Re: Yocto Zeus -docker/PREEMPT_RT


Leon Woestenberg
 

Hello Steven,

Last entry, from July 2021, in this blog says not supported;
Docker for RTOS? - General Discussions / Feature Requests - Docker Community Forums
No, that remark is completely wrong and is mixing up things.
"RTLinux" has nothing to do with the mainstream Linux kernel (except
that RTLinux can run the Linux kernel underneath)
Forget about those remarks.


Mainstream Linux is now almost fully-featured with the PREEMPT_RT work
merged, and the Linux kernel can be configured as an RTOS capable
kernel.
There is more to hard real-time than just the kernel, but that is the
kernel part.

I would see *no reason* why Docker should not run on Linux, even when
preemptive realtime is enabled.
In contrast when searching for the PREEMPT_RT / Docker combination I
see successful results.

What is probably the cause for Docker not working, is that the kernel
configuration for the PREEMPT_RT a.k.a. "-rt" kernel in Yocto does not
enable all name space support and other capabilities that Docker
depends on.

I would start comparing .config files at this point, together with the
debug/log output of Docker.
Especially first learn which CONFIG_ options Docker depends on.

Regards,

--
Leon Woestenberg
leon@...
M: +31 6 472 30 372

Sidebranch Embedded Systems
Eindhoven, The Netherlands
http://www.sidebranch.com



On Wed, Feb 16, 2022 at 1:15 PM Monsees, Steven C (US) via
lists.yoctoproject.org
<steven.monsees=baesystems.com@...> wrote:



I have 2 platforms one with a standard kernel the other using PREEMPT_RT kernel… both work as expected.



All things being equal, when I add docker container support to both platforms, the standard kernel works just fine, but on the

PREEMPT_RT kernel docker does not appear to initialize/work correctly…



I have also tested using both ARM & Intel based HW, and appear tosee the same behavior on both.



Checking online it appears there is chatter about whether docker will run correctly under a PREEMPT_RT kernel.

Example:


Under Yocto, will docker & PREEMPT_RT kernels function correctly, is this combination supported ?

>
I am currently running zeus based platforms, docker is at version 19.03.2-ce.



Is there a patch to correct for the compatibility issues being seen ?, or

Is there a yocto version I might move to which supports both correctly ?



Any input on this would be greatly appreciated.



Thanks,

Steve







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