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