TL;DR

Find the USB drive with diskutil list, unmount it, write the ISO to its raw device with dd, and eject it.

dd writes to whatever device you name, with no confirmation and no undo. Replace N in diskN with the number diskutil list shows for your USB drive, and check it before the third command.

$ 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.

TL;DR

When balenaEtcher stays at “Starting…” with no progress bar and no error, check the USB drive’s format. On a drive formatted as APFS, Etcher’s helper receives the write request and never starts writing. Running Etcher as sudo doesn’t change that. Erase the whole drive as exFAT and flash again.

The erase deletes everything on the drive. Replace N in diskN with the number diskutil list shows for your USB drive, and check it before the last command.

$ diskutil list
$ diskutil unmountDisk force /dev/diskN
$ diskutil eraseDisk ExFAT USB GPT /dev/diskN

If Etcher still stops, write the ISO with dd instead, as described in Create a bootable Linux USB drive on macOS with dd.

I wanted to repurpose my old Mac, a 2011 iMac, by putting Linux Mint on it. I wrote the installer USB drive on my Apple Silicon MacBook Pro with balenaEtcher. Etcher stopped at “Starting…” and gave no reason, so I wrote the drive with dd, and the iMac booted from it. Later I reproduced the hang on a second drive to find the cause.

Symptoms

balenaEtcher (also searched as Balena Etcher) detects the drive and loads the ISO. After you click Flash, the window stays at:

Starting...

No progress bar appears and no error is raised. Launching the app from a terminal with elevated permissions makes no difference:

sudo /Applications/balenaEtcher.app/Contents/MacOS/balenaEtcher

Etcher’s DevTools console shows the flasher starting and then stopping short of the write. This is Etcher 2.1.6 with an APFS-formatted drive:

Starting priviledged flasher sidecar on port 3435
/Applications/balenaEtcher.app/Contents/Resources/etcher-util
... with privileges ...
elevated pending
...
elevated granted
etcher-<id>
Connection to sidecar flasher process attempt 1 / 10 failed; retrying in 1000ms...
etcher-<id>
CHILD READY
start heartbeat
params Object
CHILD LOG: Ready ...
CHILD LOG: write requested
CHILD LOG: Image: /Users/<user>/Downloads/<image>.iso
CHILD LOG: Devices: /dev/diskN
CHILD LOG: Auto blockmapping: true
CHILD LOG: Decompress first: true

The log reaches write requested, echoes the job’s settings, and no bytes follow. In the log, <user> is your account name and <image> is the ISO you selected. N is your drive’s disk number, and <id> is a random name Etcher gives each helper run.

APFS drive that stops the helper before the write

Etcher doesn’t write the disk itself. The Electron app launches a separate privileged helper, the “sidecar flasher”, and hands it the image and the device. The CHILD LOG lines after write requested are the helper echoing that request back. Etcher asks macOS for administrator rights for the helper itself, which is what the elevated pending and elevated granted lines record, so sudo adds nothing. Run as sudo, the log is identical.

The log doesn’t show why the helper stops. The drive’s format does. I reproduced the hang with a second USB drive, a different ISO and Etcher 2.1.6, and changed only the format between two runs:

Erased as exFAT, the same flash continued straight into progress:

CHILD LOG: Decompress first: true
Flashing 1 device, 0% at 1.60 MB/s (total 1.60 MB/s) eta in 235s with 0 failed devices

That matches the reports on balena’s forums. One thread (opens in a new tab) states that Etcher doesn’t work on an APFS drive and surfaces no error. Another (opens in a new tab) with this hang was resolved by erasing the drive as exFAT.

A USB drive isn’t APFS unless someone made it so. Disk Utility offers APFS only when you erase the whole device with a GUID partition map, not when you erase a volume on a drive with the older MBR layout. I don’t know what the first drive was formatted as when it hung. dd wrote the Mint image to it without an error, so the ISO and the drive weren’t at fault.

Erase the USB drive as exFAT

The erase replaces the drive’s partition map and every volume on it. Copy off anything you need from the drive first.

1. Find the USB drive

$ diskutil list

Find the header that reads external, physical and matches your drive’s size. Its number replaces N in the next step. An APFS drive also appears a second time, as a synthesized container. Use the external, physical identifier, not the container’s.

2. Erase it

$ diskutil unmountDisk force /dev/diskN
$ diskutil eraseDisk ExFAT USB GPT /dev/diskN

force matters when Spotlight is indexing the drive. Without it, the erase can fail with Couldn't unmount disk. : (-69888) and name the process mds. USB is the new volume name; any name works, because the flash overwrites it.

3. Flash again

Select the ISO and the drive in Etcher, and click Flash. Within a few seconds, the window shows Flashing... with a percentage, and the DevTools log shows Flashing 1 device lines.

Write the ISO with dd instead

If Etcher still stops after the erase, dd writes the image without Etcher’s helper. That’s how the Mint drive in this article was written. The steps, the checks that keep dd off the wrong disk, and how to confirm the write are in Create a bootable Linux USB drive on macOS with dd.