blog/data/2013-10-27-vmdebootstrap-rpi.txt

   1 Title: Teaching vmdebootstrap to create Raspberry Pi SD card images
   2 Tags: english, debian, freedombox, mesh network
   3 Date: 2013-10-27 17:00
   4
   5 <p>The
   6 <a href="http://packages.qa.debian.org/v/vmdebootstrap.html">vmdebootstrap</a>
   7 program is a a very nice system to create virtual machine images.  It
   8 create a image file, add a partition table, mount it and run
   9 debootstrap in the mounted directory to create a Debian system on a
  10 stick.  Yesterday, I decided to try to teach it how to make images for
  11 <a href="https://wiki.debian.org/RaspberryPi">Raspberry Pi</a>, as part
  12 of a plan to simplify the build system for the FreedomBox project.
  13 The FreedomBox project already uses vmdebootstrap for the virtualbox
  14 images, but its home made multistrap based system for Dreamplug
  15 images, and it is lacking support for Raspberry Pi.</p>
  16
  17 <p>Armed with the knowledge on how to build "foreign" (aka non-native
  18 architecture) chroots for Raspberry Pi, I dived into the vmdebootstrap
  19 code and adjusted it to be able to build armel images on my amd64
  20 Debian laptop.  I ended up giving vmdebootstrap five new options,
  21 allowing me to replicate the image creation process I use to make
  22 <a href=http://people.skolelinux.org/pere/blog/A_Raspberry_Pi_based_batman_adv_Mesh_network_node.html"">Debian
  23 Jessie based mesh node images for the Raspberry Pi</a>.  First, the
  24 <tt>--foreign /path/to/binfm_handler</tt> option tell vmdebootstrap to
  25 call debootstrap with --foreign and to copy the handler into the
  26 generated chroot before running the second stage.  This allow
  27 vmdebootstrap to create armel images on an amd64 host.  Next I added
  28 two new options <tt>--bootsize size</tt> and <tt>--boottype
  29 fstype</tt> to teach it to create a separate /boot/ partition with the
  30 given file system type, allowing me to create an image with a vfat
  31 partition for the /boot/ stuff.  I also added a <tt>--variant
  32 variant</tt> option to allow me to create smaller images without the
  33 Debian base system packages installed.  Finally, I added an option
  34 <tt>--no-extlinux</tt> to tell vmdebootstrap to not install extlinux
  35 as a boot loader.  It is not needed on the Raspberry Pi and probably
  36 most other non-x86 architectures.  The changes were accepted by the
  37 upstream author of vmdebootstrap yesterday and today, and is now
  38 available from
  39 <a href="http://git.liw.fi/cgi-bin/cgit/cgit.cgi/vmdebootstrap/">the
  40 upstream project page</a>.</p>
  41
  42 <p>To use it to build a Raspberry Pi image using Debian Jessie, first
  43 create a small script (the customize script) to add the non-free
  44 binary blob needed to boot the Raspberry Pi and the APT source
  45 list:</p>
  46
  47 <p><pre>
  48 #!/bin/sh
  49 set -e # Exit on first error
  50 rootdir="$1"
  51 cd "$rootdir"
  52 cat <<EOF > etc/apt/sources.list
  53 deb http://http.debian.net/debian/ jessie main contrib non-free
  54 EOF
  55 # Install non-free binary blob needed to boot Raspberry Pi.  This
  56 # install a kernel somewhere too.
  57 wget https://raw.github.com/Hexxeh/rpi-update/master/rpi-update \
  58     -O $rootdir/usr/bin/rpi-update
  59 chmod a+x $rootdir/usr/bin/rpi-update
  60 mkdir -p $rootdir/lib/modules
  61 touch $rootdir/boot/start.elf
  62 chroot $rootdir rpi-update
  63 </pre></p>
  64
  65 <p>Next, fetch the latest vmdebootstrap script and call it like this
  66 to build the image:</p>
  67
  68 <pre>
  69 sudo ./vmdebootstrap \
  70     --variant minbase \
  71     --arch armel \
  72     --distribution jessie \
  73     --mirror http://http.debian.net/debian \
  74     --image test.img \
  75     --size 600M \
  76     --bootsize 64M \
  77     --boottype vfat \
  78     --log-level debug \
  79     --verbose \
  80     --no-kernel \
  81     --no-extlinux \
  82     --root-password raspberry \
  83     --hostname raspberrypi \
  84     --foreign /usr/bin/qemu-arm-static \
  85     --customize `pwd`/customize \
  86     --package netbase \
  87     --package git-core \
  88     --package binutils \
  89     --package ca-certificates \
  90     --package wget \
  91     --package kmod
  92 </pre></p>
  93
  94 <p>The list of packages being installed are the ones needed by
  95 rpi-update to make the image bootable on the Raspberry Pi, with the
  96 exception of netbase, which is needed by debootstrap to find
  97 /etc/hosts with the minbase variant.  I really wish there was a way to
  98 set up an Raspberry Pi using only packages in the Debian archive, but
  99 that is not possible as far as I know, because it boots from the GPU
 100 using a non-free binary blob.</p>
 101
 102 <p>The build host need debootstrap, kpartx and qemu-user-static and
 103 probably a few others installed.  I have not checked the complete
 104 build dependency list.</p>
 105
 106 <p>The resulting image will not use the hardware floating point unit
 107 on the Raspberry PI, because the armel architecture in Debian is not
 108 optimized for that use.  So the images created will be a bit slower
 109 than <a href="http://www.raspbian.org/">Raspbian</a> based images.</p>