formatting USB Flash memory for ubuntu ext4

I was having a similar problem. I resolved this by first unmounting the partition via cli:

sudo umount /dev/sdb1 (or whatever your usb is)

Then formatting the partition for ext4 (it cannot be formatted while mounted/in use):

sudo mkfs.ext4 /dev/sdb1

That should do the trick, worked for me.

One solution is to choose Format Disk and set it to no partitions. Then set the entire volume to ext4. Copy the tar file to the Flash device and use diff to verify.