Independent reference · updated 2026-08-13
Notes on bootable media, firmware and disk images
Twelve reference guides on how a computer gets from the power button to a running system — written for people who prepare their own drives, without marketing language and without assumed knowledge.
Start here
The fundamentals, in order
If you are new to this, these four explain most of what the rest of the site assumes.
What a multiboot USB drive is, and when one is worth setting up
One drive, several system images, and a menu at power-on. Here is what that arrangement actually does and where its limits sit.
UEFI and legacy BIOS: what the difference means for bootable media
Two firmware traditions, two routes from the power button to a running system. Knowing which one your machine is following explains most boot problems.
MBR and GPT: how a drive tells the computer what is on it
Before anything can be read from a drive, something has to describe how the drive is divided. Two schemes do that job, and they are not interchangeable.
ISO, WIM, IMG and VHD: what each disk image format actually holds
Four extensions that all describe 'a disk in a file', built for four different purposes.
In practice
When something has to work on unfamiliar hardware
Preparation, verification and a troubleshooting order that saves guessing.
Backing up properly before you rewrite any drive
Preparing bootable media is a destructive operation on whichever device you point it at. Ten minutes of preparation removes almost all of the risk.
A checklist for when a bootable drive will not start
Boot problems have a small number of causes and a natural order to check them in. Working down the stack beats guessing.
Why one USB drive boots quickly and another crawls
Two drives with the same capacity and the same interface can differ by minutes on the same machine. The reasons are unglamorous and mostly invisible on the packaging.
FAT32, exFAT, NTFS: choosing a file system for a portable drive
The file system decides which machines can read your drive and how large a single file may be. Two questions, one choice.
Linux on removable media
Live sessions and what they can remember
Evaluating a system before installing it, and keeping the changes you make.
Persistence on a live Linux session, explained
A live session normally forgets everything at reboot. Persistence is the arrangement that lets it remember.
How to evaluate a Linux distribution before installing it
A live session is a test drive. Here is a checklist that turns twenty minutes of clicking around into a real evaluation.
Secure Boot, explained without the jargon
Firmware that checks a signature before running a loader. A short mechanism with a long tail of practical effects.
Source, licence, release: how open-source software is actually shipped
Three artefacts sit behind every open-source tool. Knowing what each one is for tells you a great deal about what you are running.
How to read this site
Reference material, not a shop window
Boot Media Notes is a reading site. There is nothing to download here, nothing to sign up for, and no software of any kind. Each article explains one mechanism as clearly as we can manage, states the trade-offs, and stops.
Guides are written to be read in any order, though the fundamentals make the rest easier. Every article carries the date it was last reviewed, because firmware and storage behaviour change and an unreviewed article ages badly.
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