Booting from USB with GRUB

I found this information a few months ago and it has proven to be extremely useful in my Linux adventures since then. Shoutout to Szymon Krajewski for teaching me this!

Step 1: Locate your USB drive

Once you are in the GRUB console, use ls to see what you're working with.

In my cases, the USB I wanted was listed as (hd0,msdos1), but it will likely be different on your machine.

The drive labels can help you in determining which drive to use (to see the labels, use ls -l ), Hopefully you know what format the partition you're trying to boot into is.

Step 2: Enter the USB drive

Use this command to set GRUB's root directory to the USB: set root=(hd0,msdos1)

To ensure you're inside the right drive, we'll use the find command to see what files are present.

Type find / and hit TAB. The efi/boot/ folder path should exist and have some files.

Step 3: Boot from the USB drive!

Now, we need to instruct GRUB to jump into the bootloader that already lives on the USB and load it for use. This process is called chain-loading.

Use the following command to chain-load the bootloader for your installation medium:
chainloader /efi/boot/grubx64.efi

Finally, type boot!

If everything went according to plan, you should have booted into your USB!