Erlang-focused Buildroot for the BeagleBone

This README contains basic instructions for creating a system image for the BeagleBone using Buildroot. The image is meant for creating embedded Erlang nodes. Packages can easily be added using Buildroot's make menuconfig configuration editor.

Preparing your system

Buildroot requires several packages to be installed on the system before it can work. On Ubuntu, the following apt-get line is sufficient:

sudo apt-get install git-core bison flex g++ gettext texinfo libncurses5-dev pv

If you'd like to compile in HiPE support, qemu is currently needed. On recent distros it is sufficient to run "sudo apt-get install qemu-user" or similar. On Ubuntu 10.04, the default version of qemu is too old.

Download qemu from http://wiki.qemu.org/Download and compile from source by running the following:

./configure --target-list=arm-linux-user
make
sudo make install

Building

To build a disk image, run:

./build_disk_image.sh

This will result in a .img file being built. This takes a while.

If you are hacking the main image, you probably want more granularity in building everything. First tell Buildroot which configuration to use:

make beaglebone_erlang_defconfig

To build everything, run:

make

The build output is stored in the output/images directory. Subsequent builds are faster. It is possible to perform partial rebuilds. See the Buildroot website for details.

Creating a BeagleBone MicroSD card

After the build completes successfully, you should have a .img file. This is a binary image that should be written to the beginning of the MicroSD card. To do this, insert a MicroSD card. You will need to unmount any partitions that were auto-mounted before writing the .img file. The commands should be something similar to the following:

find /dev -name "sdX?" -exec umount "{}" ";"
sudo dd if=xxxxxxx.img of=/dev/sdX bs=1M

Replace sdX with the device for the MicroSD card. This can be found by looking at the end of dmesg after plugging in the MicroSD card. Be careful with this since a typo in the device file can make the system unbootable.

You may also run the following script which does the above for you:

./program_sdcard.sh xxxxxxx.img sdX

Logging in to the BeagleBone

The default root password is 'root'. You may log in at the console or via ssh.

Updating the Root FS on the BeagleBone

The Root FS is configured to mount read-only on the BeagleBone. This is done to prevent data corruption from unsafe shutdowns and as a reminder that all configuration and new packages have to end up in the buildroot configuration.

Since this can be annoying during debug, the rootfs can be mounted by running:

mount -o remount,rw /

Setting the timezone

This image uses a simpler mechanism for dealing with the timezone than what is used on desktop Linux. All timezone information is kept in /etc/TZ. To change the timezone, just edit it and place the POSIX timezone string for your location. See http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html for information on the TZ format. To keep things simple, here are some examples:

EST5EDT
GMT0
JST-9
MET-1MEST
MST7MDT
PST8PDT