Embedded excursions part 1: Testing Yocto/Poky on Arch Linux

11 Aug 2013

I'm quite new to embedded development and embedded Linux distributions, so I'll just choose Yocto to build the root filesystem, without extensive evaluation. Sometimes is just better to get started. First I'll test if I can build the default qemux86 image. If everything goes ok, I can proceed to building root fs for my Freescale Arm board, wandboard.

About host I'm using:

$ head -1 /etc/os-release
NAME="Arch Linux"

$ uname -a
Linux qniitty 3.10.5-1-wor #1 SMP PREEMPT Sun Aug 4 21:49:08 EEST 2013
x86_64 GNU/Linux

Arch linux is not really validated to work as host with Yocto/Poky but let's try it anyway. Using Yocto v9.0.1.

$ source poky-dylan-9.0.1/oe-init-build-env build
Error: The bitbake directory (/mnt/oldhome/embed/none) does not exist!
Please ensure a copy of bitbake exists at this location

Let's see if the git version works better, before fixing old bash scripts:

$ git clone git://git.yoctoproject.org/poky poky-git
$ source poky-git/oe-init-build-env build
Bitbake is not compatible with python v3
Please set up python v2 as your default python interpreter

At least a different error and yes, in current the Arch Linux the default python interpreter is of version 3.x. Let's quickly fix poky/bitbake python scripts to use python2 as the default interpreter. The "/usr/bin/env python" shebangs can be fixed by tricking env, so no need to touch those.

$ grep -IR '/usr/bin/python' poky-git/

With some find and sed magic:

$ find poky-git/ -type f -regextype posix-extended -regex \
".*\.py" -execdir sed -i -r \
's:(#!\s?/usr/bin/python\s*$):\12:' '{}' \;

$ grep -IR '/usr/bin/python' poky-git/

Env tricking is done by adding new python symlinks to the beginning of the PATH evironment variable, so that the env finds them before the actual python executables.

$ mkdir build/python-bin
$ ln -s /usr/bin/python2 build/python-bin/python
$ ln -s /usr/bin/python2-config build/python-bin/python-config
$ export PATH=$(pwd)/build/python-bin:${PATH}
$ /usr/bin/env python
Python 2.7.5 (default, May 12 2013, 12:00:47)

And finally a quick modification to the "poky-git/scripts/oe-buildenv-internal" script which is called by the "oe-init-build-env" script.

After all this, sourcing "oe-init-build-env" works as intended:

$ source poky-git/oe-init-build-env build
You had no conf/local.conf file. This configuration file has therefore been
created for you with some default values. You may wish to edit it to use a
### Shell environment set up for builds. ###

You can now run 'bitbake <target>'

Before running bitmake, one can edit "conf/local.conf" file to set target machine and other options. For this test run the default machine "qemux86" will do.

Running bitbake in the build dir:

$ bitbake core-image-minimal
WARNING: Host distribution "Arch-Linux" has not been validated with this
version of the build system; you may possibly experience unexpected failures.
It is recommended that you use a tested distribution.
Loading cache: 100% |###############################| ETA:  00:00:00
Loaded 1175 entries from dependency cache.

Build Configuration:
BB_VERSION        = "1.19.1"
BUILD_SYS         = "x86_64-linux"
TARGET_SYS        = "i586-poky-linux"
MACHINE           = "qemux86"
DISTRO            = "poky"
DISTRO_VERSION    = "1.4+snapshot-20130811"
TUNE_FEATURES     = "m32 i586"
TARGET_FPU        = ""
meta-yocto-bsp    = "master:f63e7f4323368c0d6fe7a1d44393a7e15652d4f2"

NOTE: Resolving any missing task queue dependencies
NOTE: Preparing runqueue
NOTE: Executing SetScene Tasks
NOTE: Executing RunQueue Tasks
WARNING: Failed to fetch URL
http://www.apache.org/dist/subversion/subversion-1.7.10.tar.bz2, attempting
MIRRORS if available
NOTE: validating kernel config, see log.do_kernel_configcheck for details
NOTE: Tasks Summary: Attempted 1675 tasks of which 502 didn't need to be
rerun and all succeeded.

Summary: There were 2 WARNING messages shown.

After this qemux86 kernel and root filesystem have been generated. To test these poky script runqemu can be used (this needs sudo permission for files poky-git/scripts/runqemu-if{up,down}).

$ runqemu qemux86
Continuing with the following parameters:
KERNEL: [/mnt/oldhome/embed/build/tmp/deploy/images/bzImage-qemux86.bin]
ROOTFS: [/mnt/oldhome/embed/build/tmp/deploy/images/core-image-minimal-qemux86.ext3]
FSTYPE: [ext3]
Setting up tap interface under sudo
Acquiring lockfile for tap0...
Running qemu-system-i386...
-kernel /mnt/oldhome/embed/build/tmp/deploy/images/bzImage-qemux86.bin -net
nic,vlan=0 -net tap,vlan=0,ifname=tap0,script=no,downscript=no -hda
-show-cursor -usb -usbdevice wacom-tablet -vga vmware -no-reboot -m 128
--append "vga=0 uvesafb.mode_option=640x480-32 root=/dev/hda rw mem=128M
ip= oprofile.timer=1 "
Set 'tap0' nonpersistent
Releasing lockfile of preconfigured tap device 'tap0'

Seems to work. Next testing on the wandboard.