---
title: How to Prepare and Boot a USB Installer on GNU GRUB bootloader
x-toc-enable: true
...

NOTE: This guide assumes that you are using the GNU GRUB bootloader as
your *main* payload. If you're using SeaBIOS or Tianocore, the steps are quite
intuitive when compared to most other BIOS and UEFI systems.

This guide explains how to prepare a bootable USB for Retroboot systems that
can be used to install several GNU+Linux distributions. For this guide, you
will only need a USB flash drive and the `dd` utility (it's installed into all
GNU+Linux distributions, by default).

For information on actually installing specific GNU+Linux distributions, refer
to [this page](index.md).

## Prepare the USB Drive in GNU+Linux
If you downloaded your ISO while on an existing GNU+Linux system, here is how
to create the bootable GNU+Linux USB drive:

Connect the USB drive. Check `lsblk`, to confirm its device name 
(e.g., **/dev/sdX**):

    $ `lsblk`

For this example, let's assume that our drive's name is `sdb`. Make sure that
it's not mounted:

    $ `sudo umount /dev/sdb`

Overwrite the drive, writing your distro ISO to it with `dd`. For example, if
we are installing *Foobarbaz* GNU+Linux, and it's located in our Downloads
folder, this is the command we would run:

    $ `sudo dd if=~/Downloads/foobarbaz.iso of=/dev/sdb bs=8M; sync`

That's it! You should now be able to boot the installer from your USB drive
(the instructions for doing so will be given later).

## Prepare the USB drive in NetBSD
[This page](https://wiki.netbsd.org/tutorials/how_to_install_netbsd_from_an_usb_memory_stick/)
on the NetBSD website shows how to create a NetBSD bootable USB drive, from
within NetBSD itself. You should the `dd` method documented there. This will
work with any GNU+Linux ISO image.

## Prepare the USB drive in FreeBSD
[This page](https://www.freebsd.org/doc/handbook/bsdinstall-pre.html) on the
FreeBSD website shows how to create a bootable USB drive for installing
FreeBSD. Use the `dd` method documented. This will work with any GNU+Linux ISO
image.

## Prepare the USB drive in LibertyBSD or OpenBSD
If you downloaded your ISO on a LibertyBSD or OpenBSD system, here is how to
create the bootable GNU+Linux USB drive:

Connect the USB drive. Run `lsblk` to determine which drive it is:

    $ `lsblk`

To confirm that you have the correct drive, use `disklabel`. For example,
if you thought the correct drive were **sd3**, run this command:

    $ `disklabel sd3`

Make sure that the device isn't mounted, with `doas`; if it is, this command
will unmount it:

    $ `doas umount /dev/sd3i`

The `lsblk` command told you what device it is. Overwrite the drive, writing
the OpenBSD installer to it with `dd`. Here's an example:

    $ `doas dd if=gnulinux.iso of=/dev/rsdXc bs=1M; sync`

That's it! You should now be able to boot the installer from your USB drive
(the instructions for doing so will be given later).

## Debian or Devuan net install
Download the Debian or Devuan net installer. You can download the Debian ISO
from [the Debian homepage](https://www.debian.org/), or the Devuan ISO from
[the Devuan homepage](https://www.devuan.org/).

Secondly, create a bootable USB drive using the commands in
[#prepare-the-usb-drive-in-gnulinux](#prepare-the-usb-drive-in-gnulinux).

Thirdly, boot the USB and enter these commands in the GRUB terminal
(for 64-bit Intel or AMD):

    grub> `set root='usb0'`
    grub> `linux /install.amd/vmlinuz`
    grub> `initrd /install.amd/initrd.gz`
    grub> `boot`

If you are on a 32-bit system (e.g. some Thinkpad X60's) then you will need to
use these commands (this is also true for 32-bit running on 64-bit machines):

    grub> `set root='usb0'`
    grub> `linux /install.386/vmlinuz`
    grub> `initrd /install.386/initrd.gz`
    grub> `boot`

## Booting ISOLINUX Images (Automatic Method)
Boot it in GRUB using the `Parse ISOLINUX config (USB)` option. A new menu
should appear in GRUB, showing the boot options for that distro; this is a GRUB
menu, converted from the usual ISOLINUX menu provided by that distro.

## Booting ISOLINUX Images (Manual Method)
These are generic instructions. They may or may not be correct for your
distribution. You must adapt them appropriately, for whatever GNU+Linux
distribution it is that you are trying to install.

If the `ISOLINUX parser` or `Search for GRUB configuration` options won't work,
then press `C` in GRUB to access the command line, then run the `ls` command:

    grub> `ls`

Get the device name from the above output (e.g., `usb0`). Here's an example:

    grub> `cat (usb0)/isolinux/isolinux.cfg`

Either the output of this command will be the ISOLINUX menuentries for that
ISO, or link to other `.cfg` files (e.g, **/isolinux/foo.cfg**). For example,
if the file found were **foo.cfg**, you would use this command:

    grub> `cat (usb0)/isolinux/foo.cfg`

And so on, until you find the correct menuentries for ISOLINUX.

For Debian-based distros (e.g., Ubuntu, Devuan), there are typically
menuentries listed in **/isolinux/txt.cfg** or **/isolinux/gtk.cfg**. For
dual-architecture ISO images (i686 and x86\_64), there may be separate files
directories for each architecture.  Just keep searching through the image,
until you find the correct ISOLINUX configuration file.

**NOTE: Debian 8.6 ISO only lists 32-bit boot options in txt.cfg.
This is important, if you want 64-bit booting on your system. Devuan versions
based on Debian 8.x may also have the same issue.**

Now, look at the ISOLINUX menuentry; it'll look like this:

    `kernel /path/to/kernel append PARAMETERS initrd=/path/to/initrd ...`

GRUB works similarly; here are some example GRUB commands:

    grub> `set root='usb0'`
    grub> `linux /path/to/kernel PARAMETERS MAYBE\_MORE\_PARAMETERS`
    grub> `initrd /path/to/initrd`
    grub> `boot`

Note: `usb0` may be incorrect. Check the output of the `ls` command (in GRUB),
to see a list of USB devices/partitions. Of course, this will vary from distro
to distro. If you did all of that correctly, then it should now be booting your
USB drive in the way that you specified.

## Troubleshooting
Most of these issues occur when using Retroboot with Coreboot's `text-mode`
with libgfxinit for video initialization. This mode is useful for text mode
payloads, like `MemTest86+`, which expect `text-mode`, but for GNU+Linux
distributions it can be problematic when they are trying to switch to a
framebuffer, because no mode switching support is present (Linux/BSD kernels
do Kernel Mode Setting, so they are able to initialize a frame buffer in bare
metal regardless of whatever coreboot is doing).

### debian-installer Graphical Corruption in Text-Mode (Debian and Devuan)
When using the ROM images that use Coreboot's `text mode`, instead of the
VESA framebuffer, while using libgfxinit, booting the Debian or Devuan net
installer results in graphical corruption, because it is trying to switch to a
framebuffer while no mode switching support is present. Use this kernel
parameter on the `linux` line, when booting it:

    `fb=false`

This forces debian-installer to start in `text-mode`, instead of trying to
switch to a framebuffer.

If selecting `text-mode` from a GRUB menu created using the ISOLINUX parser,
you can press `E` on the menu entry to add this. Or, if you are booting
manually (from GRUB terminal), then just add the parameters.

This workaround was found on the
[Debian site](https://www.debian.org/releases/stable/i386/ch05s04.html).
It should also work for Devuan, and any other `apt-get` distro that provides
the debian-installer (i.e., text-mode) net install method.

Copyright © 2014, 2015, 2016, 2020 Leah Rowe <info@minifree.org>

Copyright © 2016 Scott Bonds <scott@ggr.com>

Copyright © 2017 Elijah Smith <esmith1412@posteo.net>

Permission is granted to copy, distribute and/or modify this document under the
terms of the GNU Free Documentation License Version 1.3 or any later version
published by the Free Software Foundation with no Invariant Sections, no Front
Cover Texts, and no Back Cover Texts. A copy of this license is found in
[../fdl-1.3.md](../fdl-1.3.md)
