Insert the USB stick.
df
returns:
/dev/sdb1
NOTE: The last line in the output lists the USB that is mounted.
sudo umount /dev/sdb1
sudo dd bs=4M if=/home/peter/Downloads/ubuntu-20.04.2-live-server-amd64.iso of=/dev/sdb1
NOTE: Another approach to writing the USB stick is:
sudo dd bs=4M if=/home/peter/Downloads/ubuntu-20.04.2-live-server-amd64.iso of=/dev/sdb1 status=progress oflag=sync
This displays a status bar