Custom kernel drivers

[Peng Liu]

Hi Manik,

Thanks for your information.
I have followed the steps from the link you shared with us. And I have
successfully built the image and boot the hardware. But I have a few
questions about the process to build customized Linux kernel snap and
include it in the image.

Let me explain what I have done first.
1. Use pc-kernel to build the kernel snap.
In assertion, include below field:
 "kernel": "pc-kernel"

Result: The image works fine on hardware.

2. Build the kernel snap by myself. The source code is from
https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux-snap/+git/xenial
Then I could build the image with the kernel snap built by myself (by
modifying "kernel" field in assertion and also change the command line
parameter)
#/snap/bin/ubuntu-image -c beta -o snap_test.img test.model --extra-snaps
pc-kernel_4.4.0-45-4_amd64.snap

Result: The image works fine.

3. Build the kernel snap from source code.
http://kernel.ubuntu.com/git/ubuntu/ubuntu-xenial.git/, tag
Ubuntu-4.4.0-49.70.
Then I could build the image with the kernel snap built by myself.

Result: The image does not work. The kernel boot hangs at
================================================================================
[   23.415517] random: udevadm: uninitialized urandom read (16 bytes read,
5 bits of entropy available)
[   23.415735] random: udevadm: uninitialized urandom read (16 bytes read,
5 bits of entropy available)
[   23.415982] random: udevadm: uninitialized urandom read (16 bytes read,
5 bits of entropy available)
================================================================================

I am confused about two repos for the kernel (2 and 3). Looks like the
kernel repo in method 2 does not build everything from source code, but the
repo in method 3 does.
Which repo should I use as the base to customize the kernel and add
additional drivers?

Thanks!

Peng

On Tue, Nov 15, 2016 at 11:07 PM, Manik Taneja <manik at canonical.com> wrote:

>
>
> On Tue, Nov 15, 2016 at 8:17 PM, Peng Liu <pengliu.mail at gmail.com> wrote:
>
>> Hi Folks,
>>
>> I have a related question.
>> After we build the kernel snap, how can we replace the default kernel
>> snap if we use the image from ubuntu?
>> http://releases.ubuntu.com/ubuntu-core/16/
>>
>> I tried that but snap command reported an error like "cannot replace
>> signed ** snap with an unasserted one".
>> Thanks.
>>
> Please follow the process to create your own custom Ubuntu Core image here-
>
> http://docs.ubuntu.com/core/en/guides/build-device/image-building
>
> and let us know how that goes.
>
> Cheers,
> Manik
>
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