Yocto Flash From Net

From Variscite Wiki
VAR-SOM-MX6 - Flash Yocto images from network

Flashing a complete Yocto system from Network using TFTP & NFS

  1. Please make sure your host system is ready to use TFTP/NFS. Use our Wiki if required: Yocto Setup TFTP/NFS
  2. This is a concept Wiki. Please adapt it to your system and your requirements.
  3. Android can be flashed in the same way.

Build minimal file system

To setup a build environment follow steps 1 & 3 of the Build Boot2Qt 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 mtd-utils imx-kobs mtd-utils-ubifs"

And build the image:

$ bitbake core-image-minimal

Create a root file system and copy files:

$ mkdir ~/flash_rootfs
$ sudo tar xf tmp/deploy/images/var-som-mx6/core-image-minimal-var-som-mx6.tar.gz -C ~/flash_rootfs
$ sudo cp tmp/deploy/images/var-som-mx6/uImage /tftpboot
$ for f in tmp/deploy/images/var-som-mx6/*.dtb; do if [[ -L $f ]] && [[ $f != *var-som-mx6.dtb ]]; then sudo cp $f /tftpboot/; fi done
$ sudo rename 's/uImage-imx/imx/' /tftpboot/uImage-*.dtb

Edit /etc/exports. E.g.

$ 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

If you want 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 SOMs internal storage (NAND flash/eMMC).
Once the file system is built you can use it again and again to flash your VAR-SOM-MX6.
You can update the images to use your images and/or customize install_yocto.sh to your requirements.