beginning of the second partition , which i need to recover, thusly:

#hexdump -s 400000m -C /dev/sdc | grep LUKS
61d3dec850 79 c8 81 6d e5 4c 55 4b 53 40 49 aa 29 df de d7 |y..m.LUKS@I.)...|


#losetup -o 0x61d3dec850 -r -f /dev/sdc
#losetup -a
/dev/loop0: [0005]:477209 (/dev/sdc), offset 420166420560

ok so far, then this problem pops up:

#cryptsetup luksOpen /dev/loop0 luksrecover
Device /dev/loop0 is not a valid LUKS device.

Please advice how to proceed. Is it wrong offset? Should I seek for the magic number 0xEF53 identifying ext4 as adviced here https://unix.stackexchange.com/questions/103919/how-do-i-find-the-offset-of-an-ext4-filesystem ?

Mind you it's a 1TB drive so please I need an advice that does not force to scan the entire drive ( hours and hours) all over again if possible, such as testdisk which seems have no option to start at a specified offset to save time on scanning. Thanx in advance.

P.S. This was close , but not quite: https://unix.stackexchange.com/questions/177070/lvm-encrypted-partition-without-partition-table


I'm affraid you didn't find the correct offset of the LUKS partition. After LUKS should appear \xba\xbe and, in your hexdump, it is not so.

Try searching the disk with LC_ALL=C grep -a -b -P 'LUKS\xba\xbe' /dev/sdc

If the partition data is still there, the output will be: offset:LUKS.... with the correct offset (decimal) you should use.

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