Create a Bootable Linux USB Drive on macOS with dd

$ diskutil list
$ diskutil unmountDisk /dev/diskN
$ sudo dd if="$HOME/Downloads/linuxmint-22.3-cinnamon-64bit.iso" \
    of=/dev/rdiskN bs=1m status=progress
$ diskutil eject /dev/diskN

I wanted to repurpose my old Mac, a 2011 iMac, by putting Linux Mint on it. balenaEtcher stopped at “Starting…” on my Apple Silicon MacBook Pro. I wrote the installer drive with dd instead, and the iMac booted from it. dd ships with macOS, so nothing needs installing. It copies the image onto the device block for block, which is what Etcher’s helper does in code.

1. Identify the USB device

$ diskutil list

Find the external disk in the output. Its number replaces N in the commands that follow:

/dev/diskN (external, physical):

Before going further, confirm both:

• The header reads external, physical. Internal disks read internal, physical, and APFS containers read synthesized. Neither is your USB drive.
• The size matches your USB drive.

2. Unmount the disk

$ diskutil unmountDisk /dev/diskN

Unmount, not eject. An ejected disk is removed from /dev. An unmounted disk stays in /dev with no volume mounted, so dd can open it for writing.

3. Write the ISO

This command erases everything on the drive and replaces it with the image. sudo prompts for your administrator password.

$ sudo dd if="$HOME/Downloads/linuxmint-22.3-cinnamon-64bit.iso" \
    of=/dev/rdiskN bs=1m status=progress

Three details in that command:

• "$HOME/Downloads/...", not ~/Downloads/.... The default macOS shell, zsh, doesn’t expand a tilde after if=, and dd reports the file as missing. $HOME expands in every shell.
• rdiskN, not diskN. The r prefix names the raw device, which bypasses the buffer cache and writes faster on macOS.
• status=progress prints the bytes written as it goes, so a slow write shows progress instead of looking stalled.

On this drive, the sustained rate was about 7.6 MB/s, and the 3 GB image took about seven minutes. That rate is the drive’s own write speed, not a fault.

4. Confirm it finished

dd reports the total when it completes:

3091660800 bytes transferred in 404.24 secs (7648047 bytes/sec)

Compare the byte count with the ISO’s size:

$ stat -f %z "$HOME/Downloads/linuxmint-22.3-cinnamon-64bit.iso"

3091660800

The two numbers match and no I/O error was printed, so the write is complete. dd doesn’t read the drive back to verify it the way Etcher does. Booting from the drive, later in this article, is the verification.

When dd releases the device, macOS might report that the disk isn’t readable and offer to initialize it. Choose Ignore or Eject. Initialize opens Disk Utility, where erasing the drive would undo the write.

5. Eject

$ diskutil eject /dev/diskN

What Finder shows afterward

Finder shows unfamiliar partitions, or a fraction of the drive’s capacity. That’s expected: the ISO was written as a raw disk image, not as a file system that macOS can mount. On a 32 GB drive, the image uses about 3 GB, and the rest is outside any partition in this layout. Don’t change anything on the drive until you’ve booted from it.

To return the drive to ordinary use later, erase it as exFAT. This removes the Linux image:

$ diskutil eraseDisk ExFAT USB GPT /dev/diskN

Boot the USB drive

An Intel Mac, such as the 2011 iMac, can boot from this drive. An Apple Silicon Mac can’t.

On an Intel Mac, hold Option during startup and select the external entry. The entry is usually labeled “EFI Boot”, though the label depends on the firmware and on how the drive is enumerated.