The partition table is still in memory so you will have some luck till you reboot or force the system to do a partprobe.

The following link points to how to recover your partition from the in system data:
http://unix.stackexchange.com/questions/43922/how-to-read-the-in-memory-kernel-partition-table-of-dev-sda

That being said first you should  back up all the data you can to an external drive
If your going to play with testdisk then it is best to learn on an image of the broken drive so copy the whole drive off to some other system to play with.

I have trashed enough systems in my time to know that a good backup is the best way to insure that things go well.



On 10/25/2016 07:33 AM, Matt Price via talk wrote:
OK, so I did this

dd if=some.iso of=/dev/sdb

oops -- that's not the USB key! that's my internal m.2 drive!

The partition table is gone, but it used to contain 2 partitions, both of them in an LVM, one of them part of an extended logical volume that added space to /home on my overburdened main drive. I haven't lost much data (just the first 700mb were overwritten), and amazingly my laptop continues to run just fine -- even though lvscan reports a missing drive, apparently the data is still findable. 

I'd like to restore the partition table but I don't know where the partition boundaries are, and in any case I don't know how to write a partition table (!). What tools should I use? Preferably without turning off my laptop, since I'm afraid it won't boot back up again!


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