I am installing Linux on a machine and got the Ubuntu 18.04 LTS image. I formatted a 32 GB Sandisk drive on macOS with MS-DOS (FAT) format and GUID Partition Map scheme.
I found the name of the disk as
disk2s2 (either with Disk Utility or
diskutil list in Terminal), unmounted and copied the image with
dd following these instructions:
diskutil unmount /dev/disk2s2 sudo dd if=~/Downloads/ubuntu-18.04.2-desktop-amd64.iso of=/dev/rdisk2s2 bs=1m
I inserted the USB on the Dell machine, booted, pressed F12 to go into "Boot Once" menu, chose legacy boot with USB, and got
Selected boot device failed. Press any key to reboot the system.
When I follow the instructions from Ubuntu and flash the ISO image on the USB with Etcher, it works and I see an extra option in "Boot Once":
UEFI SanDisk, Partition 1, which I chose and was able to try Linux.
What else do I need to create a bootable USB of Ubuntu with
dd, or all in the command line?