The +vmdebootstrap +program is a a very nice system to create virtual machine images. It +create a image file, add a partition table, mount it and run +debootstrap in the mounted directory to create a Debian system on a +stick. Yesterday, I decided to try to teach it how to make images for +Raspberry Pi, as part +of a plan to simplify the build system for +the FreedomBox +project. The FreedomBox project already uses vmdebootstrap for +the virtualbox images, but its current build system made multistrap +based system for Dreamplug images, and it is lacking support for +Raspberry Pi.
+ +Armed with the knowledge on how to build "foreign" (aka non-native +architecture) chroots for Raspberry Pi, I dived into the vmdebootstrap +code and adjusted it to be able to build armel images on my amd64 +Debian laptop. I ended up giving vmdebootstrap five new options, +allowing me to replicate the image creation process I use to make +Debian +Jessie based mesh node images for the Raspberry Pi. First, the +--foreign /path/to/binfm_handler option tell vmdebootstrap to +call debootstrap with --foreign and to copy the handler into the +generated chroot before running the second stage. This allow +vmdebootstrap to create armel images on an amd64 host. Next I added +two new options --bootsize size and --boottype +fstype to teach it to create a separate /boot/ partition with the +given file system type, allowing me to create an image with a vfat +partition for the /boot/ stuff. I also added a --variant +variant option to allow me to create smaller images without the +Debian base system packages installed. Finally, I added an option +--no-extlinux to tell vmdebootstrap to not install extlinux +as a boot loader. It is not needed on the Raspberry Pi and probably +most other non-x86 architectures. The changes were accepted by the +upstream author of vmdebootstrap yesterday and today, and is now +available from +the +upstream project page.
+ +To use it to build a Raspberry Pi image using Debian Jessie, first +create a small script (the customize script) to add the non-free +binary blob needed to boot the Raspberry Pi and the APT source +list:
+ ++#!/bin/sh +set -e # Exit on first error +rootdir="$1" +cd "$rootdir" +cat <<EOF > etc/apt/sources.list +deb http://http.debian.net/debian/ jessie main contrib non-free +EOF +# Install non-free binary blob needed to boot Raspberry Pi. This +# install a kernel somewhere too. +wget https://raw.github.com/Hexxeh/rpi-update/master/rpi-update \ + -O $rootdir/usr/bin/rpi-update +chmod a+x $rootdir/usr/bin/rpi-update +mkdir -p $rootdir/lib/modules +touch $rootdir/boot/start.elf +chroot $rootdir rpi-update ++ +
Next, fetch the latest vmdebootstrap script and call it like this +to build the image:
+ ++sudo ./vmdebootstrap \ + --variant minbase \ + --arch armel \ + --distribution jessie \ + --mirror http://http.debian.net/debian \ + --image test.img \ + --size 600M \ + --bootsize 64M \ + --boottype vfat \ + --log-level debug \ + --verbose \ + --no-kernel \ + --no-extlinux \ + --root-password raspberry \ + --hostname raspberrypi \ + --foreign /usr/bin/qemu-arm-static \ + --customize `pwd`/customize \ + --package netbase \ + --package git-core \ + --package binutils \ + --package ca-certificates \ + --package wget \ + --package kmod ++ +
The list of packages being installed are the ones needed by +rpi-update to make the image bootable on the Raspberry Pi, with the +exception of netbase, which is needed by debootstrap to find +/etc/hosts with the minbase variant. I really wish there was a way to +set up an Raspberry Pi using only packages in the Debian archive, but +that is not possible as far as I know, because it boots from the GPU +using a non-free binary blob.
+ +The build host need debootstrap, kpartx and qemu-user-static and +probably a few others installed. I have not checked the complete +build dependency list.
+ +The resulting image will not use the hardware floating point unit +on the Raspberry PI, because the armel architecture in Debian is not +optimized for that use. So the images created will be a bit slower +than Raspbian based images.
+ +