help with dd command

[sudodus]

I suggest that you use gparted. It has an easy graphical user interface and lets you select size in Mibibyte units (2^20) bytes.

If you prefer a command line tool you can use parted (and use a separate tool to create the file system). Then you can select size more accurately, but you should be careful to match the start of a partition with the sectors of the drive.

Both tools work with MSDOS and GUID partition tables (GPT).

[1clue]

What dd will not do is copy a partition from one gpt drive over the top of the partition for another gpt drive. Each drive will have a unique UUID, and if the UUID is wrong then the partition table is corrupt. The UUID will NOT be the same between the two drives.

So your best bet is to create a (probably 20%) larger partition on the second drive, format it and then dd the first drive's partition over to a file on the second drive.

You can then use photorec on that file. If photorec needs the partition to be mounted you can mount it using -o loopback