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Flash Yocto Images from Network

Flashing a Complete Yocto System from the Network Using TFTP and NFS

NOTES:

  1. Please make sure your host system is ready to use TFTP/NFS. Use our Developer Center if required:

Yocto Setup TFTP/NFS

  1. This is a concept guide. Please adapt it to your system and your requirements.

  2. Android and Debian can be flashed in the same way.

Build Minimal File System

To set up a build environment, follow steps 1 and 3 of the Build Yocto from source code guide. Then, append the following to the conf/local.conf file in your Yocto build directory:

IMAGE_INSTALL:append = " bash e2fsprogs-mke2fs tar dosfstools zstd"

Build the image:

bitbake core-image-minimal

Create a root file system and copy files:

mkdir ~/flash_rootfs

sudo tar xf tmp/deploy/images/imx8mn-var-som/core-image-minimal-imx8mn-var-som*.tar.zst -C ~/flash_rootfs
sudo cp -a ~/flash_rootfs/boot/*.dtb /tftpboot
sudo cp ~/flash_rootfs/boot/Image.gz /tftpboot

Edit /etc/exports. For example:

sudo gedit /etc/exports

And add the following line to it (replace <uname> with the actual username):

/home/<uname>/flash_rootfs *(rw,sync,no_root_squash,no_all_squash,no_subtree_check)

Restart the NFS server:

sudo /etc/init.d/nfs-kernel-server restart

Insert the recovery SD card into your host PC and copy the following files from it (assuming it is mounted at /media):

sudo cp -a /media/rootfs/opt/images ~/flash_rootfs/opt/
sudo cp /media/rootfs/usr/bin/*.sh ~/flash_rootfs/usr/bin/

Boot the board, stop the autoboot to get to the U-Boot command line, and set the following environment variables:

setenv serverip <your host ip address>
setenv nfsroot /home/<your username>/flash_rootfs

To set the fdt file yourself instead of using the default auto-detection:

setenv fdt_file <relevant device tree>

setenv bootcmd 'run netboot'
saveenv
boot

On the target flash your system:

install_yocto.sh

A complete system is flashed into the SOM internal storage (NAND flash/eMMC).

Once the file system is built you can use it again and again to flash your VAR-SOM-MX8M-NANO.

You can update the images to use your images and/or customize install_yocto.sh to your requirements.