[CentOS] always boot from Elrepo kernel

johan.vermeulen7 at telenet.be johan.vermeulen7 at telenet.be
Mon Sep 26 13:48:43 UTC 2016



----- Oorspronkelijk bericht -----
Van: "Johnny Hughes" <johnny at centos.org>
Aan: centos at centos.org
Verzonden: Maandag 26 september 2016 15:14:23
Onderwerp: Re: [CentOS] always boot from Elrepo kernel

On 09/26/2016 04:29 AM, johan.vermeulen7 at telenet.be wrote:
> 
> 
> ----- Oorspronkelijk bericht -----
> Van: "Jim Perrin" <jperrin at centos.org>
> Aan: centos at centos.org
> Verzonden: Donderdag 22 september 2016 17:19:42
> Onderwerp: Re: [CentOS] always boot from Elrepo kernel
> 
> 
> 
> On 09/22/2016 10:14 AM, johan.vermeulen7 at telenet.be wrote:
>> Hello All, 
>>
>> I purchased some Dell Latitude 3570 laptops. They came with Ubuntu preinstalled. ( Which I swapped for Centos7) 
>> I have to use Elrepo kernel on these machines to get some of the fn function keys to work. 
>> So I installed Elrepo's kernel-ml and selected this kernel with: 
>> # grub2-set-default 0 
>> ( after disabling secure boot) 
>>
>> The problem I see is that after a next kernel update, the new Centos kernel will be nr 0 and the machine will 
>> boot from that kernel if I tested this correctly. 
>>
>> Is there a way I can enable elrepo kernel update but not the regular Centos kernel? 
> 
> I believe you need to update /etc/sysconfig/kernel to set the 'default'
> kernel package to be the kernel-ml or whichever elrepo kernel you're using.
> 
> Hello Jim,
> 
> thanks for the reply.
> For some reason that doesnt' work.
> To test this I booted from an older kernel and removed the most recent Centos-kernel
> After installing Elrepo's kernel-ml the system boots from kernel-ml, with or without changing /etc/sysconfig/kernel to
> DEFAULTKERNEL=kernel-ml
> But after running an update again, and reinstalling the latest Centos kernel, the system boots from that kernel again.

There is no reason to keep the CentOS Kernel on your machines if the
elrepo kernel is what you want to use.

You should be able to (1) boot from an elrepo kernel then do:

rpm -qa | grep kernel | sort

then pick out the CentOS kernels and do:

rpm -e <kernel> <kernel1>

where <kernel> and <kernel1> are the name-version of the kernel you want
to remove.

Then you should not get updates for the CentOS Kernels, only for elrepo
ones.

The advice Jim gave you will then allow an update of 'kernel-ml' to
actually update the grub.

One thing to think about is that you need to update some other packages
besides kernel to use the latest kernels on CentOS.  These include
xfsprogs, where without the new fsck.xfs, you can not properly fix
errors in an xfs file system.  See this bugL

https://bugzilla.redhat.com/show_bug.cgi?id=1314605

You can get a fairly updated kernel and xfsprogs (and a new supermin and
some other packages here):

http://mirror.centos.org/altarch/7/experimental/x86_64/Packages/

You can exclude the kernel and just grab the xfsprogs if you want as well.

My plan is to update that repo to the latest 4.4.x periodically while
the 4.4 tree is in LTS.  I will move that branch to another kernel once
LTS 4.4 support stops.

NOTE:  I am not suggesting that kernel is better than any of the elrepo
kernels, nor am I trying to compete with those kernels.  I created this
kernel for arm32 and i686 (and possibly aarch64) for the altarch SIGs so
that we can support newer IoT products .. I also intend to build the
x86_64 because we can and to give IoT users the ability to have the same
kernel across several arches.  I love elrepo and use it on several
machines .. either choice is absolutely fine :)

Thanks,
Johnny Hughes

Hello Johnny,

thanks for the reply.
I 'll try that kernel first and test if that fixes the issue on the laptops, I think it will.

Greetings, J.


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