Burn an ISO to USB Disk

Here is the truth about writing an ISO to a USB stick: the stick becomes the image, byte for byte – it is not a folder you copy files into. Treat it like imaging a disk and you won’t end up with a stick that won’t boot.

What it is, in plain words

An ISO image is a single file that holds a whole filesystem – usually an optical-disc image, now used for OS installers. Burning (writing) it to a USB drive means copying those bytes directly onto the device (/dev/sdX or /dev/mmcblk0), not onto a partition or a mounted folder. Afterwards the stick is the installer: bootable, with the partition layout the image defines.

On Linux the reliable tools are dd, cp (to the device), ddrescue, or friendlier wrappers like usbimager, Ventoy (keeps many ISOs on one stick), and distro tools (rpi-imager, fedora-media-writer).

Why it matters

Every Linux install, live system and recovery environment starts this way. Do it wrong – write to the wrong device, copy the ISO as a file onto a FAT partition, eject before sync finishes – and you get a stick that BIOS/UEFI ignores. Do it right and you always have a rescue key in your pocket.

An everyday analogy: pressing a vinyl record

Copying songs as files onto a USB stick is like putting MP3s on a flash drive. Burning an ISO is like pressing a record: the shape of the medium itself becomes the music. You can’t then treat that record as a folder of songs without melting it down and pressing again.

flowchart LR
  I[void.iso] --> W["write to /dev/sdX (the device)"]
  W --> B[bootable USB]
  I -. "NOT to" .-> P["/mnt/stick/file.iso"]

A hands-on example

1. Identify the stick carefully.

lsblk -o NAME,SIZE,MODEL,TRAN,MOUNTPOINT
# unplug/replug and watch which device appears – say /dev/sdb

Triple-check. dd to the wrong disk will destroy it without asking.

2. Unmount any partitions.

sudo umount /dev/sdb*

3. Write the image.

sudo dd if=~/Downloads/void-live-x86_64-YYYYMMDD.iso \
        of=/dev/sdb bs=4M status=progress oflag=sync
# or, equivalently on modern coreutils:
sudo cp ~/Downloads/void-live-x86_64-YYYYMMDD.iso /dev/sdb
sudo sync

oflag=sync (and the final sync) make sure buffers hit the metal before you pull the stick out.

4. Hybrid images. Most modern Linux ISOs are isohybrid – they work on DVD and USB alike. Windows ISOs often need woeusb or Ventoy instead of raw dd.

Ventoy alternative – keep many ISOs:

# install Ventoy onto the stick once, then just copy .iso files onto it
ventoy -i /dev/sdb
cp *.iso /mnt/ventoy/

Boot, pick the ISO from a menu.

Checking the download before you write

sha256sum -c sha256sum.txt
# or compare to the hash published on the distro's site
gpg --verify void-live-….iso.sig void-live-….iso

A corrupted ISO written perfectly still won’t boot – or worse, will fail halfway through install. Verify once; it’s cheaper than a mystery.

Persistent live systems

Some live ISOs (Ubuntu, Fedora, some Void builds) support a persistent overlay so changes survive reboot. That usually means a second partition or a file created by their tool – raw dd alone doesn’t create persistence. Read the distro’s live-USB docs if you want a travelling desktop, not just an installer.

Common misconceptions

“Drag the ISO onto the stick in a file manager.” That copies the file onto a filesystem. It will not boot.
"of=/dev/sdb1 is safer." It’s wrong. Write to the device (sdb), not a partition (sdb1).
“I can pull it out when the progress bar finishes.” Wait for sync / dd to return.
"bs=4M is magic." Bigger blocks are faster; they don’t change correctness.
“All sticks boot in all machines.” UEFI vs legacy BIOS, Secure Boot, 32-bit UEFI on some Atom tablets – have a second stick and a machine you know works.

Connections

Linux, Arch Linux, Ubuntu Common Tasks.
Raspberry Pi – same idea with rpi-imager and SD cards.
Data Recovery – if you dd’d the wrong disk.
Build – installing Void for Vikix.

using cat(1):
# cat path/to/archlinux-version-x86_64.iso > /dev/sdx
using cp(1):
# cp path/to/archlinux-version-x86_64.iso /dev/sdx
using dd:
# dd bs=4M if=path/to/archlinux-version-x86_64.iso of=/dev/sdx conv=fsync oflag=direct status=progress
using tee:
# tee < path/to/archlinux-version-x86_64.iso > /dev/sdx
using pv:
# pv path/to/archlinux-version-x86_64.iso > /dev/sdx