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
  7843191   Image.gz-ccimx8x-sbc-pro.bin
    86501   ccimx8dx-sbc-pro-wb.dtb
    85023   ccimx8dx-sbc-pro.dtb
    86865   ccimx8qxp-sbc-pro-id135.dtb
    86865   ccimx8qxp-sbc-pro-wb.dtb
    85387   ccimx8qxp-sbc-pro.dtb
     1857   boot.scr

7 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       7843191 Sep 27 11:22 Image.gz-ccimx8x-sbc-pro.bin
-rwxr-xr-x    1 root     root          1857 Sep 27 11:22 boot.scr
-rwxr-xr-x    1 root     root         86501 Sep 27 11:22 ccimx8dx-sbc-pro-wb.dtb
-rwxr-xr-x    1 root     root         85023 Sep 27 11:22 ccimx8dx-sbc-pro.dtb
-rwxr-xr-x    1 root     root         86865 Sep 27 11:22 ccimx8qxp-sbc-pro-id135.dtb
-rwxr-xr-x    1 root     root         86865 Sep 27 11:22 ccimx8qxp-sbc-pro-wb.dtb
-rwxr-xr-x    1 root     root         85387 Sep 27 11:22 ccimx8qxp-sbc-pro.dtb

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-pro.bin

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

  • 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>