Debian Build Release

From Variscite Wiki
VAR-SOM-MX7 - Debian Stretch 9.3 with imx_4.9.88_2.0.0_ga-var01 Linux release

1 Overview

This page describes how to build and install Debian distribution (Stretch) on Variscite boards with VAR-SOM-MX7.

Please note that the build script is based on debootstrap. As described in the following instructions, it's kindly suggested to create the build folder on the main Ubuntu volume on your host PC rather than an external media.
Using an external media, although automatically mounted, will cause debootstrap to complain about access rights (even when running the script with sudo).

2 Create build environment

These instructions were tested on Ubuntu 16.04/18.04 x64 host PCs. When using other distributions, there may be issues.

Note: Variscite provides Docker containers that can be used for a development environment as an alternative to using a virtual machine or a dedicated computer. To learn more, please see Variscite's Docker Build Environment guide.

2.1 Installing required packages

On Ubuntu building machine:

$ sudo apt-get install binfmt-support qemu qemu-user-static debootstrap kpartx \
lvm2 dosfstools gpart binutils bison git lib32ncurses5-dev libssl-dev python-m2crypto gawk wget \
git-core diffstat unzip texinfo gcc-multilib build-essential chrpath socat libsdl1.2-dev \
autoconf libtool libglib2.0-dev libarchive-dev python-git xterm sed cvs subversion \
kmod coreutils texi2html bc docbook-utils python-pysqlite2 help2man make gcc g++ \
desktop-file-utils libgl1-mesa-dev libglu1-mesa-dev mercurial automake groff curl \
lzop asciidoc u-boot-tools mtd-utils device-tree-compiler flex cmake

2.2 Deploy source

Download archive containing the build script and support files for building Debian Stretch for this board:

$ cd ~
$ git clone -b debian_stretch_mx7_var02 var_som_mx7_debian

Create environment (Internet connection should be available):

$ cd ~/var_som_mx7_debian
$ ./ -c deploy

This environment prepared to build.

3 Make Debian

3.1 Build all

Internet connection should be available

$ cd ~/var_som_mx7_debian
$ sudo ./ -c all |& tee build.log

3.2 Build by parts

3.2.1 Build bootloader

$ cd ~/var_som_mx7_debian
$ sudo ./ -c bootloader

3.2.2 Build kernel, dtb files and kernel modules

$ cd ~/var_som_mx7_debian
$ sudo ./ -c kernel
$ sudo ./ -c modules

3.2.3 Build rootfs

Internet connection should be available

$ cd ~/var_som_mx7_debian
$ sudo ./ -c rootfs

3.2.4 Pack rootfs

To create the root file system archive (rootfs.tar.gz) and UBI image (rootfs.ubi.img), run the following commands:

$ cd ~/var_som_mx7_debian
$ sudo ./ -c rtar
$ sudo ./ -c rubi

4 Create boot SD card

  1. Follow the above steps for make rootfs, kernel, bootloader;
  2. Insert the SD card to card reader connected to a host system;
  3. Run the following commands (Caution! All data on the card will be destroyed):
$ cd ~/var_som_mx7_debian
$ sudo ./ -c sdcard -d /dev/sdX

where '/dev/sdX' path to the block SD device in your system.

4.1 Create a boot SD card image using a loop device

It is also possible to use the "./" script to create a boot SD card image, while using a loop device instead of attaching a real SD card.

Create an empty file using the following command:

$ dd if=/dev/zero of=var-som-mx7-debian-sd.img bs=1M count=3720

The above command creates a 3700MiB file representing the SD card.

Attach the first available loop device to this file:

$ sudo losetup -Pf var-som-mx7-debian-sd.img

To find the actual loop device being used, run: $ losetup -a | grep var-som-mx7-debian-sd.img

Write the content to the loop device to generate the SD card image:

$ sudo ./ -c sdcard -d /dev/loopX

(Replace /dev/loopX with your actual loop device, e.g. /dev/loop0)

Detach the loop device from the file:

$ sudo losetup -d /dev/loopX

To compress the SD card image file use the following command:

$ gzip -9 var-som-mx7-debian-sd.img

To write the SD card image to a real SD card device use the following command:

$ zcat var-som-mx7-debian-sd.img.gz | sudo dd of=/dev/sdX bs=1M && sync

(Replace /dev/sdX with your actual SD device, e.g. /dev/sdb)

5 Boot the board with a bootable SD card

5.1 Setting the Boot Mode

Make sure the BOOT SELECT DIP switches on the carrier board are set correctly before you power on the board.

 0 - 0 : Boot from SD card
 1 - 0 : Boot from eMMC
 0 - 1 : Boot from NAND flash
 1 - 1 : Illegal
The VAR-SOM-MX7 SOM comes with either NAND or eMMC, but not both.

5.2 Automatic device tree selection in U-Boot

As shown in the Build Results table above, we have different kernel device trees, corresponding to our different H/W configurations (sometimes they are renamed without the "zImage-" prefix).

We implemented a script in U-Boot's environment, which sets the fdt_file environment variable based on the detected hardware.

5.2.1 Enable/Disable Automatic Device Tree selection

To enable the automatic device tree selection in U-Boot (already enabled by default):

$ setenv fdt_file undefined
$ saveenv

To disable the automatic device tree selection in U-Boot, set the device tree file manually:

$ setenv fdt_file YOUR_DTB_FILE
$ saveenv

6 Build Results

The resulted images are located in ~/var_som_mx7_debian/output/.

Image name
How to use
rootfs.tar.gz Root filesystem tarball used for installation on SD card and eMMC
rootfs.ubi.img Use for flash to nand
zImage Linux kernel image
SPL.nand SPL built for NAND. The SPL is pre-U-Boot SW component, required for DDR initialization
SPL.emmc SPL built for SD card and eMMC boot. The SPL is pre-U-Boot SW component, required for DDR initialization
u-boot.img.nand U-Boot built for NAND flash
u-boot.img.emmc U-Boot built for SD card or eMMC boot
Device Tree name
imx7d-var-som-emmc.dtb Boot from SD or eMMC
imx7d-var-som-nand.dtb Boot from NAND
imx7d-var-som-emmc-m4.dtb Boot from SD or eMMC with M4 support
imx7d-var-som-nand-m4.dtb Boot from NAND with M4 support

7 Linux console access

User name User password User descriptor
root root system administrator
user user local user
x_user used for X session access

8 Flash images to NAND / eMMC

In case you are using a SOM with NAND flash, run the following command as root to install Debian on it:


In case you are using a SOM with eMMC, run the following command as root to install Debian on it:


The above scripts are located in /usr/sbin in the rootfs of the SD card used to boot Debian.

9 How-to: Test and use an interface

Please see this section in the Yocto developer guide page. It is the same for Debian.

10 How-to: Modify the kernel configuration

To modify the kernel configuration (add/remove features and drivers) please follow the steps below:

1. $ cd ~/var_som_mx7_debian/src/kernel
2. $ sudo make ARCH=arm mrproper
3. $ sudo make ARCH=arm imx_v7_var_defconfig
4. $ sudo make ARCH=arm menuconfig
5. Navigate the menu and select the desired kernel functionality
6. Exit the menu and answer "Yes" when asked "Do you wish to save your new configuration?"
7. $ sudo make ARCH=arm savedefconfig
8. $ sudo cp arch/arm/configs/imx_v7_var_defconfig arch/arm/configs/imx_v7_var_defconfig.orig
9. $ sudo cp defconfig arch/arm/configs/imx_v7_var_defconfig
10. Follow the instructions above to rebuild kernel and modules, repack rootfs images and recreate SD card

11 Build a sample C "Hello, world!" program

Create a file called myhello.c with the following content:

#include <stdio.h>

int main() {
	printf("Hello, World!\n");
	return 0;

Export the C (cross-)compiler path:

$ export CC=~/var_som_mx7_debian/toolchain/gcc-linaro-6.3.1-2017.05-x86_64_arm-linux-gnueabihf/bin/arm-linux-gnueabihf-gcc


$ $CC myhello.c -o myhello

Now you should have an app called myhello, that can be run on your target board.
You can add it to your rootfs image or copy it directly to the rootfs on the board (using scp, for example).