EBC Exercise 08 Installing Development Tools - bitbake

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thumb‎ Embedded Linux Class by Mark A. Yoder

Early in the class most of the exercises we will do will all run on the BeagleBoard. You'll be able to edit (gedit), compile (gcc) and run all on the Beagle. Later, when we start compiling the kernel [1] or the boot loader, (U-boot) you will need to cross compile on a Linux machine and copy the results to the Beagle.

The purpose of this exercise is to install all the tools needed for compiling on your host so they will be ready when you need them.

Instructions for building Ångström are given here; however there are a few changes you have to make. Here's what I did.

Tip: Run this exercise using a wired connection if you can. The Ubuntu wireless driver can be finicky, and if it stops working you'll have to restart some of this.

Install development environment

These are the bitbake instructions. Use at your own risk.

The step is to get the crosscompilers, etc. installed. Generally you do this install on your local copy of Linux. Some of these installs can take a long time (one took me 12 hours, slow download times), so you may want to install on a remote server that's always connected to the internet. If so, see the tips [[ | below]]

Get the setup scripts

First install git by running the following on your host computer.

host$ sudo apt-get install git-core

(Here is a nice git tutorial. Take a look at it if you want to understand the commands that follow. We'll explore it in more depth in a later exercise.)

Then run the following to load the meta data.

I have everything in a ~/BeagleBoard, so here is how I setup things:

host$ cd
host$ mkdir -p BeagleBoard
host$ cd BeagleBoard
host$ git clone git://github.com/Angstrom-distribution/setup-scripts.git oe
host$ cd oe

(The git took 4.5 seconds.) This creates a directory for open embedded (oe) and gets the script to download Ångström. What files do you see?

Setting up for the BeagleBoard

Now let's setup local.conf for our needs:

$ gedit conf/local.conf

Add the following to the end of the file.

MACHINE ?= "beagleboard" 

Look at this block of lines:

# Make use of SMP and fast disks

Here you can tell it how many parallel threads to run. If you have several cores on your machine, make this number big. If you have only one core, you might be better performance setting it to 1. If you have no clue which value to pick, Gentoo users suggest 1 more than the number of cores in your computer. More details are here.

  • PARALLEL_MAKE sets the number "gcc" threads (same as make -j4 at compile time
  • BB_NUMBER_THREADS sets the number of bitbake threads, (one thread can be downloading, while another compiles)

To save you a lot of time, it is useful to disable locale generation for all but the one you need. Add this to local.conf

GLIBC_GENERATE_LOCALES = "en_US.UTF-8 en_GB.UTF-8 de_DE.UTF-8 fr_FR.UTF-8 pt_BR.UTF-8 es_ES.UTF-8 kn_IN.UTF-8 ml_IN.UTF-8 ta_IN.UTF-8"

Now run:

host$ ./oebb.sh config beagleboard

I got some errors; some things are missing

host$ ls -ls /bin/sh
0 lrwxrwxrwx 1 root root 4 Mar 29 14:53 /bin/sh -> dash
host$ sudo rm /bin/sh
host$ sudo ln -s /bin/bash /bin/sh
host$ ls -ls /bin/sh
0 lrwxrwxrwx 1 root root 9 Aug 30 10:38 /bin/sh -> /bin/bash
host$ sudo apt-get install gawk

Now try again

host$ ./oebb.sh config beagleboard
host$ ./oebb.sh update

This will bring in all the tools you need. The config took about 3.5 minutes on my machine, update took about 1 minute.

Build a small program

Before the first time you run bitbake you need to do the following to set up the environmental variables:

host$ source ~/.oe/environment-angstromv2012.05

Take a look in the file and see what it is doing.

host$ less ~/.oe/environment-angstromv2012.05

To see if everything is ready, run the following

host$ bitbake nano

nano is a small editor. We really don't need nano, but if it can be compiled we know we have everything in place. I get the following error when I run the bitbake:

Pseudo is not present but is required, building this first before the main build
ERROR:  Poky's config sanity checker detected a potential misconfiguration.
    Either fix the cause of this error or at your own risk disable the checker (see sanity.conf).
    Following is the list of potential problems / advisories:

    Please install following missing utilities: diffstat,texi2html,makeinfo,cvs,svn,chrpath

ERROR: Execution of event handler 'check_sanity_eventhandler' failed

So, some programs are missing. Install them with:

host$ sudo apt-get install diffstat texi2html texinfo subversion chrpath gettext

This took just a few minutes.

Now run:

host$ bitbake nano

This will take a while. Mine first said it has 77 tasks to do. Once those were done it had 1113 tasks.

Below is a table of the times from last year. Add your bitbake time to this year's table.

Initial bitbake nano Winter 2011-2012 runtimes
Processor Settings Run Time
8 Core virtual machine PARALLEL_MAKE = "-j8"
2.5 hours
Intel Core 2 Duo T7800, 2.60 GHz PARALLEL_MAKE = "-j2"
AMD Phenom(tm) II X3 720 Processor, 2.80 GHz PARALLEL_MAKE = "-j3"
Initial bitbake nano 2011 runtimes
Processor Settings Run Time
Dell E521 with AMD Athlon 64 dual-core PARALLEL_MAKE = "-j4"
Psyco? Yes.
1.5 hours
Intel Core 2 Duo T7800, 2.60 GHz PARALLEL_MAKE = "-j1"
Psyco? No.
Intel Core 2 Duo T7800, 2.60 GHz PARALLEL_MAKE = "-j4"
Psyco? Yes.
Ubuntu 10.04 Running in VMWare Workstation 7.1.3 Under Windows 7 32-bit

Once nano is done building you can find it with:

host$ find . -name nano

Can you figure out which one is the nano that will run on your Beagle? I found it here:


Download and Compile the Kernel

The next step is to download and compile the kernel.

We want to keep the kernel source code around so we can experiment with it. Do this:

host$ gedit conf/local.conf

Find the line near the top that says INHERIT += " rm_work " and comment it out. This will save the source code.

# INHERIT += " rm_work

Exit gedit and do the following:

host$ source ~/.oe/environment-angstromv2012.05
host$ cd ~/BeagleBoard/oe
host$ bitbake virtual/kernel

Mine says it has 769 tasks to do. It took about 1 hour to do them. Once done you should get a kernel that will work.

If you accidentally run bitbake without commenting out the above line, after it runs you can comment out the INHERIT line and then run

host$ bitbake -c clean virtual/kernel
host$ bitbake -f -c compile virtual/kernel

This second run should take less time (one timing: first run took 3.5 hours; the recompiling took 25 minutes).

Finding the Correct Kernel

When you do the bitbake virtual/kernel you get the most recent kernel. How do you know which version you got? Look in the source directory.

host$ cd ~/BeagleBoard/oe; ls -F
build/  conf/  oebb.sh*  pseudodone  scripts/  sources/

Take a look in the sources directory.

host:~/BeagleBoard/oe$ ls -F sources
bitbake/        meta-ettus/     meta-nslu2/         meta-ti/
downloads/      meta-handheld/  meta-openembedded/  meta-xilinx/
layers.txt      meta-intel/     meta-openpandora/   openembedded-core/
meta-angstrom/  meta-java/      meta-opie/
meta-browser/   meta-kde/       meta-raspberrypi/
meta-efikamx/   meta-mono/      meta-smartphone/

Here you see directories that contain information about various repositories that were used in pulling together all the sources used to build the kernel, u-boot, and the cross-compilers. Look around a bit an see what you can learn.

Let's see what was built when we made the kernel.

host:~/BeagleBoard/oe$ cd build; ls -F
sstate-cache/  tmp-angstrom_v2012_05-eglibc/

We are interested in the second directory. This is where the Angstrom build is kept, it's the 2012 version. Open Embedded can support other distributions and the software is set up so you can work with more than one distribution as the time. We're only working with Angstrom though.

The -eglibc tells us what libraries were used in making the build. We'll talk about libraries later. Look further:

host:~/BeagleBoard/oe/build$ cd tmp-angstrom_v2012_05-eglibc/; ls -F
abi_version    ccache/   qa.log           stamps/    work-shared/
buildhistory/  deploy/   saved_tmpdir     sysroots/
cache/         pkgdata/  sstate-control/  work/

I'm not sure what all of these are for, but I know the cross-compilers are kept in sysroots. Go and explore. See if you can find them. We'll work with them in a later exercise. What we want is in the work directory:

host:~/BeagleBoard/oe/build/tmp-angstrom_v2012_05-eglibc$ cd work; ls -F
all-angstrom-linux/             beagleboard-angstrom-linux-gnueabi/
armv7a-angstrom-linux-gnueabi/  x86_64-linux/

These directories contain tools based on what they work on. x86_64-linux, for example, has the tools that run on your host computer. armv7a-angstrom-linux-gnueabi has things that run on all arm processors. beagleboard-angstrom-linux-gnueabi has things that are Beagle specific, and that's where we find the kernel.

host:~/BeagleBoard/oe/build/tmp-angstrom_v2012_05-eglibc/work$ cd beagleboard-angstrom-linux-gnueabi/; ls -F

It looks like we have the 3.2.18 version of the kernel. Here's how you find out what kernel version have we've been running on the Beagle. On the Beagle run:

beagle$ uname -a
Linux beaglebone 3.2.5+ #1 Mon Feb 13 19:22:44 CET 2012 armv7l GNU/Linux

It looks like we're running the 3.2.5+ kernel. But what if you don't want the most recent kernel? You need to find the bitbake recipe for the kernel you are running. Here's how I did it, back to the host:

host$ cd ~/BeagleBoard/oe
host$ find . -name "*2.6.32*" | grep recipe

The find command looks for files and directories that contain the string 2.6.32, the grep command then displays only those that contain the string recipe in the name. What you find is the the name of the recipe for building the kernel we're interested in. Now all you have to do is bitbake it. Be sure the conf/local.conf file is set as described earlier so that the sources aren't deleted.

Note: Don't do this just yet. I'm not sure which version we need.

host$ source ~/.oe/environment-angstromv2012.05
host$ bitbake linux-omap-psp-2.6.32

I think mine took a couple of hours.

Download and Compile U-boot

While were' at it, let's get the boot loader we'll be using...

host$ bitbake u-boot

Mine took about 8 minutes.

Once installed you are ready for kernel work.

thumb‎ Embedded Linux Class by Mark A. Yoder