Help me understand the boot up process

[olivercfc]

I'm obviously missing something fundamental here.

I built an image with buildroot which creates a u-boot-tpl-spl.img, a u-boot.itb file and a root partition

Code:

        image = "u-boot-tpl-spl.img"
        offset = 32768 # 512 * 0x40 from start of sd card

        image = "u-boot.itb"
        offset = 262144 # 512 * 0x200 from start of sd card

        bootable = "yes"
        image = "rootfs.ext2"

In the rootfs partition there's a file called /boot/extlinux.conf which has the following

Code:

label rock64-buildroot
  kernel /boot/Image
  devicetree /boot/rk3328-rock64.dtb
  append console=ttyS2,1500000n8 root=/dev/mmcblk0p1 ro rootwait

This boots up and all is good.  However, I'm wondering why I can't just replace /boot/Image and /boot/rk3328-rock64.dtb (and /lib/modules/*) with the one from slack (for example) and have that boot up.

When I tried, it didn't find /boot/Image and tried to boot off the network.

What am I missing here?