Difference between revisions of "Emdebian on APF"

Latest revision as of 09:35, 21 January 2013

Embedded systems in general and Armadeus boards in particular have reached a CPU power level that allow them to now run Dekstop equivalent Linux distributions. The only remaining problem was the non volatile storage medium. Indeed most embedded systems come with less than 256MBytes of FLASH and so are unable to install a "normal" Linux distribution like debian for example. Problem has recently been resolved by the Emdebian project which provide size optimized debian packages. Resulting rootfs is still far from compactness of Buildroot's generated one but start to be usable on the APF configurations.

Requirements

• An APF28 with its docking board,
• A PC running a Debian stable or Ubuntu distribution (it can be in a chroot),
• A microSD card or a 128MBytes rootfs NAND partition (256 if you want a GUI).

Preamble

This page describes how to install an Emdebian stable distribution on APF28. Emdebian is mainly a Debian without documentation (manpages,etc...), so it can fit on smaller storage devices but providing the same functionalities. One of the goals in this procedure is to use the Armadeus tools as less as possible. So you won't need to change anything in u-boot configuration and buildroot will only be used to fetch and patch the kernel. The latter could have been avoided but doing this way facilitates the choice of the kernel (2.6.35.3 or a 3.x one) and ensures all the patches are applied.

Emdebian is a work in progress and the cross-toolchains in unstable are often broken so we'll stay here in the stable branches (both Emdebian and Debian).

This procedure has been written for an APF28 but should be easily adapted for another board.

Preparation

• To avoid possible ownership issues in the generated files without sudoing (I'm a bit lazy, I agree, but I doubt God keeps an eye on me...):

$ sudo su

• Working as root directly is a really *bad* idea, so I updated this tutorial accordingly --JulienB 21:26, 11 January 2013 (UTC)
• Add emdebian tools repository to your sources.list. We'll need it to install the cross-toolchain for kernel compilation:

$ sudo echo 'deb http://www.emdebian.org/debian/ stable main' >> /etc/apt/sources.list

• Install needed packages:

$ sudo apt-get update
$ sudo apt-get install multistrap 
$ sudo apt-get install uboot-mkimage g++-4.4-arm-linux-gnueabi   (if you plan to use pre-built toolchain)

multistrap is the Emdebian tool that will fetch the packages and build the rootfs.

uboot-mkimage will be needed to build the final uImage.

g++-4.4-arm-linux-gnueabi dependencies will install the whole cross-toolchain. Thanks apt :)

• Create an ext2 partition on the SD card:

# mkfs.ext2 /dev/sdc1

Building the rootfs

• Let's create a directory:

$ mkdir apf
$ cd apf

Kernel

• Get an Armadeus working tree and apply configuration:

apf/# git clone git://git.code.sf.net/p/armadeus/code armadeus
apf/# cd armadeus
armadeus/# make apf28_defconfig

Customise things you want to.

• Apply Armadeus patches:

armadeus/# export KDIR=$PWD/buildroot/output/build/linux-2.6.35.3
armadeus/# make $KDIR/.stamp_downloaded $KDIR/.stamp_extracted $KDIR/.stamp_patched

Adjust KDIR depending on the kernel you chose at the preceding step.

• Copy default configuration:

armadeus/# cp buildroot/target/device/armadeus/apf28/apf28-linux-2.6.35.3.config $KDIR/.config

• Configure and compile the kernel:

armadeus/# cd $KDIR
linux-2.6.35.3/# mkdir modout
linux-2.6.35.3/# make INSTALL_MOD_PATH=$KDIR/modout ARCH=arm CROSS_COMPILE=/usr/bin/arm-linux-gnueabi- menuconfig uImage modules modules_install

menuconfig can be omitted if you're happy with the default kernel configuration.

Now we have a kernel at $KDIR/arch/arm/boot/uImage and the modules under $KDIR/modout. Let's build the rootfs.

Multistrap

Multistrap does basically quite the same things than 'debootstrap --foreign', fetching packages from an emdebian repository, building a root tree and leaving packages unconfigured.

• Get back to the base directory:

linux-2.6.35.3/# cd ../../../../
apf28/#

• Create a config file for multistrap:

apf28/$ sudo sh -c "cat > stable.config << EOF"
[General]
arch=armel
directory=rootfs
cleanup=true
noauth=false
unpack=true
debootstrap=Grip
aptsources=Grip 

[Grip]
packages=
keyring=emdebian-archive-keyring
source=http://www.emdebian.org/grip
suite=stable
EOF

'packages=' is a space separated list of additional packages.

If you have issues with the archive keyring you can either set 'noauth=true' or download this backport:

apf28/$ wget http://backports.debian.org/debian-backports/pool/main/m/multistrap/multistrap_2.1.15~bpo60+1_all.deb
apf28/$ sudo dpkg -i multistrap_2.1.15~bpo60+1_all.deb

• Build:

apf28/$ sudo multistrap -f stable.config

• Copy the kernel and the modules:

apf28/# cp $KDIR/arch/arm/boot/uImage rootfs/boot/apf28-linux.bin
apf28/# cp -r $KDIR/modout/lib rootfs/

uImage is renamed to apf28-linux.bin so that u-boot can find it.

Finalisation

We're near the end.

• Set hostname:

apf/$ sudo sh -c "echo 'apf28' >> rootfs/etc/hostname"

• Avoid some warnings:

apf/$ sudo touch rootfs/etc/fstab

• Network configuration (address,netmask,etc...) will be inherited from u-boot, but we'll need these:

apf/$ sudo echo '127.0.0.1 localhost' >> rootfs/etc/hosts
apf/$ sudo echo 'nameserver 192.168.0.1' >> rootfs/etc/resolv.conf

• Add emdebian repository on the target repository for future packages installation, when run on board :

apf28/$ sudo sh -c "echo 'deb http://www.emdebian.org/grip/ stable main' >> rootfs/etc/apt/sources.list"

• The very last step will occur onboard. Create a shell script to be executed at first boot:

apf28/$ sudo cat > rootfs/first_boot.sh << EOF
#! /bin/sh

set -e

export PATH=/usr/sbin:/usr/bin:/sbin:/bin
export DEBIAN_FRONTEND=noninteractive
export DEBCONF_NONINTERACTIVE_SEEN=true
export LC_ALL=C
export LANGUAGE=C
export LANG=C

mount proc -t proc /proc

# Workaround configuration of dash and bash failures
# See http://lists.debian.org/debian-embedded/2011/11/msg00037.html
mkdir -p /usr/share/man/man1
/var/lib/dpkg/info/dash.preinst

# Configure packages
dpkg --configure -a

# Reset root password
sed -i -e 's/root:\*:/root::/' /etc/shadow

# Enable login through debug console
echo 'T0:23:respawn:/sbin/getty -L ttyAM0 115200 vt100' >> /etc/inittab

# Self delete
rm $0
sync
echo 'Done! You can reset the board.'
while true;
do
echo '.\c'
sleep 1
done
EOF

Note: replace ttyAM0 with the correct console device of your board, eg ttyAMA0 for APF28 3.x kernels, ttymxc2 for APF51, ttySMX0 for APF27, etc...

• Make it executable:

apf28/$ sudo chmod +x rootfs/first_boot.sh

• Copy the rootfs on the SD:

apf28/$ sudo mkdir /mnt/sd
apf28/$ sudo mount /dev/sdc1 /mnt/sd
apf28/$ sudo cp -rp rootfs/* /mnt/sd
apf28/$ sudo umount /mnt/sd

• Put the SD card into its placeholder, poweron the base board and interrupt the automatic boot. We need to tell the kernel it must launch first_boot.sh:

BIOS> setenv extrabootargs init=/first_boot.sh
BIOS> run mmcboot

update-alternative will complain about missing manpages. It can be ignored.

This should end-up with something like that:

Done! You can reset the board.
......

So...reset the board. To boot on emdebian, just get u-boot prompt and type:

BIOS> run mmcboot

To have it permanent:

BIOS> setenv bootcmd run mmcboot
BIOS> saveenv

Issues, tips, misc...

• Sometimes U-Boot fails to load the kernel:

BIOS> run mmcboot
mmc0 is current device
Loading file "/boot/apf28-linux.bin" from mmc device 0:1 (xxa1)
MMC0: Data timeout with command 18 (status 0xe03c2020)!
 ** ext2fs_devread read error - block
** Unable to read "/boot/apf28-linux.bin" from mmc 0:1 **
## Booting kernel from Legacy Image at 40000000 ...
   Image Name:   Linux-2.6.35.3
   Created:      2012-07-02  14:05:13 UTC
   Image Type:   ARM Linux Kernel Image (uncompressed)
   Data Size:    2714300 Bytes = 2.6 MiB
   Load Address: 40008000
   Entry Point:  40008000
   Verifying Checksum ... Bad Data CRC
ERROR: can't get kernel image!

Powering off/on (not just reset) solves the problem. I'm unable to say what is faulty, u-boot, hardware, other...?

• you can also boot embdebian through your network NFS shared connection:

Copy the rootfs on your share NFS folder:

apf28/# mkdir -p /tftpboot/apf28-root
apf28/# cp -rp rootfs/* /tftpboot/apf28-root

For the first boot use

BIOS> setenv extrabootargs  init=/first_boot.sh
BIOS> run nfsboot

then after having succesfully deployed the embedebian distro:

BIOS> run nfsboot

Work in progress

• Add this lines in rootfs/first_boot.sh (to remount / in rw mode at first startup):

 ...
 mount -n proc -t proc /proc
+mount -n -t sysfs none /sys
+mount -n -o remount,rw /
 ...

• Use NAND instead of microSD. Needs Armadeus toolchain installed !

$ export LEB_COUNT=2047      # on APF28
$ export LEB_COUNT=135301    # on APF51
$ export ARMADEUS_DIR=/home/xxx/armadeus-git
$ sudo $ARMADEUS_DIR/buildroot/output/host/usr/sbin/mkfs.ubifs -d rootfs -e 0x1f800 -c $LEB_COUNT -m 0x800 -x lzo -o apf-emdebian-rootfs.ubifs
$ cp $ARMADEUS_DIR/buildroot/fs/ubifs/ubinize.cfg .
$ echo "image=apf-emdebian-rootfs.ubifs" >> ubinize.cfg
$ sudo $ARMADEUS_DIR/buildroot/output/host/usr/sbin/ubinize -o apf-emdebian-rootfs.ubi -m 0x800 -p 0x20000 -s 512 ubinize.cfg

$ cp apf-emdebian-rootfs.ubi /tftpboot/

BIOS> setenv board_name apf-emdebian
BIOS> run update_rootfs

• after installation and first boot, rootfs has to be remounted in rw to be usable:

root@apf51:~# mount -o remount,rw /

Links

• Emdebian homepage
• http://free-electrons.com/blog/embdebian-with-multistrap/