Building Kubos Linux for the ISIS-OBC


This supplementary document covers specific features and components of Kubos Linux for the ISIS-OBC.

The Kubos Linux Overview doc covers the major components of Kubos Linux.

Additionally, this document covers the steps required in order to build Kubos Linux.

Reference Documents

iOBC Documentation

The ISIS-OBC Quickstart Guide should have been packaged with the iOBC and is a useful document for learning what each of the hardware components are, how to connect them, and what drivers need to be installed to support them.

Kubos Documentation

Software Components

ISIS Bootloader

The ISIS bootloader lives in the very beginning of the NOR flash. It should come pre-loaded on the board and should not need to be modified. It initializes the memory hardware and then copies U-Boot into the SDRAM and starts its execution.

If for some reason this bootloader needs to be reloaded, the relevant instructions can be found in section 8.1 of the ISIS-OBC Quickstart Guide.


Product Page

The software tool used to program the iOBC’s NOR flash storage area.


The ISIS-OBC SDK includes the SAM-BA application. You should install this version, rather than the default Atmel version, since it is packaged with several iOBC configuration files which are required to successfully connect to the board.

Kubos Linux Build Process

If for some reason you want or need to modify and rebuild the Kubos Linux components, follow the steps in this section.

Build the OS Files


The OS files cannot be built using a synced folder in a Vagrant box (or regular VM). VirtualBox does not support hard links in shared folders, which are crucial in order to complete the build.

SSH into a Kubos SDK box

In order to build Kubos Linux, two components are needed:

These components should be setup as children of the same parent directory. There are several commands and variables in the build process which use relative file paths to navigate between the components.

After the environment has been set up, all build commands will be run from the BuildRoot directory unless otherwise stated.

To set up a build environment and build Kubos Linux:

Create a new parent folder to contain the build environment

$ mkdir kubos-linux

Enter the new folder

$ cd kubos-linux

Download BuildRoot-2017.02 (more current versions of BuildRoot may work as well, but all testing has been done against 2017.02)


All Kubos documentation will refer to v2017.02.8, which is the latest version of the LTS release at the time of this writing.

$ wget && tar xvzf buildroot-2017.02.8.tar.gz && rm buildroot-2017.02.8.tar.gz

Pull the kubos-linux-build repo

$ git clone

Move into the buildroot directory

$ cd buildroot-2017.02.8

Point BuildRoot to the external kubos-linux-build folder and tell it to build the iOBC.


You will need to build with sudo if you are using the default iOBC configuration, since it points the output toolchain to “/usr/bin/iobc_toolchain”, which is a protected directory.

$ sudo make BR2_EXTERNAL=../kubos-linux-build at91sam9g20isis_defconfig

Build everything

$ sudo make

The full build process will take a while. Running on a Linux VM, it took about an hour. Running in native Linux, it took about ten minutes. Once this build process has completed once, you can run other BuildRoot commands to rebuild only certain sections and it will go much more quickly (<5 min).

BuildRoot documentation can be found **here**

The generated files will be located in buildroot-2017.02.8/output/images. They are:

  • uboot.bin - The U-Boot binary
  • zImage - The compressed Linux kernel file
  • at91sam9g20isis.dtb - The Device Tree Binary that Linux uses to configure itself for the iOBC
  • rootfs.tar - The root file system. Contains BusyBox and other libraries

Changing the Output Toolchain Directory (optional)

If you would like to build your toolchain in somewhere other than the “/usr/bin/iobc_toolchain” directory, update the BR2_HOST_DIR variable in the “configs/at91sam9g20isis_defconfig” file.

If you would like BuildRoot to just build the toolchain locally, you may remove the BR2_HOST_DIR variable entirely. The toolchain will then be built under the main “buildroot-2017.02.8” directory in a new “output/host” folder.

Create an SD Card Image


The image script will use 4GB of system RAM during execution. By default, the Kubos Vagrant box only provides 2GB. As a result, you’ll either need to increase the amount of RAM provided to your box, or run the script natively.

A script is available to create an SD card image with the latest Kubos Linux kernel and root filesystem.

Navigate to the ‘kubos-linux-build/tools’ directory.

Run the script. You might need to run as root to get permissions for certain steps.

The script has optional parameters:

  • -d {device} - Sets the SD card device name to flash the newly created image to (does not flash by default)
  • -i {name} - Specifies the output file name of the image file to be created. (default: “kubos-linux.img”)
  • -p - Specify that existing kpack-base.itb and kernel files should be copied into the appropriate partitions
  • -pp - Specify that the kpack-base.itb and kernel files should be built and then copied to their partitions
  • -ppp - Only build and copy the kpack and kernel files. Skip all other steps.
  • -s {size} - Size, in MB, of the SD card. The default is 3800 (~4GB).
  • -b {branch} - Specify the branch name of U-Boot that has been built. The default is ‘master’. This option should not need to be used outside of development.

So if I wanted to create a custom-named image with brand new kernel files, I would run:

$ ./ -i kubos-linux-v1.0.img -pp

Create an Upgrade Package

If you would like to distribute your changes as a Kubos upgrade package instead, please refer to the Upgrade Creation instructions.