How to Create a Bootable Linux USB on macOS

Sunday. May 04, 2025 - 4 mins

🐧 How to Create a Bootable Linux USB on macOS via CLI

This guide walks you through the process of creating a bootable USB drive for installing a Linux distribution, using only Terminal on macOS.

✅ Requirements

A USB flash drive with at least 4GB capacity (8GB+ recommended)
A downloaded .iso file for your desired Linux distribution (e.g., Ubuntu, Fedora, Debian)
macOS system with administrative access
Basic comfort with Terminal commands

🛠 Step-by-Step Instructions

1. Prepare the ISO File

Download your preferred Linux .iso from the official website. For example:

~/Downloads/debian-12.10.0-amd64-netinst.iso

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2. Convert the ISO to IMG Format

Use hdiutil to convert the .iso to a .img.dmg file:

hdiutil convert -format UDRW -o ~/Desktop/debian-12.10.0-amd64-netinst.img ~/Downloads/debian-12.10.0-amd64-netinst.iso

usb

🔍 Explanation:

hdiutil: macOS utility to manipulate disk images.
convert: Converts one disk image format to another.
-format UDRW: Specifies the Universal Disk Image Format, Read/Write. This is required because .img files need to be written directly to USB and must support raw device access.
- UDRW stands for Universal Disk Image Format - Read/Write.
- Unlike .ISO files, .IMG images in UDRW format are byte-for-byte writable using dd.
-o ~/Desktop/debian-12.10.0-amd64-netinst.img: Output path and base name (macOS will append .dmg).

✅ Output file will be: debian-12.10.0-amd64-netinst.img.dmg on your Desktop.

Note: macOS adds the .dmg extension automatically — the resulting file will be linux.img.dmg.

3. Identify the USB Drive

Insert your USB drive and list all disks:

diskutil list

Look for a device that matches your USB drive’s size (e.g., 16GB, 32GB). For example:

/dev/disk4 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
     GUID_partition_scheme                        *15.5 GB    disk4
      Microsoft Basic Data                         6.2 GB     disk4s1
                       EFI ESP                     5.2 MB     disk4s2
      Microsoft Basic Data                         307.2 KB   disk4s3
          Linux Filesystem                         9.3 GB     disk4s4

⚠️ Important: Double-check this step to avoid overwriting your system disk.

usb

4. Unmount the USB Drive

Unmount the disk (replace disk4 with your actual identifier):

diskutil unmountDisk /dev/diskX # (Replace X with your USB disk for me "5")

You should see:

Unmount of all volumes on disk4 was successful

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5. Write the IMG File to USB

Now copy the .img.dmg to the USB using the dd command:

sudo dd if=~/Desktop/debian-12.10.0-amd64-netinst.img.dmg of=/dev/rdisk4 bs=1m

if=: input file
of=: output file (use /dev/rdiskX for raw access, which is faster)
bs=1m: block size for writing

🔐 Enter your password when prompted. This process may take several minutes.

Optional: You can check progress by pressing CTRL+T during the write.

Example output:

633+0 records in
633+0 records out
663748608 bytes transferred in 161.418830 secs (4111965 bytes/sec)

usb

6. Eject the USB Drive

Once dd finishes, eject the USB drive safely:

diskutil eject /dev/disk4

usb

Now your USB drive is ready to boot.

🚀 Boot from USB

Insert the USB drive into the target computer.
Reboot and hold the Option (⌥) key at startup.
Select the USB device (usually shows up as “EFI Boot”) from the boot menu.
Begin the Linux installation process.

🧪 Troubleshooting Tips

The USB doesn’t show up in boot menu: Try recreating the USB with a different ISO, or ensure it’s a hybrid image.
Permission denied errors: Make sure you’re using sudo with dd.
Overwriting wrong disk: Always verify the disk ID with diskutil list before using dd.

🔗 References

👍 You now have a bootable Linux USB drive created using macOS without any third-party apps or Boot Camp!

Thanks for reading!

—

Guneycan Sanli

Guneycan Sanli

A person who like learning, music, travelling and sports.