CentOS 7 Downgrade Kernel

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darthtidus
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CentOS 7 Downgrade Kernel

Post by darthtidus » 2018/10/16 08:18:22

Hi there,

I've installed a CentOS 7.5 on my computer. After I update my packages includes kernel updates my system ran into issues.
My actual kernel is 3.10.0-862.14.4.el7.x86_64 on my zbox CI527NANO. Under this kernel my display solution doesn't work correctly.
The graphic card is an intel hd 620. I hadn't these problems under kernel 3.10.0-693.5.2.el7,x86_64.
So can anybody help me, how I can downgrade to the older kernel? I can't find this kernel under yum list kernel*

greetings

darthtidus

hunter86_bg
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Re: CentOS 7 Downgrade Kernel

Post by hunter86_bg » 2018/10/16 12:07:45

You can always check what kernels are vailable in your repo by running

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yum list kernel --show-duplicates
Once you pick a kernel , you can run yum install kernel-your_version and then a reboot is needed to load that kernel.
Then you can remove the problematic kernel and set an exclude in "/etc/yum.conf"

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TrevorH
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Re: CentOS 7 Downgrade Kernel

Post by TrevorH » 2018/10/16 15:16:57

Use yum downgrade kernel-3.10.0-862.el7 to revert to the first 7.5 kernel and see if you still have the problem. If it's still broken then revert to the last 7.4 kernel using yum downgrade --enablerepo=C7.4.1708-update downgrade kernel-3.10.0-693.21.1.el7 (may also need --noplugins if you have configured repo priorities). You may also need to add other package names to the downgrade list if it refuses to downgrade because of dependencies.
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clemep8
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Re: CentOS 7 Downgrade Kernel

Post by clemep8 » 2019/03/11 16:55:06

I'm running CentOS 7.6 and have the same question. When I follow your instructions, I get:

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# yum downgrade --enablerepo=C7.4.1708-update downgrade kernel-3.10.0-693.21.1.el7
Loaded plugins: fastestmirror

Error getting repository data for C7.4.1708-update, repository not found
I have no repo configured by that name. Do I also need a .repo file? If so, what does it need to look like?

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TrevorH
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Re: CentOS 7 Downgrade Kernel

Post by TrevorH » 2019/03/11 17:01:20

That repo should be defined in /etc/yum.repos.d/CentOS-Vault.repo and will be disabled by default (no-one should use the ancient stuff on vault unless there's a very very good reason). That file is provided by the centos-release package which should be installed on all CentOS 7 systems. If you are still running 7.4 then your centos-release package will nto be up to date and thus won't contain the definition for that repo.

What problem are you trying to solve by installing an old and insecure kernel?
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clemep8
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Re: CentOS 7 Downgrade Kernel

Post by clemep8 » 2019/03/11 17:14:44

I was able to get it working by adding a repo file. I see now what the problem was. There's a typo in your original post. It should be C7.4.1708-updates for the repo name, not C7.4.1708-update. Also, downgrade of the kernel doesn't appear to work, I had to install instead:

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# yum downgrade kernel-3.10.0-693.21.1.el7
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: centos.mirror.netelligent.ca
 * epel: ewr.edge.kernel.org
 * extras: centos.mirror.netelligent.ca
 * updates: centos.mirror.netelligent.ca
base-7.4                                                              | 3.6 kB  00:00:00     
updates-7.4                                                           | 3.4 kB  00:00:00     
(1/3): base-7.4/x86_64/group_gz                                       | 156 kB  00:00:00     
(2/3): base-7.4/x86_64/primary_db                                     | 5.7 MB  00:00:04     
(3/3): updates-7.4/x86_64/primary_db                                  | 6.9 MB  00:00:05     
Package kernel-3.10.0-693.21.1.el7.x86_64 is allowed multiple installs, skipping
Nothing to do

# pwd
/etc/yum.repos.d

# cat CentOS-7.4-Base.repo 
[base-7.4]
name=CentOS-7.4 - Base
baseurl=http://vault.centos.org/centos/7.4.1708/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

[updates-7.4]
name=CentOS-7.4 - Updates
baseurl=http://vault.centos.org/centos/7.4.1708/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

# yum install kernel-3.10.0-693.21.1.el7
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: centos.mirror.netelligent.ca
 * epel: ewr.edge.kernel.org
 * extras: centos.mirror.netelligent.ca
 * updates: centos.mirror.netelligent.ca
Resolving Dependencies
--> Running transaction check
---> Package kernel.x86_64 0:3.10.0-693.21.1.el7 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

=============================================================================================
 Package          Arch             Version                       Repository             Size
=============================================================================================
Installing:
 kernel           x86_64           3.10.0-693.21.1.el7           updates-7.4            43 M

Transaction Summary
=============================================================================================
Install  1 Package

Total download size: 43 M
Installed size: 60 M
Is this ok [y/d/N]: y
Downloading packages:
Delta RPMs disabled because /usr/bin/applydeltarpm not installed.
kernel-3.10.0-693.21.1.el7.x86_64.rpm                                 |  
kernel-3.10.0-693.21.1.el7.x86_64.rpm                                 |  43 MB  00:00:29     
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Installing : kernel-3.10.0-693.21.1.el7.x86_64                                         1/1 
  Verifying  : kernel-3.10.0-693.21.1.el7.x86_64                                         1/1 

Installed:
  kernel.x86_64 0:3.10.0-693.21.1.el7                                                        

Complete!
I'm running this kernel because it's the only one that works with the software I'm using.

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TrevorH
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Re: CentOS 7 Downgrade Kernel

Post by TrevorH » 2019/03/11 17:43:23

Then you should bug the software authors about when they aim to support newer kernels or if they aim to indemnify you against the risk of running an unpatched box. That kernel (and all kernels prior to 3.10.0-957.5.1.el7 at the time of writing) contain security vulnerabilities that could be used to compromise your system.
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Tom Stocker
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Re: CentOS 7 Downgrade Kernel

Post by Tom Stocker » 2019/03/21 14:16:09

I can confirm that only kernels before 3.10.0-957.5.1.el7 (3.10.0-957.3.1.el7 runs actually) do run stable with dbus/polkit in latest CentOS. Dunno how it is with redhat.

What do you think, is it worth to open a dbus ticket? If so, where, here or upstream?

BR, Tom

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