Switch to newer kernel installed via .dpkg

Question

TL;DR. How do I switch to a newer kernel I just compiled & packed as .deb? Generally, is there a sane way of upgrading a raspbian kernel remotely using a .deb package?

I have successfully cross-compiled the 4.4.5 RPi kernel in form of .deb packages, and installed them (specifically, linux-image-... and linux-headers-... below) on RPi.

These are the files I got after compilation:

linux-4.4.5+_4.4.5+-4.debian.tar.gz
linux-image-4.4.5+_4.4.5+-4_armhf.deb
linux-libc-dev_4.4.5+-4_armhf.deb
linux-headers-4.4.5+_4.4.5+-4_armhf.deb
linux-firmware-image-4.4.5+_4.4.5+-4_armhf.deb
linux-4.4.5+_4.4.5+.orig.tar.gz

I installed the following deb packages:

sudo dpkg -i linux-image-4.4.5+_4.4.5+-4_armhf.deb
sudo dpkg -i linux-headers-4.4.5+_4.4.5+-4_armhf.deb

Below is the contents of /boot after installation:

$ ls -lat /boot
total 30972
drwxr-xr-x 21 root root    4096 Mar 12 21:31 ..
-rwxr-xr-x  1 root root 5085910 Mar 12 21:22 initrd.img-4.4.5+
-rwxr-xr-x  1 root root  129312 Mar 12 11:54 config-4.4.5+
-rwxr-xr-x  1 root root 1995382 Mar 12 11:54 System.map-4.4.5+
-rwxr-xr-x  1 root root 4074960 Mar 12 11:54 vmlinuz-4.4.5+
drwxr-xr-x  2 root root    8192 Mar  8 12:45 .fseventsd
-rwxr-xr-x  1 root root    4096 Mar  7 21:03 ._cmdline.txt
-rwxr-xr-x  1 root root     152 Mar  7 21:03 cmdline.txt
drwxr-xr-x  3 root root    8192 Mar  7 21:01 .TemporaryItems
-rwxr-xr-x  1 root root    4096 Mar  7 21:01 ._.TemporaryItems
drwxr-xr-x  2 root root    8192 Mar  7 20:37 .Trashes
-rwxr-xr-x  1 root root    4096 Mar  7 20:37 ._.Trashes
-rwxr-xr-x  1 root root     103 Feb 26 01:17 issue.txt
-rwxr-xr-x  1 root root   18974 Feb 26 01:17 LICENSE.oracle
-rwxr-xr-x  1 root root    1635 Feb 26 01:04 config.txt
drwxr-xr-x  2 root root    8192 Feb 26 01:03 overlays
-rwxr-xr-x  1 root root   10841 Feb 25 23:22 bcm2708-rpi-b.dtb
-rwxr-xr-x  1 root root   11120 Feb 25 23:22 bcm2708-rpi-b-plus.dtb
-rwxr-xr-x  1 root root   10871 Feb 25 23:22 bcm2708-rpi-cm.dtb
-rwxr-xr-x  1 root root   12108 Feb 25 23:22 bcm2709-rpi-2-b.dtb
-rwxr-xr-x  1 root root   12575 Feb 25 23:22 bcm2710-rpi-3-b.dtb
-rwxr-xr-x  1 root root    2505 Feb 25 23:22 fixup_cd.dat
-rwxr-xr-x  1 root root    6481 Feb 25 23:22 fixup.dat
-rwxr-xr-x  1 root root    9722 Feb 25 23:22 fixup_db.dat
-rwxr-xr-x  1 root root    9724 Feb 25 23:22 fixup_x.dat
-rwxr-xr-x  1 root root 4046732 Feb 25 23:22 kernel7.img
-rwxr-xr-x  1 root root 3963140 Feb 25 23:22 kernel.img
-rwxr-xr-x  1 root root  612472 Feb 25 23:22 start_cd.elf
-rwxr-xr-x  1 root root 4888200 Feb 25 23:22 start_db.elf
-rwxr-xr-x  1 root root 2739672 Feb 25 23:22 start.elf
-rwxr-xr-x  1 root root 3840328 Feb 25 23:22 start_x.elf
-rwxr-xr-x  1 root root   17920 Feb  9 13:32 bootcode.bin
-rwxr-xr-x  1 root root    1494 Nov 18 16:01 LICENCE.broadcom
-rwxr-xr-x  1 root root   18693 Aug 21  2015 COPYING.linux
drwxr-xr-x  6 root root   16384 Jan  1  1970 .

I know it's possible to switch the kernel by setting kernel=my_kernel.img, but I don't have the image file. It's possible to run imagetool-uncompressed.py to create the image file, but it implies a little more effort. Should I be doing that instead of .deb?

Answer 1

It's not so obvious from a start but you don't have a proper image that is able to boot. Even making uImage target. Weird, but true. You need the toolset for RPi kernels :

git clone https://github.com/raspberrypi/tools.git

after that I'm usually cloning to the same dir into linux folder a kernel I desire. After that do your regular make-cycle. Install everything but the kernel. After that brew a kernel(exec from linux/ folder where you've just completed build and installed everything but the kernel) :

cd ../tools/mkimage/
./imagetool-uncompressed.py ../../linux/arch/arm/boot/Image
rm /boot/kernel.img
mv kernel.img /boot/

also there can be a file /boot/kernel7.img - if there's such a file, make a copy :

cd /boot
rm kernel7.img
cp kernel.img kernel7.img

reboot and good luck!

Answer 2

The issue is that common debian kernel package isn't designed for raspberry and doesn't provide proper kernel image.
You could simply use zImage file (which is created during cross-compilation) as a kernel image, imagetool-uncompressed.py isn't needed nowadays.

Some additional information is here: building kernel image (.img) including ramdisk

Update: I forgot about very important thing:

the loader checks kernel images for DT-compatibility, which is marked by a trailer added by the mkknlimg utility

https://www.raspberrypi.org/documentation/configuration/device-tree.md

You could find this utility in scripts directory of raspberry kernel.
I think nobody wants to build kernel without device tree support, so you need to execute
./scripts/mkknlimg arch/arm/boot/zImage kernel7.img
in rasberry kernel tree and copy kernel7.img file to boot partition on SD card (you should use kernel.img filename for the first Pi generation).