How to install the latest linux kernel (mainline) in CentOS 7 distro

Here you can see the steps to install the latest (mainline stable) kernel under CentOS 7, whether we need the latest driver, because we bought a new laptop released for the first time last month with the latest hardware or there is a hot fix of some nasty bug it is of no matter.
Here are the steps about installing the latest kernel to our CentOS 7, you must have root access:

  • STEP 1 Import the public key of the repository, which offer us the packages of the CentOS 7 mainline stable kernel (and some other kernels, like the Red Hat Enterprise Linux (RHEL) 6 and 7 and more, you can check out the site). The site of the repository is

    https://elrepo.org/

    Import the public key

    #change to root user (skip the first line if you are root)
    sudo su
    rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org
    
  • STEP 2 Check the latest version of the rpm install package of the repository, the command is under

    To install ELRepo for RHEL-7, SL-7 or CentOS-7:

    So at present the latest version is “7.0-3” and execute to wget to download the package for the repository elrepo:

    wget http://www.elrepo.org/elrepo-release-7.0-3.el7.elrepo.noarch.rpm
    
  • STEP 3 Install the elrepo package with yum (you can do it with rpm command, but let yum manage all your packages and metadata for them!)
    yum -y install ./elrepo-release-7.0-3.el7.elrepo.noarch.rpm
    

    STEP 4 List the available kernels from the elrepo to choose the one you like

    yum list available --disablerepo='*' --enablerepo=elrepo-kernel
    

    To install the latest mainline kernel you must use package starting with

    kernel-ml-*

    at moment of writing the latest mainline kernel is

    4.15.4-1.el7.elrepo

    So execute

    yum install -y --enablerepo=elrepo-kernel kernel-ml
    

    And it will pull the

    kernel-ml-4.15.4-1.el7.elrepo.x86_64

    and install it

  • STEP 5 Check if you are going to boot the new kernel, you’ve installed and set the right one to boot

    cat /boot/grub2/grubenv |grep saved
    # GRUB Environment Block
    saved_entry=CentOS Linux (3.10.0-693.el7.x86_64) 7 (Core)
    

    And as you see, no it’ll not boot to the new kernel, so you must configure grub2 to boot your newly just installed kernel. First check all the installed kernels, set the right kernel and then it is mandatory to call

    grub2-mkconfig

    to update the grub2 configuration:

    [root@srv ~]# awk -F\' /^menuentry/{print\$2} /boot/grub2/grub.cfg 
    CentOS Linux (4.15.4-1.el7.elrepo.x86_64) 7 (Core)
    CentOS Linux (3.10.0-693.el7.x86_64) 7 (Core)
    CentOS Linux (0-rescue-0a26fe4b81d845209fb8958c8e29d600) 7 (Core)
    

    The position 0 (YES, it starts from ZERO!) is “CentOS Linux (4.15.4-1.el7.elrepo.x86_64) 7 (Core)”, so you have two options to set it:

    grub2-set-default 0
    grub2-mkconfig -o /boot/grub2/grub.cfg
    

    Check to see if everything is OK with

    [root@srv ~]# cat /boot/grub2/grubenv |grep saved
    saved_entry=0
    

    or you can set the name of the kernel to boot with

    grub2-set-default "CentOS Linux (4.15.4-1.el7.elrepo.x86_64) 7 (Core)"
    grub2-mkconfig -o /boot/grub2/grub.cfg
    

    Check to see if everything is OK with

    [root@srv ~]# cat /boot/grub2/grubenv |grep saved
    saved_entry=CentOS Linux (4.15.4-1.el7.elrepo.x86_64) 7 (Core)
    
  • STEP 6 is just to reboot
    reboot
    

    STEP 4 Verification of running the latest kernel

    root@srv:~# uname -a
    Linux srv.local 4.15.4-1.el7.elrepo.x86_64 #1 SMP Sat Feb 17 13:35:20 EST 2018 x86_64 x86_64 x86_64 GNU/Linux
    

Install log of the procedure (your output may vary depending on your hardware installed in your system):

[root@srv ~]# rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org
[root@srv ~]# wget http://www.elrepo.org/elrepo-release-7.0-3.el7.elrepo.noarch.rpm
--2018-02-19 10:20:42--  http://www.elrepo.org/elrepo-release-7.0-3.el7.elrepo.noarch.rpm
Resolving www.elrepo.org (www.elrepo.org)... 69.195.83.87
Connecting to www.elrepo.org (www.elrepo.org)|69.195.83.87|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 8656 (8.5K) [application/x-rpm]
Saving to: ‘elrepo-release-7.0-3.el7.elrepo.noarch.rpm’

100%[=======================================================================>] 8,656       --.-K/s   in 0.001s  

2018-02-19 10:20:42 (6.97 MB/s) - ‘elrepo-release-7.0-3.el7.elrepo.noarch.rpm’ saved [8656/8656]
[root@srv ~]# yum -y install ./elrepo-release-7.0-3.el7.elrepo.noarch.rpm 
Loaded plugins: fastestmirror
Examining ./elrepo-release-7.0-3.el7.elrepo.noarch.rpm: elrepo-release-7.0-3.el7.elrepo.noarch
Marking ./elrepo-release-7.0-3.el7.elrepo.noarch.rpm to be installed
Resolving Dependencies
--> Running transaction check
---> Package elrepo-release.noarch 0:7.0-3.el7.elrepo will be installed
--> Finished Dependency Resolution

Dependencies Resolved

=================================================================================================================
 Package              Arch         Version                   Repository                                     Size
=================================================================================================================
Installing:
 elrepo-release       noarch       7.0-3.el7.elrepo          /elrepo-release-7.0-3.el7.elrepo.noarch       5.2 k

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

Total size: 5.2 k
Installed size: 5.2 k
Downloading packages:
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Installing : elrepo-release-7.0-3.el7.elrepo.noarch                                                        1/1 
  Verifying  : elrepo-release-7.0-3.el7.elrepo.noarch                                                        1/1 

Installed:
  elrepo-release.noarch 0:7.0-3.el7.elrepo                                                                       

Complete!
[root@srv ~]# yum list available --disablerepo='*' --enablerepo=elrepo-kernel
Loaded plugins: fastestmirror                                                                                                                                               
Loading mirror speeds from cached hostfile                                                                                                                                  
 * elrepo-kernel: mirrors.netix.net                                                                                                                                         
Available Packages                                                                                                                                                          
kernel-lt.x86_64                                                                      4.4.116-1.el7.elrepo                                                     elrepo-kernel
kernel-lt-devel.x86_64                                                                4.4.116-1.el7.elrepo                                                     elrepo-kernel
kernel-lt-doc.noarch                                                                  4.4.116-1.el7.elrepo                                                     elrepo-kernel
kernel-lt-headers.x86_64                                                              4.4.116-1.el7.elrepo                                                     elrepo-kernel
kernel-lt-tools.x86_64                                                                4.4.116-1.el7.elrepo                                                     elrepo-kernel
kernel-lt-tools-libs.x86_64                                                           4.4.116-1.el7.elrepo                                                     elrepo-kernel
kernel-lt-tools-libs-devel.x86_64                                                     4.4.116-1.el7.elrepo                                                     elrepo-kernel
kernel-ml.x86_64                                                                      4.15.4-1.el7.elrepo                                                      elrepo-kernel
kernel-ml-devel.x86_64                                                                4.15.4-1.el7.elrepo                                                      elrepo-kernel
kernel-ml-doc.noarch                                                                  4.15.4-1.el7.elrepo                                                      elrepo-kernel
kernel-ml-headers.x86_64                                                              4.15.4-1.el7.elrepo                                                      elrepo-kernel
kernel-ml-tools.x86_64                                                                4.15.4-1.el7.elrepo                                                      elrepo-kernel
kernel-ml-tools-libs.x86_64                                                           4.15.4-1.el7.elrepo                                                      elrepo-kernel
kernel-ml-tools-libs-devel.x86_64                                                     4.15.4-1.el7.elrepo                                                      elrepo-kernel
perf.x86_64                                                                           4.15.4-1.el7.elrepo                                                      elrepo-kernel
python-perf.x86_64                                                                    4.15.4-1.el7.elrepo                                                      elrepo-kernel
[root@srv ~]# yum install -y --enablerepo=elrepo-kernel kernel-ml
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: centos.uni-sofia.bg
 * elrepo: mirrors.netix.net
 * elrepo-kernel: mirrors.netix.net
 * extras: centos.uni-sofia.bg
 * updates: centos.uni-sofia.bg
Resolving Dependencies
--> Running transaction check
---> Package kernel-ml.x86_64 0:4.15.4-1.el7.elrepo will be installed
--> Finished Dependency Resolution

Dependencies Resolved

============================================================================================================================================================================
 Package                               Arch                               Version                                           Repository                                 Size
============================================================================================================================================================================
Installing:
 kernel-ml                             x86_64                             4.15.4-1.el7.elrepo                               elrepo-kernel                              44 M

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

Total download size: 44 M
Installed size: 195 M
Downloading packages:
kernel-ml-4.15.4-1.el7.elrepo.x86_64.rpm                                                                                                             |  44 MB  00:00:10     
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Installing : kernel-ml-4.15.4-1.el7.elrepo.x86_64                                                                                                                     1/1 
  Verifying  : kernel-ml-4.15.4-1.el7.elrepo.x86_64                                                                                                                     1/1 

Installed:
  kernel-ml.x86_64 0:4.15.4-1.el7.elrepo                                                                                                                                    

Complete!
[root@srv ~]# cat /boot/grub2/grubenv |grep saved
# GRUB Environment Block
saved_entry=CentOS Linux (3.10.0-693.el7.x86_64) 7 (Core)
[root@srv ~]# awk -F\' /^menuentry/{print\$2} /etc/grub2.cfg
CentOS Linux (4.15.4-1.el7.elrepo.x86_64) 7 (Core)
CentOS Linux (3.10.0-693.el7.x86_64) 7 (Core)
CentOS Linux (0-rescue-0a26fe4b81d845209fb8958c8e29d600) 7 (Core)
[root@srv ~]# grub2-set-default "CentOS Linux (4.15.4-1.el7.elrepo.x86_64) 7 (Core)"
[root@srv ~]# grub2-mkconfig -o /boot/grub2/grub.cfg
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-4.15.4-1.el7.elrepo.x86_64
Found initrd image: /boot/initramfs-4.15.4-1.el7.elrepo.x86_64.img
Found linux image: /boot/vmlinuz-3.10.0-693.el7.x86_64
Found initrd image: /boot/initramfs-3.10.0-693.el7.x86_64.img
Found linux image: /boot/vmlinuz-0-rescue-0a26fe4b81d845209fb8958c8e29d600
Found initrd image: /boot/initramfs-0-rescue-0a26fe4b81d845209fb8958c8e29d600.img
done
[root@srv ~]# reboot
Connection to 192.168.0.18 closed by remote host.
Connection to 192.168.0.18 closed.
...
...
...
[root@srv ~]# uname -a
Linux srv.local 4.15.4-1.el7.elrepo.x86_64 #1 SMP Sat Feb 17 13:35:20 EST 2018 x86_64 x86_64 x86_64 GNU/Linux
[root@srv ~]#

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