Bootlin opens a new office in Lyon, France

After Toulouse and Orange, Lyon is the third city chosen for opening a Bootlin office. Since September 1st of this year (2017), Alexandre Belloni and Grégory Clement have been working more precisely in Oullins close to the subway and the train station. It is the first step to make the Lyon team grow, with the opportunity to welcome interns and engineers.


Their new desks are already crowded by many boards running our favorite system.

A Kickstarter for a low cost Marvell ARM64 board

At the beginning of October a Kickstarter campaign was launched to fund the development of a low-cost board based on one of the latest Marvell ARM 64-bit SoC: the Armada 3700. While being under $50, the board would allow using most of the Armada 3700 features:

  • Gigabit Ethernet
  • SATA
  • USB 3.0
  • miniPCIe

ESPRESSObin interfaces

The Kickstarter campaign was started by Globalscale Technologies, who has already produced numerous Marvell boards in the past: the Armada 370 based Mirabox, the Kirkwood based SheevaPlug, DreamPlug and more.

We pushed the initial support of this SoC to the mainline Linux kernel 6 months ago, and it landed in Linux 4.6. There are still a number of hardware features that are not yet supported in the mainline kernel, but we are actively working on it. As an example, support for the PCIe controller was merged in Linux 4.8, released last Sunday. According to the Kickstarter page the first boards would be delivered in January 2017 and by this time we hope to have managed to push more support for this SoC to the mainline Linux kernel.

We have been working on the mainline support of the Marvell SoC for 4 years and we are glad to see at last the first board under $50 using this SoC. We hope it will help expanding the open source community around this SoC family and will bring more contributions to the Marvell EBU SoCs.

Report on extensive real-time Linux benchmarks on AT91

The real time page I wrote for Atmel was finally released on the Linux4Sam Atmel Wiki. The purpose of this page was to help new comers to use real time features with Atmel CPUs and to present the state of the real time support.

Here are some figures associated to this work:

  • On this page I present the results of more than 300 hours of benchmarks!
  • During the setup and the tuning tests ran for more than 600 hours.
  • Analysis and formatting took a few dozen hours of work.
  • The benchmarks have been run on 3 boards, 3 flavors of Linux (vanilla, PREEMPT-RT patches, Xenomai co-kernel approach), and 2 kinds of tests (timer-based and GPIO-based)
  • Experiment with Yocto

    I recently had the opportunity to use Yocto. I already practiced quite a lot with OpenEmbedded before. You can see Yocto as a project derived from OpenEmbedded even it is a bit more than that.

    In fact, Yocto is made of Poky (a build system based on OpenEmbedded), a few added build tools (swabber, pseudo, etc.), as well as a set of meta data allowing to create embedded distributions for a number of targets.

    The strength but also the weakness of OpenEmbedded is that it a very flexible build system. It can make production root filesystems, but also a complete distribution with its ready to use package repository, and this for multiple hardware platforms. It makes it a difficult system to get started and get efficient with. Even two years ago, the OpenEmbedded documentation contributed to making it difficult to get started. Indeed, OpenEmbedded did supply some documentation, but which only started to make sense once you start mastering it. This is quite a paradox for a piece of documentation. It lacked the elements allowing developers to understand its operation well.

    With Yocto, I was pleased to realize that substantial progress had been made on this side. The project comes with documentation that is much more exhaustive and above all much more accessible for beginners. Getting started with it is still not completely straightforward, but this time, this is rather because of the complexity and the rich features of the tool.

    In a few hours, I managed to develop a minimalistic BSP (Board Support Package) for a given board (in this case a AT91SAM9G20-EK). The concept of layer allows to have a configuration layer specific to a given piece of hardware. You can even support multiple hardware platforms at once and add specific packages. A layer is indeed just a set of packages and configurations (or configuration overrides). The BSP is just a layer specific to one or several pieces of hardware.

    As you can see, even to support a simple embedded board, there is already a number of concepts to deal with. There are also multiple ways of achieving the same result but which will be easier or more difficult to maintain. The concept of “BSP” for Yocto is therefore a kind of guideline to allow the Yocto community to have a common point of reference. I will try to illustrate the use of a BSP on the AT91SAMG20-EK board here and/or on my Google+ page.

    Another significant progress is optimizing build time for a “minimalistic” target, which went down from more than three hours to just over one hour now. It remains a long time for a very simple target.

    To build a filesystem image with only a few components, Buildroot remains much more appropriate. For systems that require a great number of components, more advanced functionality is then often needed, such as managing a package repository and supporting multiple hardware platforms at once for example. In this case, Yocto remains the best (the only?) option, all the more as this project addresses the traditional weaknesses of OpenEmbedded.

    A new tool to ease kernel maintainer life

    When you are involved in mainlining or maintaining some kernel code, a non negligible part of your time is spent checking patches or patchsets themselves . It is not the most interesting part but it is truly necessary to help merging in kernel code, or to make sure you don’t break anything, for example building with an incompatible configuration.

    Aiaiai developed by Artem Bityutskiy is a tool to do most of this task for you! It uses other checking tools and scripts such as sparse, coccinelle and checkpatch.pl, and comes with its own set of tools and scripts. I don’t know what does “aiaiai” stands for, but in French it sounds like “Ouch Ouch Ouch”, the sound you could make if you forget to use this tool 😉

    PS: On my G+ post, Yegor Yefremov pointed that “aiaiai” means something like “tsk tsk!” (shame on you!) in Russian.

    Building a small Debian root filesystem with Multistrap

    There are several ways to build a root filesystem for an embedded Linux system: Buildroot and Open Embedded are the usual solutions to do this. They allow to fine tune the contents of your filesystem. The drawback is, in both cases, that you need to build everything from sources and this can take from tens of minutes to several hours.

    Sometimes you don’t need all this flexibility and you just want to have a ready-to-use root filesystem, to which you just add a few extra programs. In this case using a distribution is a good solution. So let’s see what we need:

    • A binary distribution
    • Available on several architectures
    • Ability to generate a “small” root filesystem
    • A large choice of packages

    Oh, I think it is a pretty good description of Debian!

    Emdebian is a project to adapt Debian to embedded devices. A good description from the Debian wiki is:

    “In short, what EmDebian does is wrap around the regular Debian package building tools to provide a more fine grained control over package selection, size, dependencies and content to enable creation of very small and efficient Debian packages for use on naturally resource limited embedded targets.”

    And so, pretty recently (2009), Emdebian released Multistrap which is similar to Debootstrap but more appropriate for embedded devices. It seems better by the way it builds a system:

    It works in a completely different way by simply using apt and dpkg, rather than avoiding to use them, which is how Debootstrap works.

    And also more appropriate by its goals:

    It is focused on producing rootfs images for devices, as opposed to chroots for existing machines

    Practical case: build a root filesystem for the USB A9263 board from Calao Systems (arm926ejs based board).

    A drawback of Multistrap is its limitation to Debian, but in fact it is also usable on any distribution based on Debian. In our case, we ran it on an Ubuntu 10.04 system.

    First, let’s install Multistrap:

    $sudo apt-get install multistrap dpkg-dev

    Multistrap needs a config file. For our needs we just use the example one given by Embedian. Let’s name it multistrap.conf:

    [General]
    noauth=true
    unpack=true
    debootstrap=Grip
    aptsources=Grip
    
    [Grip]
    # space separated package list
    source=http://www.emdebian.org/grip
    suite=lenny
    

    Grip is the name of the lightweight Debian distro built by Emdebian.

    Now we can run Multistrap:

    $ multistrap -a armel -d $PWD/RFS -f multistrap.conf
    em_multistrap 0.0.8 using multistrap.conf
    Using foreign architecture: armel
    em_multistrap building armel multistrap on 'amd64'
    INF: Setting ./lib64 -> ./lib symbolic link.
    Getting package lists: apt-get  -o Apt::Architecture=armel -o Apt::Get::AllowUnauthenticated=true -o Apt::Get::Download-Only=true -o Apt::Install-Recommends=false -o Dir=/home/mike/celf/multistrap/RFS/ -o Dir::Etc=/home/mike/celf/multistrap/RFS/etc/apt/ -o Dir::Etc::SourceList=/home/mike/celf/multistrap/RFS/etc/apt/sources.list.d/multistrap.sources.list -o Dir::State=/home/mike/celf/multistrap/RFS/var/lib/apt/ -o Dir::State::Status=/home/mike/celf/multistrap/RFS/var/lib/dpkg/status -o Dir::Cache=/home/mike/celf/multistrap/RFS/var/cache/apt/ update
    Get:1 http://www.emdebian.org lenny Release.gpg [197B]
    Ign http://www.emdebian.org/grip/ lenny/main Translation-en_US
    Get:2 http://www.emdebian.org lenny Release [21.4kB]
    Ign http://www.emdebian.org lenny Release
    Ign http://www.emdebian.org lenny/main Packages
    Ign http://www.emdebian.org lenny/main Sources
    Ign http://www.emdebian.org lenny/main Packages
    Ign http://www.emdebian.org lenny/main Sources
    Get:3 http://www.emdebian.org lenny/main Packages [293kB]
    Get:4 http://www.emdebian.org lenny/main Sources [351kB]
    Fetched 665kB in 0s (6,280kB/s)                     
    Reading package lists... Done
    W: GPG error: http://www.emdebian.org lenny Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY B5B7720097BB3B58
    W: Duplicate sources.list entry http://www.emdebian.org/grip/ lenny/main Packages (/home/mike/celf/multistrap/RFS/var/lib/apt/lists/www.emdebian.org_grip_dists_lenny_main_binary-armel_Packages)
    Use of uninitialized value within %packages in join or string at /usr/sbin/em_multistrap line 294.
    Use of uninitialized value within %keyrings in join or string at /usr/sbin/em_multistrap line 296.
    apt-get -y  -o Apt::Architecture=armel -o Apt::Get::AllowUnauthenticated=true -o Apt::Get::Download-Only=true -o Apt::Install-Recommends=false -o Dir=/home/mike/celf/multistrap/RFS/ -o Dir::Etc=/home/mike/celf/multistrap/RFS/etc/apt/ -o Dir::Etc::SourceList=/home/mike/celf/multistrap/RFS/etc/apt/sources.list.d/multistrap.sources.list -o Dir::State=/home/mike/celf/multistrap/RFS/var/lib/apt/ -o Dir::State::Status=/home/mike/celf/multistrap/RFS/var/lib/dpkg/status -o Dir::Cache=/home/mike/celf/multistrap/RFS/var/cache/apt/ install balloon3-config base-files base-passwd bash bsdutils coreutils debianutils diff dpkg e2fslibs e2fsprogs findutils gcc-4.3-base grep grip-config gzip hostname initscripts libacl1 libattr1 libblkid1 libc6 libcap1 libcomerr2 libdevmapper1.02.1 libgcc1 liblocale-gettext-perl libncurses5 libpam-modules libpam-runtime libpam0g libselinux1 libsepol1 libslang2 libss2 libstdc++6 libtext-charwidth-perl libtext-iconv-perl libtext-wrapi18n-perl libuuid1 libvolume-id0 login lsb-base makedev mawk mktemp mount ncurses-base ncurses-bin passwd perl-base procps sed sysv-rc sysvinit sysvinit-utils tar tzdata util-linux zlib1g
    Reading package lists... Done
    Building dependency tree... Done
    The following extra packages will be installed:
      apt debconf debconf-i18n debian-archive-keyring dhcp3-client dhcp3-common gnupg gpgv ifupdown libbz2-1.0 libdb4.6 libncursesw5 libnewt0.52 libpopt0
      libreadline5 libssl0.9.8 libusb-0.1-4 lzma module-init-tools nano net-tools netbase ntpdate readline-common udev wget whiptail
    The following NEW packages will be installed:
      apt balloon3-config base-files base-passwd bash bsdutils coreutils debconf debconf-i18n debian-archive-keyring debianutils dhcp3-client dhcp3-common diff
      dpkg e2fslibs e2fsprogs findutils gcc-4.3-base gnupg gpgv grep grip-config gzip hostname ifupdown initscripts libacl1 libattr1 libblkid1 libbz2-1.0 libc6
      libcap1 libcomerr2 libdb4.6 libdevmapper1.02.1 libgcc1 liblocale-gettext-perl libncurses5 libncursesw5 libnewt0.52 libpam-modules libpam-runtime libpam0g
      libpopt0 libreadline5 libselinux1 libsepol1 libslang2 libss2 libssl0.9.8 libstdc++6 libtext-charwidth-perl libtext-iconv-perl libtext-wrapi18n-perl
      libusb-0.1-4 libuuid1 libvolume-id0 login lsb-base lzma makedev mawk mktemp module-init-tools mount nano ncurses-base ncurses-bin net-tools netbase
      ntpdate passwd perl-base procps readline-common sed sysv-rc sysvinit sysvinit-utils tar tzdata udev util-linux wget whiptail zlib1g
    0 upgraded, 87 newly installed, 0 to remove and 0 not upgraded.
    Need to get 15.4MB of archives.
    After this operation, 48.4MB of additional disk space will be used.
    WARNING: The following packages cannot be authenticated!
      libstdc++6 libbz2-1.0 readline-common libncurses5 libreadline5 libusb-0.1-4 zlib1g gpgv gnupg debian-archive-keyring apt debianutils dhcp3-common
      libattr1 libacl1 libselinux1 coreutils lzma dpkg perl-base liblocale-gettext-perl libtext-iconv-perl libtext-charwidth-perl libtext-wrapi18n-perl
      debconf-i18n debconf dhcp3-client sed ncurses-bin lsb-base module-init-tools libssl0.9.8 wget hostname net-tools ifupdown mawk libncursesw5 nano netbase
      libcap1 ntpdate libpam-runtime libpam0g libdb4.6 libpam-modules passwd libvolume-id0 udev libslang2 libnewt0.52 libpopt0 whiptail grip-config
      gcc-4.3-base libgcc1 libc6 base-passwd base-files bash diff libcomerr2 e2fslibs libuuid1 libblkid1 libss2 e2fsprogs findutils grep gzip login mktemp
      mount libsepol1 sysvinit-utils initscripts sysv-rc sysvinit tar tzdata util-linux balloon3-config bsdutils libdevmapper1.02.1 makedev ncurses-base procps
    Authentication warning overridden.
    Get:1 http://www.emdebian.org/grip/ lenny/main libstdc++6 4.3.2-1.1em1 [268kB]
    Get:2 http://www.emdebian.org/grip/ lenny/main libbz2-1.0 1.0.5-1em1 [37.2kB]
    Get:3 http://www.emdebian.org/grip/ lenny/main readline-common 5.2-3.1em1 [3,202B]
    Get:4 http://www.emdebian.org/grip/ lenny/main libncurses5 5.7+20081213-1em1 [165kB]
    Get:5 http://www.emdebian.org/grip/ lenny/main libreadline5 5.2-3.1em1 [108kB]
    Get:6 http://www.emdebian.org/grip/ lenny/main libusb-0.1-4 2:0.1.12-13em1 [13.7kB]
    Get:7 http://www.emdebian.org/grip/ lenny/main zlib1g 1:1.2.3.3.dfsg-12em1 [48.1kB]
    Get:8 http://www.emdebian.org/grip/ lenny/main gpgv 1.4.9-3+lenny1em1 [139kB]
    Get:9 http://www.emdebian.org/grip/ lenny/main gnupg 1.4.9-3+lenny1em1 [533kB]
    Get:10 http://www.emdebian.org/grip/ lenny/main debian-archive-keyring 2010.08.28~lenny1em1 [17.9kB]
    Get:11 http://www.emdebian.org/grip/ lenny/main apt 0.7.20.2+lenny2em1 [514kB]
    Get:12 http://www.emdebian.org/grip/ lenny/main debianutils 2.30em1 [23.4kB]
    Get:13 http://www.emdebian.org/grip/ lenny/main dhcp3-common 3.1.1-6+lenny4em1 [157kB]
    Get:14 http://www.emdebian.org/grip/ lenny/main libattr1 1:2.4.43-2em1 [7,706B]
    Get:15 http://www.emdebian.org/grip/ lenny/main libacl1 2.2.47-2em1 [14.0kB]
    Get:16 http://www.emdebian.org/grip/ lenny/main libselinux1 2.0.65-5em1 [50.0kB]
    Get:17 http://www.emdebian.org/grip/ lenny/main coreutils 6.10-6em1 [1,162kB]
    Get:18 http://www.emdebian.org/grip/ lenny/main lzma 4.43-14em1 [51.0kB]
    Get:19 http://www.emdebian.org/grip/ lenny/main dpkg 1.14.29em1 [405kB]
    Get:20 http://www.emdebian.org/grip/ lenny/main perl-base 5.10.0-19lenny2em1 [905kB]
    Get:21 http://www.emdebian.org/grip/ lenny/main liblocale-gettext-perl 1.05-4em1 [11.0kB]
    Get:22 http://www.emdebian.org/grip/ lenny/main libtext-iconv-perl 1.7-1+b1em1 [11.2kB]
    Get:23 http://www.emdebian.org/grip/ lenny/main libtext-charwidth-perl 0.04-5+b1em1 [6,656B]
    Get:24 http://www.emdebian.org/grip/ lenny/main libtext-wrapi18n-perl 0.06-6em1 [4,444B]
    Get:25 http://www.emdebian.org/grip/ lenny/main debconf-i18n 1.5.24em1 [2,882B]
    Get:26 http://www.emdebian.org/grip/ lenny/main debconf 1.5.24em1 [110kB]
    Get:27 http://www.emdebian.org/grip/ lenny/main dhcp3-client 3.1.1-6+lenny4em1 [185kB]
    Get:28 http://www.emdebian.org/grip/ lenny/main sed 4.1.5-6em1 [23.8kB]
    Get:29 http://www.emdebian.org/grip/ lenny/main ncurses-bin 5.7+20081213-1em1 [70.8kB]
    Get:30 http://www.emdebian.org/grip/ lenny/main lsb-base 3.2-20em1 [5,888B]
    Get:31 http://www.emdebian.org/grip/ lenny/main module-init-tools 3.4-1em1 [44.5kB]
    Get:32 http://www.emdebian.org/grip/ lenny/main libssl0.9.8 0.9.8g-15+lenny8em1 [713kB]
    Get:33 http://www.emdebian.org/grip/ lenny/main wget 1.11.4-2+lenny2em1 [116kB]
    Get:34 http://www.emdebian.org/grip/ lenny/main hostname 2.95em1 [5,808B]
    Get:35 http://www.emdebian.org/grip/ lenny/main net-tools 1.60-22em1 [156kB]
    Get:36 http://www.emdebian.org/grip/ lenny/main ifupdown 0.6.8+nmu1em1 [18.9kB]
    Get:37 http://www.emdebian.org/grip/ lenny/main mawk 1.3.3-11.1em1 [51.2kB]
    Get:38 http://www.emdebian.org/grip/ lenny/main libncursesw5 5.7+20081213-1em1 [187kB]
    Get:39 http://www.emdebian.org/grip/ lenny/main nano 2.0.7-5em1 [83.6kB]
    Get:40 http://www.emdebian.org/grip/ lenny/main netbase 4.34em1 [11.6kB]
    Get:41 http://www.emdebian.org/grip/ lenny/main libcap1 1:1.10-14em1 [7,574B]
    Get:42 http://www.emdebian.org/grip/ lenny/main ntpdate 1:4.2.4p4+dfsg-8lenny3em1 [36.1kB]
    Get:43 http://www.emdebian.org/grip/ lenny/main libpam-runtime 1.0.1-5+lenny1em1 [7,786B]
    Get:44 http://www.emdebian.org/grip/ lenny/main libpam0g 1.0.1-5+lenny1em1 [41.0kB]
    Get:45 http://www.emdebian.org/grip/ lenny/main libdb4.6 4.6.21-11em1 [531kB]
    Get:46 http://www.emdebian.org/grip/ lenny/main libpam-modules 1.0.1-5+lenny1em1 [160kB]
    Get:47 http://www.emdebian.org/grip/ lenny/main passwd 1:4.1.1-6+lenny1em1 [267kB]
    Get:48 http://www.emdebian.org/grip/ lenny/main libvolume-id0 0.125-7+lenny3em1 [18.2kB]
    Get:49 http://www.emdebian.org/grip/ lenny/main udev 0.125-7+lenny3em1 [145kB]
    Get:50 http://www.emdebian.org/grip/ lenny/main libslang2 2.1.3-3em1 [266kB]
    Get:51 http://www.emdebian.org/grip/ lenny/main libnewt0.52 0.52.2-11.3+lenny1em1 [36.7kB]
    Get:52 http://www.emdebian.org/grip/ lenny/main libpopt0 1.14-4em1 [22.3kB]
    Get:53 http://www.emdebian.org/grip/ lenny/main whiptail 0.52.2-11.3+lenny1em1 [11.7kB]
    Get:54 http://www.emdebian.org/grip/ lenny/main grip-config 0.1.2em1 [11.5kB]
    Get:55 http://www.emdebian.org/grip/ lenny/main gcc-4.3-base 4.3.2-1.1em1 [5,496B]
    Get:56 http://www.emdebian.org/grip/ lenny/main libgcc1 1:4.3.2-1.1em1 [23.7kB]
    Get:57 http://www.emdebian.org/grip/ lenny/main libc6 2.7-18lenny4em1 [4,410kB]
    Get:58 http://www.emdebian.org/grip/ lenny/main base-passwd 3.5.20em1 [11.5kB]
    Get:59 http://www.emdebian.org/grip/ lenny/main base-files 5lenny7em1 [49.2kB]
    Get:60 http://www.emdebian.org/grip/ lenny/main bash 3.2-4em1 [364kB]
    Get:61 http://www.emdebian.org/grip/ lenny/main diff 2.8.1-12em1 [59.6kB]
    Get:62 http://www.emdebian.org/grip/ lenny/main libcomerr2 1.41.3-1em1 [6,366B]
    Get:63 http://www.emdebian.org/grip/ lenny/main e2fslibs 1.41.3-1em1 [91.3kB]
    Get:64 http://www.emdebian.org/grip/ lenny/main libuuid1 1.41.3-1em1 [10.8kB]
    Get:65 http://www.emdebian.org/grip/ lenny/main libblkid1 1.41.3-1em1 [21.6kB]
    Get:66 http://www.emdebian.org/grip/ lenny/main libss2 1.41.3-1em1 [10.9kB]
    Get:67 http://www.emdebian.org/grip/ lenny/main e2fsprogs 1.41.3-1em1 [234kB]
    Get:68 http://www.emdebian.org/grip/ lenny/main findutils 4.4.0-2em1 [160kB]
    Get:69 http://www.emdebian.org/grip/ lenny/main grep 2.5.3~dfsg-6em1 [128kB]
    Get:70 http://www.emdebian.org/grip/ lenny/main gzip 1.3.12-6+lenny1em1 [44.0kB]
    Get:71 http://www.emdebian.org/grip/ lenny/main login 1:4.1.1-6+lenny1em1 [50.6kB]
    Get:72 http://www.emdebian.org/grip/ lenny/main mktemp 1.5-9em1 [5,772B]
    Get:73 http://www.emdebian.org/grip/ lenny/main mount 2.13.1.1-1em1 [69.3kB]
    Get:74 http://www.emdebian.org/grip/ lenny/main libsepol1 2.0.30-2em1 [96.4kB]
    Get:75 http://www.emdebian.org/grip/ lenny/main sysvinit-utils 2.86.ds1-61em1 [17.8kB]
    Get:76 http://www.emdebian.org/grip/ lenny/main initscripts 2.86.ds1-61em1 [33.6kB]
    Get:77 http://www.emdebian.org/grip/ lenny/main sysv-rc 2.86.ds1-61em1 [13.7kB]
    Get:78 http://www.emdebian.org/grip/ lenny/main sysvinit 2.86.ds1-61em1 [46.8kB]
    Get:79 http://www.emdebian.org/grip/ lenny/main tar 1.20-1+lenny1em1 [148kB]
    Get:80 http://www.emdebian.org/grip/ lenny/main tzdata 2010j-0lenny1em1 [749kB]
    Get:81 http://www.emdebian.org/grip/ lenny/main util-linux 2.13.1.1-1em1 [293kB]
    Get:82 http://www.emdebian.org/grip/ lenny/main balloon3-config 0.6 [2,400B]
    Get:83 http://www.emdebian.org/grip/ lenny/main bsdutils 1:2.13.1.1-1em1 [17.0kB]
    Get:84 http://www.emdebian.org/grip/ lenny/main libdevmapper1.02.1 2:1.02.27-4em1 [44.1kB]
    Get:85 http://www.emdebian.org/grip/ lenny/main makedev 2.3.1-88em1 [15.8kB]
    Get:86 http://www.emdebian.org/grip/ lenny/main ncurses-base 5.7+20081213-1em1 [16.4kB]
    Get:87 http://www.emdebian.org/grip/ lenny/main procps 1:3.2.7-11em1 [160kB]
    Fetched 15.4MB in 3s (4,819kB/s)
    Download complete and in download only mode
    I: Calculating obsolete packages
    I: Extracting apt_0.7.20.2+lenny2em1_armel.deb...
     -> Processing conffiles for apt
    I: Extracting balloon3-config_0.6_all.deb...
    I: Extracting base-files_5lenny7em1_armel.deb...
     -> Processing conffiles for base-files
    I: Extracting base-passwd_3.5.20em1_armel.deb...
    I: Extracting bash_3.2-4em1_armel.deb...
     -> Processing conffiles for bash
    I: Extracting bsdutils_1%3a2.13.1.1-1em1_armel.deb...
    I: Extracting coreutils_6.10-6em1_armel.deb...
    I: Extracting debconf-i18n_1.5.24em1_all.deb...
    I: Extracting debconf_1.5.24em1_all.deb...
     -> Processing conffiles for debconf
    I: Extracting debian-archive-keyring_2010.08.28~lenny1em1_all.deb...
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    I: Unpacking complete.
    Get:1 http://www.emdebian.org lenny Release.gpg [197B]
    Ign http://www.emdebian.org/grip/ lenny/main Translation-en_US
    Get:2 http://www.emdebian.org lenny Release [21.4kB]
    Ign http://www.emdebian.org lenny Release
    Ign http://www.emdebian.org lenny/main Packages
    Ign http://www.emdebian.org lenny/main Sources
    Ign http://www.emdebian.org lenny/main Packages
    Ign http://www.emdebian.org lenny/main Sources
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    Hit http://www.emdebian.org lenny/main Sources
    Fetched 198B in 0s (2,020B/s)
    Reading package lists... Done
    W: GPG error: http://www.emdebian.org lenny Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY B5B7720097BB3B58
    
    Multistrap system installed successfully in /home/mike/celf/multistrap/RFS/.

    Let’s explain the parameters:

    • armel is the architecture, for our example: arm in little endian
    • -d $PWD/RFS is the output directory containing the root filesystem. Be careful to pass an absolute path.
    • -f multistrap.conf is the name of the configuration file

    If you look at RFS/dev, you will see that there are no device files in it. This will be a problem at boot time, unless you build a kernel with the below options:

    CONFIG_DEVTMPFS=y
    CONFIG_DEVTMPFS_MOUNT=y
    

    Thanks to these parameters, the kernel will automatically mount a tmpfs filesystem on /dev, and will populate it with devices present on the system.

    Now we have a root filesystem, but we still need to run the package configuration scripts to make it usable. The packages were installed, but their configuration scripts couldn’t be executed, because they can only run on the target architecture.

    The easiest way to do this is to use NFS. On the host side, you need to export the root filesystem directory through NFS. On the target side you have to select /bin/sh for the init process. A typical kernel command could be:

    console=ttyS0,115200 root=/dev/nfs nfsroot=192.168.0.1:/path/RFS rw ip=192.168.0.20 init=/bin/sh

    Then boot your board. You should reach a command line.

    First mount /proc:

    mount -t proc nodev /proc
    

    Then configure your packages using this command line:

    PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin  dpkg --configure -a 

    You will get a few questions about localization for tzdata, then the packages will be configured.

    Finally go back to your host to change the RFS/etc/inittab file by uncommenting the below line and modifying it according to your serial console configuration (usually 115200). For example, replace

    #T0:23:respawn:/sbin/getty -L ttyS0 9600 vt100

    by

    T0:23:respawn:/sbin/getty -L ttyS0 115200 vt100

    As we built this root filesystem as a normal user we may have problems with some setuid programs, which need to be owned by the root user. So let’s change the ownership of some directories:

    sudo chown root:root -R RFS/bin RFS/usr/bin RFS/sbin RFS/usr/sbin

    The last trick is to delete the root password by modifying RFS/etc/passwd, by replacing

    root:x:0:0:root:/root:/bin/bash

    by

    root::0:0:root:/root:/bin/bash

    You can now reboot your system without the init=/bin/sh kernel parameter. We now have a ready to use embedded Linux root filesystem with the power of Debian.

    Other things to fix and do:

    • Configure the /etc/resolv.conf file to be able to connect to the Internet.
    • Configure the gateway in the ip= kernel parameter (ip=client-ip:server-ip:gw-ip:netmask:hostname:device:autoconf). For example:
      bootargs=console=ttyS0,115200n8 root=/dev/nfs ip=192.168.2.100::192.168.2.1:255.255.255.0:emdebian:eth0:off nfsroot=192.168.2.1:/home/mike/work/celf/
    • Install other packages such as mtd-utils and vim
    • Install kernel modules (either manually or through a kernel package)
    • Add a new user
    • Create a minimum /etc/fstab file

    You now have a Debian system for which it is very easy to add new software, and which can be configured in a very familiar way. That’s great to make product prototypes, small, low-power and secure servers for home or office use, and in some cases, even real products.