The linux partition contains the following elements:

  • The kernel binary.

  • Several device tree blobs for each SOM and carrier board variant.

  • A U-Boot bootscript to boot the system.

    The main purpose of the bootscript is to select the appropriate device tree blob depending on the detected SOM variant and carrier board. This element is provided by the bootloader Yocto recipe, not the kernel.

The linux partition is formatted depending on the storage media:

Media File system

microSD

FAT

eMMC

FAT

To list the contents of the linux partition on MMC media, run ls mmc x:y in the U-Boot console where x is the device index (starting at 0) and y is the partition index (starting at 1). For example:

=> ls mmc 0:1
  7345591   image.gz-ccimx8x-sbc-express.bin
    69170   image.gz-ccimx8x-sbc-express-id129.dtb
    69170   image.gz-ccimx8x-sbc-express-wb.dtb
    68318   image.gz-ccimx8x-sbc-express.dtb
     1431   boot.scr

5 file(s), 0 dir(s)

To update the files from U-Boot console, run updatefile command. See Update files within partition.

To update the files from user space, mount the linux partition. For that, you need to mount the /dev/mmcblk0p1 device as a vfat file system.

~# mkdir /mnt/linux
~# mount -t vfat /dev/mmcblk0p1 /mnt/linux
~# ls -l /mnt/linux
-rwxr-xr-x    1 root     root         69170 Sep 18 22:01 Image.gz-ccimx8x-sbc-express-id129.dtb
-rwxr-xr-x    1 root     root         69170 Sep 18 22:01 Image.gz-ccimx8x-sbc-express-wb.dtb
-rwxr-xr-x    1 root     root       7345591 Sep 18 22:01 Image.gz-ccimx8x-sbc-express.bin
-rwxr-xr-x    1 root     root         68318 Sep 18 22:01 Image.gz-ccimx8x-sbc-express.dtb
-rwxr-xr-x    1 root     root          1431 Sep 18 22:01 boot.scr

The linux partition is automatically mounted to /mnt/linux, but as a read-only filesystem. To be able to write on the partition, remount it read/write with mount -o remount,rw /dev/mmcblk0p1 /mnt/linux.

From your development machine, you can now copy the files to the target via ssh. For example:

scp Image.gz root@<cc8x-ip>:/mnt/linux/Image.gz-ccimx8x-sbc-express.bin

When building from Yocto, all the elements are packaged together in a single file:

  • dey-image-qt-xwayland-ccimx8x-sbc-express.boot.vfat or similar on the ConnectCore 8X SBC Express.

  • dey-image-qt-xwayland-ccimx8x-sbc-pro.boot.vfat or similar on the ConnectCore 8X SBC Pro.

To update the entire linux partition from U-Boot console, save the image file to your TFTP server and use the update command in U-Boot:

=> update linux tftp <filename>