How to make a bootable iso from a flash drive on linux?

Question

linux

It seems that I used to create a bootable iso in this way:
dd if=/dev/cdrom of=~/cd.iso
Here, instead of a cdrom flash drive, I try:
dd if=/dev/sdb1 of=~/cd.iso
And I get an I/O error.
Perhaps this is due to the fact that I have a flash drive and not cdroom, or because the flash drive has a windows distribution and not linux. How else can you create a bootable iso from a flash drive?
The problem turned out to be a corrupted flash drive.

Answer 1

https://www.cyberciti.biz/faq/howto-copy-mbr/
They still need dances with a tambourine

Answer 2

ubuntu make bootable usb from iso

Answer 3

maybe it's /dev/sdb instead of /dev/sdb1...