1. Insert U disk

2. Fdisk – l find the drive letter of U disk

3.umount /dev/sdb*

four mkfs.vfat /dev/sdb -I

5. Use the DD command to write ISO to enter the U disk
// if = input file. You should fill in the absolute address instead of ～ /… , or you can CD to the current directory and directly write the name
// of = output file

dd if=/home/zhouya/Downloads/ubuntu-20.04.2.0-desktop-amd64.iso of=/dev/sda status=progress && sync