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What are the risks to update 18.04.5 kernel (5.4.0-74) to the latest 5.4.125 to match the PREEMP_RT patch?

us flag

Good day everyone!

I see that uname -r returns 5.4.0-74 in my 18.04.5

I don't see any version like this at kernel.org. Why the dash? I hear that Ubuntu makes changes to their kernel. This suggests going to get source on kernel.org and building would break things?

I want to install the PREEMPT-RT patch and change only this setting to avoid breaking things. I assume the patch has to be the same version as the kernel version?

Not sure how this kernel choice should be made.

I see at kernel.org that 5.4.125 is latest 5.4 long-term support. is this also stable?

Totally ignorant here so any advice would help.

Thanks!

user535733 avatar
cn flag
Advice: https://stackoverflow.com/questions/51669724/install-rt-linux-patch-for-ubuntu
keith bradley avatar
us flag
great link but ... will it be risky? ... apt upgrade does not offer this newer kernel.
user535733 avatar
cn flag
Apt offers only kernels that somebody has packaged and tested. Ubuntu offers a packaged low-latency kernel (see [Ubuntu Studio](https://ubuntustudio.org/)), but not a realtime kernel ([reasons](https://help.ubuntu.com/community/UbuntuStudio/RealTimeKernel)).
keith bradley avatar
us flag
I see now that the dash represents patches or bug fix's.
keith bradley avatar
us flag
Also I have seen one person say that you should get the latest PREEMPT_RT patch as long as the 1st two numbers match ... but now I see many who say the kernel version (ie: 5.4.0) must match the PREMPT_RT version... the later seems to be the consensus.
keith bradley avatar
us flag
@user535733 ... I see that my 18.04.5 has an option for the PREEMPT_RT low latency which by default is not selected ... I should be able to rebuild with this setting and get the same thing as Ubuntu Studio ??
keith bradley avatar
us flag
What I don't understand is that default 18.04.5 kernel is labeled 5.4.0-74 ... but there is no version of that number at kernel.ubuntu.com ? How do I get the exact source I want if I need to stay at my kernel version and just change one setting?
user535733 avatar
cn flag
Try https://kernel.ubuntu.com/git/ubuntu/ubuntu-bionic-signed.git/log/?h=hwe-5.4
keith bradley avatar
us flag
Thanks but I am still confused ... (uname -r) returns 5.4.0-74 ... none of the number on your link match.
keith bradley avatar
us flag
Also when I ... apt source linux-image-&(uname -r) ... when I compile and reboot uname -r returns 5.4.114 ?? ... I am not getting the same kernel source on my PC that I want to keep.
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