How to create a bootable Ubuntu install USB from Mac OS.

I’ve been doing this for over a decade, and finally decided to document it.

1. Insert the USB into your machine

2. Find the device id

$ df -h
Filesystem      Size   Used  Avail Capacity iused      ifree %iused  Mounted on
/dev/disk1s1   466Gi   10Gi  239Gi     5%  487114 4880655046    0%   /
devfs          344Ki  344Ki    0Bi   100%    1196          0  100%   /dev
/dev/disk1s2   466Gi  214Gi  239Gi    48% 1719485 4879422675    0%   /System/Volumes/Data
/dev/disk1s5   466Gi  1.0Gi  239Gi     1%       1 4881142159    0%   /private/var/vm
map auto_home    0Bi    0Bi    0Bi   100%       0          0  100%   /System/Volumes/Data/home
/dev/disk2s2    15Gi  1.8Gi   13Gi    13%       0          0  100%   /Volumes/UNTITLED

Here, our disk is named UNTITLED and it has a device id of /dev/disk2. The trailing s2 is the partition id.

3. Unmount the partition

$ diskutil umount /dev/disk2s2
Volume UNTITLED on disk2s2 unmounted

4. Download Ubuntu 20.04

$ wget
--2020-06-02 11:49:58--
Resolving (,,, ...
Connecting to (||:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 952107008 (908M) [application/x-iso9660-image]
Saving to: ‘ubuntu-20.04-live-server-amd64.iso’

ubuntu-20.04-live-server-amd64.iso            28%[=========================>                                                                    ] 258.45M  11.9MB/s    eta 58s

5. Flash the ISO to your USB disk

Our target in this case is /dev/rdisk2

$ sudo dd if=ubuntu-20.04-live-server-amd64.iso of=/dev/rdisk2 bs=32M

6. Eject the disk

$ sudo diskutil eject /dev/rdisk2
Disk /dev/rdisk2 ejected

7. Remove the disk and boot into the flashable USB

On a mac, you need to hold the alt/option key when rebooting to boot into the disk selection. For other machines, a lot of times it is just the delete key when booting to go into the BIOS, then select to choose to boot from the flash drive

Extra Notes

  • If the image file you have downloaded ends with an .xz file extension, run:
$ xzcat ~/Downloads/<image-file.xz> | sudo dd of=<drive address> bs=32M
  • If the line is in the /dev/mmcblk0p1 format, then your drive address is: /dev/mmcblk0. If it is in the /dev/sdb1 format, then the address is /dev/sdb.
  • On Linux, run the sync command to finalize the process