Re: How to switch between installed kernel and developed kernel

[Gidi Gal <gidi.gal.linux@xxxxxxxxx>]

I am grateful for your replies, Brend, Valdis and Bjørn.

I did some backups, decided for now to try and run my kernel on my native Linux, until I prepare a VM for testing.

I tried to install my kernel. The output showed some errors (I copied the install log at the bottom of this email). I think these errors led to an "invalid signature" error later on when I rebooted my machine.

I would be grateful if you could take a look and comment about possible solutions. Regarding my CONFIG_LOCALVERSION, it is set as follows:

CONFIG_LOCALVERSION="-GIDI_DEV"

Here is the installation output (if there's a different preferable way to attach such info, please let me know) :

gidi@gidi-Precision-3510:~/git/kernels/staging$ sudo make modules_install install
[sudo] password for gidi:          
  INSTALL arch/x86/crypto/aesni-intel.ko
...

  INSTALL sound/soundcore.ko
  DEPMOD  5.12.0-rc3-GIDI_DEV+
sh ./arch/x86/boot/install.sh 5.12.0-rc3-GIDI_DEV+ arch/x86/boot/bzImage \
System.map "/boot"
run-parts: executing /etc/kernel/postinst.d/apt-auto-removal 5.12.0-rc3-GIDI_DEV+ /boot/vmlinuz-5.12.0-rc3-GIDI_DEV+
run-parts: executing /etc/kernel/postinst.d/dkms 5.12.0-rc3-GIDI_DEV+ /boot/vmlinuz-5.12.0-rc3-GIDI_DEV+
 * dkms: running auto installation service for kernel 5.12.0-rc3-GIDI_DEV+                                                                                   [ OK ]
run-parts: executing /etc/kernel/postinst.d/initramfs-tools 5.12.0-rc3-GIDI_DEV+ /boot/vmlinuz-5.12.0-rc3-GIDI_DEV+
update-initramfs: Generating /boot/initrd.img-5.12.0-rc3-GIDI_DEV+
dpkg: warning: version '5.12.0-rc3-GIDI_DEV+' has bad syntax: invalid character in revision number
dpkg: warning: version '5.12.0-rc3-GIDI_DEV+' has bad syntax: invalid character in revision number
W: Possible missing firmware /lib/firmware/amdgpu/vangogh_gpu_info.bin for module amdgpu
...

W: Possible missing firmware /lib/firmware/i915/dg1_dmc_ver2_02.bin for module i915
dpkg: warning: version '5.12.0-rc3-GIDI_DEV+' has bad syntax: invalid character in revision number
dpkg: warning: version '5.12.0-rc3-GIDI_DEV+' has bad syntax: invalid character in revision number
run-parts: executing /etc/kernel/postinst.d/pm-utils 5.12.0-rc3-GIDI_DEV+ /boot/vmlinuz-5.12.0-rc3-GIDI_DEV+
run-parts: executing /etc/kernel/postinst.d/zz-update-grub 5.12.0-rc3-GIDI_DEV+ /boot/vmlinuz-5.12.0-rc3-GIDI_DEV+
Sourcing file `/etc/default/grub'
Sourcing file `/etc/default/grub.d/50_linuxmint.cfg'
Sourcing file `/etc/default/grub.d/init-select.cfg'
Generating grub configuration file ...
dpkg: warning: version '5.12.0~rc3-GIDI_DEV+~old' has bad syntax: invalid character in revision number
dpkg: warning: version '5.12.0~rc3-GIDI_DEV+' has bad syntax: invalid character in revision number
dpkg: warning: version '5.12.0~rc3-GIDI_DEV+' has bad syntax: invalid character in revision number
dpkg: warning: version '5.12.0~rc3-GIDI_DEV+' has bad syntax: invalid character in revision number
Found linux image: /boot/vmlinuz-5.12.0-rc3-GIDI_DEV+
Found initrd image: /boot/initrd.img-5.12.0-rc3-GIDI_DEV+
dpkg: warning: version '5.12.0~rc3-GIDI_DEV+~old' has bad syntax: invalid character in revision number
dpkg: warning: version '5.12.0~rc3-GIDI_DEV+~old' has bad syntax: invalid character in revision number
Found linux image: /boot/vmlinuz-5.12.0-rc3-GIDI_DEV+.old
Found initrd image: /boot/initrd.img-5.12.0-rc3-GIDI_DEV+
Found linux image: /boot/vmlinuz-5.4.0-64-generic
Found initrd image: /boot/initrd.img-5.4.0-64-generic
Found linux image: /boot/vmlinuz-5.4.0-58-generic
Found initrd image: /boot/initrd.img-5.4.0-58-generic
Adding boot menu entry for UEFI Firmware Settings
done

Thanks,

Gidi

On Mon, Mar 22, 2021 at 2:59 PM Bjørn Mork <bjorn@xxxxxxx> wrote:

Gidi Gal <gidi.gal.linux@xxxxxxxxx> writes:

> I am new to kernel development, currently working on
> https://kernelnewbies.org/FirstKernelPatch. I reached the step "Install
> your changes" in "Modifying a driver on native Linux". I would like to
> separate my developed kernel and my installed kernel and to switch between
> the two in order to test my changes. I am not sure that my tutorial
> explains how to do that. If you have a link that proposes a workflow for
> this request (or if my tutorial does explain this workflow and I'm missing
> the exact paragraph that does that) please let me know.

The answer depends on your choice of bootloader, distro etc.

But one way to do this is to build a native kernel package for your
distro and simply install that like any other package. So instead of

 make -j2; sudo make modules_install install

you'll do somethong like (or maybe give a more explicit version than '*')

 make -j2 bindeb-pkg; sudo dpkg -i ../linux-image-*.deb

or similare with "binrpm-pkg" for the RPM based distros.

With this you'll end up with your testing kernel as an additional choice
in the bootloader menu, keeping all your previously installed kernels as
alternatives.

Note that this way of testing is quite slow since you'll rebuild
everythng and reboot a bare metal machine.  There are easier ways to
test many kernel changes, like rebuilding only one module and load it in
your running kernel. And there is of course always a very real risk of
crashing, and possibly thrashing too...  So if you can, you might want
to run test your kernels on a virtual machine, or some other test
machine, instead of your development machine.


Bjørn

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