USB Boot Disk

This guide describes a lazy man's way of creating a Gentoo USB install medium from existing Gentoo install ISOs. This currently only handles x86 and AMD64 (x86_64) platforms.

Prerequisites

 * One USB Stick of at least 128 MB in size (64 might work, too)
 * grub, and grub stagefiles on the PC making the USB Stick
 * loopback mount capability in the kernel, if an iso is used

Preparing the stick
Nothing much to prepare, really, you can leave the fs it has, provided you can write to it from your PC and grub is able to read it later. (The USB-Stick default vfat fs is fine).

Mount the stick somewhere in your Filesystem. This guide will assume /dev/sde for the stick and /mnt/usb for the mountpoint

Preparing the source

 * Go to a Gentoo Mirror and download the appropriate minimal disk for your target architecture, or insert Gentoo Minimal BootCD into your CDROM-drive.

mount your CD or iso (don't forget to use -o loop if mounting an iso file):

Or in case of an iso:

copy the data to the stick
copy all the files recursively from the CD or ISO to your USB Stick.

now mount your /boot partition (if you are running this on a gentoo PC and followed the installation guide you almost certainly have one) and copy the grub stages to the stick's boot/ directory

Now you can safely umount your CD/ISO and the stick

install grub
Now you only need to install grub on the stick, and you're done!

You can find out which number your USB should be by tabbing after you type the root (hd part, usually it's the last number if you plugged it in after your PC booted completely.

And then in grub, execute:

That was it. Compared to creating a whole image, it was easy.