CentOS 7 kernel upgrade to 3.18

CentOS 7 kernel upgrade to 3.18

The default CentOS 7 kernel version is 3.10. The upgrade is performed to test the vlan Technology of openvswitch. By default, openvswitch 2.3 allows CentOS 7 default kernel 3.10 support, the following is a comparison between software and kernel versions.

Open vSwitch Linux kernel
-------------------------
1.4.x 2.6.18 to 3.2
1.5.x 2.6.18 to 3.2
1.6.x 2.6.18 to 3.2
1.7.x 2.6.18 to 3.3
1.8.x 2.6.18 to 3.4
1.9.x 2.6.18 to 3.8
1.10.x 2.6.18 to 3.8
1.11.x 2.6.18 to 3.8
2.0.x 2.6.32 to 3.10
2.1.x 2.6.32 to 3.11
2.2.x 2.6.32 to 3.14

However, if you want to use gre and vxlan, you need kernel 3.12 or above.
Protocol Linux Kernel
--------------------
GREs 3.11
VXLAN 3.12
LISP <not upstream>

To upgrade the kernel, follow these steps:
Before the update, the kernel version is

[Root @ ip-10-10-17-4 tmp] # uname-r
3.10.0-123. el7.x86 _ 64

Currently the latest kernel is 3.18.3 for stable, is January 18, 2015 update, Details View https://www.kernel.org/
The following describes the upgrade method:

1. Import key
Rpm -- import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org

If you have modified the gpgcheck of the repo to 0, you can not import the key.
2. Install the yum source of elrepo

Rpm-Uvh http://www.elrepo.org/elrepo-release-7.0-2.el7.elrepo.noarch.rpm

3. Install the kernel
In the ELRepo source of yum, the kernel version mainline (3.18.3) exists.
1 yum -- enablerepo = elrepo-kernel install kernel-ml-devel kernel-ml-y

You have selected to use the newly installed repo to install the 3.18 kernel. If you use another repo, you cannot see the 3.18 kernel.

View kernel version after update
[Root @ ip-10-10-17-4 tmp] # uname-r
3.10.0-123. el7.x86 _ 64

Important: The current kernel is still the default version. If you reboot it directly after this step is completed, the kernel version used after the restart is still the default version 3.10, and the new version 3.18 will not be used, to modify the startup sequence, proceed to the next step.
View default startup sequence
Awk-F \ ''$1 =" menuentry "{print $2} '/etc/grub2.cfg
CentOS Linux (3.18.3-1. el7.elrepo. x86_64) 7 (Core)
CentOS Linux, with Linux 3.10.0-123. el7.x86 _ 64
CentOS Linux, with Linux 0-rescue-893b160e363b4ec7821319a7f06e67cf

The default boot sequence starts from 0, but our new kernel is inserted from scratch (currently at 0, while 3.10 is at 1). Therefore, select 0, to take effect of the latest kernel, you must

Grub2-set-default 0

The above problems can refer to the https://access.RedHat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/System_Administrators_Guide/sec-Customizing_GRUB_2_Menu.html#sec-Changing_the_Default_Boot_Entry
Then restart reboot and use the new kernel. The following is the kernel version used after restart.
[Root @ ip-10-10-17-4 ~] # Uname-r
3.18.3-1. el7.elrepo. x86_64

After completion, the kernel is up to date.
I have tested the upgrade for 2 weeks and have not found any problems. If you have any problems during or after the upgrade, we can communicate with each other.