The home lab is my LAVA development environment and I've recently got two iMX53 Quick Start Boards working with a typical LAVA master image based on a Linaro build of Linux 3.1.0 for mx5 with a Ubuntu Oneiric Ocelot 11.10 rootfs:

3.1.0-1002-linaro-lt-mx5 (buildd@hubbard) (gcc version 4.6.1 (Ubuntu/Linaro 4.6.1-9ubuntu3) ) #13-Ubuntu PREEMPT Fri Dec 16 01:21:07 UTC 2011

As part of my Debian work, it was clearly time to look at a current, Debian, kernel and rootfs and as I'm developing and testing on Debian unstable, this would necessarily mean testing the Debian ARMMP (multi-platform) kernel which replaces the mx5 build used in Wheezy:

Linux version 3.12-1-armmp ( (gcc version 4.8.2 (Debian 4.8.2-10) ) #1 SMP Debian 3.12.9-1 (2014-02-01)

I will be scripting the creation of a suitable image for these tests and there are other changes planned in LAVA to make it easier to build suitable images, but it is useful to document just how I worked out how to build the first image.

Manual build steps

First, I've already discovered that the u-boot on the iMX53 doesn't like ext4, so the first step was to prepare an ext3 filesystem for the image. With a SATA drive attached, it was also much better to use that than the SD card, at least for generating the image. I'm also doing this natively, so I am working inside the booted master image. This is fine as the master is designed to manipulate test images, so the only package I needed to install on the LAVA master image was debootstrap I had an empty SATA drive to play with for these tests, so first prepare an ext3 filesystem:

# mkfs.ext3 /dev/sda1
# mkdir /mnt/sata
# mount /dev/sda1 /mnt/sata
# mkdir /mnt/sata/chroots/

Start the debootstrap:

# apt-get update
# apt-get install debootstrap
# debootstrap --arch=armhf --include=linux-image-armmp \
 --verbose unstable \

Various actions in this chroot will need proc, so mount it here:

# chroot /mnt/sata/chroots/unstable-armhf
# mount proc -t proc /proc
# mount devpts -t devpts /dev/pts
# exit

You may also have to edit the apt sources - the LAVA master image doesn't have editors installed, so either use echo or download an edited file. I'm using:

deb sid main

flash-kernel needs changes

For the initial tests, I've got to get this image to boot directly from u-boot, so flash-kernel is going to be needed inside the chroot and to get the iMX53 to work with the ARMMP kernel and Device Tree, flash-kernel will need an update which will mean a patch:

# chroot /mnt/sata/chroots/unstable-armhf
# apt-get update
# apt-get install patch flash-kernel
# cp /usr/share/flash-kernel/db/all.db /home
# cd /home
# patch -p2

The patch itself goes through a couple of iterations. Initially, it is enough to use:

 Machine: Freescale MX53 LOCO Board
-Kernel-Flavors: mx5
+Kernel-Flavors: armmp
+DTB-Id: imx53-qsb.dtb
+DTB-Append: yes

Later, once the device has booted with the ARMMP kernel, the Machine Id can be updated to distinguish it from the mx5 flavour (from /proc/cpuinfo) and use the model name from the Device Tree (/proc/device-tree/model):

diff --git a/db/all.db b/db/all.db
index fab3407..41f6c78 100644
--- a/db/all.db
+++ b/db/all.db
@@ -62,6 +62,18 @@ U-Boot-Initrd-Address: 0x00800000
 Required-Packages: u-boot-tools
 Bootloader-Sets-Incorrect-Root: yes

+Machine: Freescale i.MX53 Quick Start Board
+Kernel-Flavors: armmp
+DTB-Id: imx53-qsb.dtb
+DTB-Append-From: 3.12
+Boot-DTB-Path: /boot/dtb
+U-Boot-Kernel-Address: 0x70008000
+U-Boot-Initrd-Address: 0x0
+Boot-Kernel-Path: /boot/uImage
+Boot-Initrd-Path: /boot/uInitrd
+Required-Packages: u-boot-tools
+Bootloader-Sets-Incorrect-Root: no
 Machine: Freescale MX53 LOCO Board
 Kernel-Flavors: mx5
 U-Boot-Kernel-Address: 0x70008000

(I will be filing this patch in a bug report against flash-kernel soon.) With that patched, update and run flash-kernel:

# mv all.db /usr/share/flash-kernel/db/all.db
# flash-kernel
flash-kernel: installing version 3.12-1-armmp
Generating kernel u-boot image... done.
Taking backup of uImage.
Installing new uImage.
Generating initramfs u-boot image... done.
Taking backup of uInitrd.
Installing new uInitrd.
Installing new dtb.
# exit

LAVA overlays

This will be a LAVA test image and it needs an overlay - if you want a vanilla image, set up a passwd inside the chroot instead:

# cd /mnt/sata/chroots/unstable-armhf/
# wget --no-check-certificate \
# wget --no-check-certificate \
# chroot /mnt/sata/chroots/unstable-armhf/
# dpkg -i linaro-overlay-minimal_1112.2_all.deb linaro-overlay_1112.2_all.deb
# rm linaro-overlay-minimal_1112.2_all.deb linaro-overlay_1112.2_all.deb
# exit

Changes to allow the chroot to boot

Now the chroot needs setting up as a boot image:

# chroot /mnt/sata/chroots/unstable-armhf/
# echo T0:23:respawn:/sbin/getty -L ttymxc0 115200 vt102 >> ./etc/inittab
# echo auto lo eth0 > ./etc/network/interfaces.d/mx53loco
# echo iface lo inet loopback >> ./etc/network/interfaces.d/mx53loco
# echo iface eth0 inet dhcp >> ./etc/network/interfaces.d/mx53loco
# apt-get clean
# umount /dev/pts
# umount /proc
# exit

Partitioning as a LAVA test image

This would be enough as a single partition test image but, currently, LAVA expects a much more hard-wired image. Depending on the history of the device and the need for LAVA to be able to put fresh kernel builds together with a known rootfs, LAVA has used a separate /boot and / partition in the test image for nearly all boards. Standard LAVA test images for many boards (like the iMX53) also have a small unallocated space at the start of the SD card, so until I can get LAVA upstream to handle test images of arbitrary design, I'm adapting the image to suit the expectations inside LAVA. Yes, I know but it's better to get something working before spending time fixing things to make it work better. It will be fixed, in time.

So I needed to separate out the /boot contents from the rest of the rootfs - whilst keeping the chroot itself in a state which I can easily update and use to create other images:

# cd /mnt/sata/chroots/unstable-armhf/boot/
# tar -czf ../../boot.tar.gz ./*
# cd ..
# tar -czf ../root.tar.gz ./*

Now the test image file and its partitions:

# dd if=/dev/zero of=/mnt/sata/images/empty/debian.img bs=1M count=1024
# cp /mnt/sata/images/empty/debian.img /mnt/sata/images/debian-unstable-armhf-armmp.img
# losetup /dev/loop0 /mnt/sata/images/debian-unstable-armhf-armmp.img
# parted /dev/loop0 -s unit mb mktable msdos
# parted /dev/loop0 -s unit mb mkpart primary 1 10
# parted /dev/loop0 -s unit mb mkpart primary 11 110
# parted /dev/loop0 -s unit mb mkpart primary 111 1024

I did make the mistake of using kpartx at this stage but there are many areas of confusion when translating the kpartx output to offsets for mount when parted is easier:

# parted /dev/loop0 unit B -s print
Model:  (file)
Disk /dev/loop0: 1073741824B
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start       End          Size        Type     File system  Flags
 1      1048576B    10485759B    9437184B    primary
 2      10485760B   110100479B   99614720B   primary
 3      110100480B  1024458751B  914358272B  primary

Use the Start numbers and use losetup to create the loop devices for each partition:

# losetup -o 10485760 /dev/loop1 /dev/loop0
# losetup -o 110100480 /dev/loop2 /dev/loop0
# mkfs.vfat /dev/loop1
# mkfs.ext3 /dev/loop2

Now clean up the loop mountpoints:

# losetup -d /dev/loop2
# losetup -d /dev/loop1
# losetup -d /dev/loop0
# losetup -a

losetup -a should return nothing. If it doesn't, investigate the contents of /dev/mapper and use dmsetup remove until losetup -a does report empty. Otherwise the subsequent stages will fail. Now deploy the /boot contents into the empty image:

# mount -oloop,offset=10485760 /mnt/sata/images/debian-unstable-armhf-armmp.img /mnt/boot/
# pushd /mnt/boot/
# tar -xzf /mnt/sata/chroots/boot.tar.gz
# popd
# sync
# umount /mnt/boot/

and the / contents (removing the duplicate ./boot contents):

# mount -oloop,offset=110100480 /mnt/sata/images/debian-unstable-armhf-armmp.img /mnt/root/
# pushd /mnt/root
# tar -xzf /mnt/sata/chroots/root.tar.gz
# rm ./boot/*
# popd
# sync
# umount /mnt/root

Check the image

# mount -oloop,offset=10485760 debian-unstable-armhf-armmp.img /mnt/boot
# ls /mnt/boot
config-3.12-1-armmp  initrd.img-3.12-1-armmp  uImage  uInitrd  vmlinuz-3.12-1-armmp
# umount /mnt/boot
# mount -oloop,offset=110100480 debian-unstable-armhf-armmp.img /mnt/root
# ls /mnt/root
bin  boot  dev  etc  home  initrd.img  lib  lost+found  media  mnt  opt  proc  root  run  sbin  srv  sys  tmp  usr  var  vmlinuz
# ls /mnt/root/bin/auto-serial-console
# umount /mnt/root
# md5sum debian-unstable-armhf-armmp.img


Yes, I have put that file online, if you are interested. Do read the readme first though.

Getting the image off the device

# ip a
# python -m SimpleHTTPServer 80 2>/dev/null

then wget (just http://, IP address / and the filename), md5sum - finish with Ctrl-C. Depending on setup, it may be quicker to transfer the uncompressed file over a LAN than to let the device compress it. Your main machine will do the compression much faster, even with a larger download. (It also helps to not compress the image on the device, you can test the mount offsets more easily - and do check that the image can be mounted with the offsets from parted.)


# cat /proc/cpuinfo
processor      : 0
model name     : ARMv7 Processor rev 5 (v7l)
Features       : swp half thumb fastmult vfp edsp thumbee neon vfpv3 tls vfpd32
CPU implementer        : 0x41
CPU architecture: 7
CPU variant    : 0x2
CPU part       : 0xc08
CPU revision   : 5

Hardware       : Freescale i.MX53 (Device Tree Support)
Revision       : 0000
Serial         : 0000000000000000
# uname -a
Linux imx53-02 3.12-1-armmp #1 SMP Debian 3.12.9-1 (2014-02-01) armv7l GNU/Linux
# lsb_release -a
No LSB modules are available.
Distributor ID:        Debian
Description:   Debian GNU/Linux unstable (sid)
Release:       unstable
Codename:      sid