The hidden challenges of booting from a USB flash drive

Windows and even your motherboard could be obstacles.

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John O’Brien’s PC can’t boot from a USB drive.

Every PC needs a way to boot into something other than the installed operating system. Removable boot media allows you to repair your Windows installation when Windows itself has become unbootable. It provides a clean environment for malware scanning and removal. It also allows you to try out various flavors of Linux without having to install any of them.

Not that long ago, almost every PC had an optical drive, and booting from a CD or DVD was simple. But optical drives are becoming rare, and the only alternative boot media we have uses USB—usually a flash drive. And that can cause trouble.

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Today’s PCs come with a lot of protection—which is good—but it can get in the way. Somewhere in your BIOS setup screen, you’ll almost certainly find a Secure Boot option. If you can’t boot from a flash drive, turn it off. (The method varies from PC to PC, but Chris Hoffman offers some general guidance in his article on installing Linux on a PC with Secure Boot.)

Another issue: Most of today’s motherboards use UEFI instead of the old-fashioned BIOS, and an operating system that doesn’t support UEFI may not boot. Most motherboards support a legacy boot, but some PCs lack that option. 

Finally, most of today’s PCs boot immediately from the internal hard drive or SSD, without looking for bootable external media first. You have to do something special to make them look, and what you have to do depends on your PC.

For instance, on my Lenovo X220 laptop, I press the power button, then repeatedly press and release F12 until the boot menu comes up and I can pick the appropriate option. But before I could make that work, I had to enter the BIOS Setup (F1), make sure that that  UEFI/Legacy Boot was set to Both, and that the UEFI/Legacy Boot Priority was set to Legacy First.

I have two other Windows PCs, and each has its own unique way of doing essentially the same thing. One of them, a  ASUS Transformer Book T100, lacks legacy boot capabilities. I can boot a Windows 10 recovery drive, but not most Linux distros.

So what should you do? Go to your favorite search engine and look up the name and model of your PC (such as Lenovo X220) and either "usb boot" or "flash drive boot" including the quotation marks.

You’ll likely find useful instructions. I strongly recommend that you do this search, and test the instructions, when your PC is healthy. Then save the instructions where they can be easily accessed even when your PC won’t boot.

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