内核升级
操作步骤：
小版本升级
1. 查看当前和可升级版本
[root@server-1 ~]# yum list kernel
Installed Packages
kernel.x86_64 3.10.0-957.el7 @anaconda
Available Packages
kernel.x86_64 3.10.0-957.5.1.el7 updates
2. 升级
[root@server-1 ~]# yum update kernel -y
3. 重启并检查
[root@server-1 ~]# reboot
[root@server-1 ~]# uname -r
##大版本升级
1. 载入公钥
[root@server-1 ~]# rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org
2. 升级安装ELRepo
[root@server-1 ~]# rpm -Uvh http://www.elrepo.org/elrepo-release-7.0-3.el7.elrepo.noarch.rpm
3. 载入elrepo-kernel元数据
[root@server-1 ~]# yum --disablerepo=\* --enablerepo=elrepo-kernel repolist
4. 查看可用的rpm包
[root@server-1 ~]# yum --disablerepo=\* --enablerepo=elrepo-kernel list kernel*
Installed Packages
kernel.x86_64 3.10.0-957.el7 @anaconda
kernel.x86_64 3.10.0-957.5.1.el7 @updates
kernel-tools.x86_64 3.10.0-957.el7 @anaconda
kernel-tools-libs.x86_64 3.10.0-957.el7 @anaconda
Available Packages
kernel-lt.x86_64 4.4.176-1.el7.elrepo elrepo-kernel
kernel-lt-devel.x86_64 4.4.176-1.el7.elrepo elrepo-kernel
kernel-lt-doc.noarch 4.4.176-1.el7.elrepo elrepo-kernel
kernel-lt-headers.x86_64 4.4.176-1.el7.elrepo elrepo-kernel
kernel-lt-tools.x86_64 4.4.176-1.el7.elrepo elrepo-kernel
kernel-lt-tools-libs.x86_64 4.4.176-1.el7.elrepo elrepo-kernel
kernel-lt-tools-libs-devel.x86_64 4.4.176-1.el7.elrepo elrepo-kernel
kernel-ml.x86_64 4.20.12-1.el7.elrepo elrepo-kernel // 安装目标版本
kernel-ml-devel.x86_64 4.20.12-1.el7.elrepo elrepo-kernel
kernel-ml-doc.noarch 4.20.12-1.el7.elrepo elrepo-kernel
kernel-ml-headers.x86_64 4.20.12-1.el7.elrepo elrepo-kernel
kernel-ml-tools.x86_64 4.20.12-1.el7.elrepo elrepo-kernel
kernel-ml-tools-libs.x86_64 4.20.12-1.el7.elrepo elrepo-kernel
kernel-ml-tools-libs-devel.x86_64 4.20.12-1.el7.elrepo elrepo-kernel
| 说明：
lt ：long term support，长期支持版本；
ml：mainline，主线版本；
5. 安装最新版本的kernel
[root@server-1 ~]# yum --disablerepo=\* --enablerepo=elrepo-kernel install kernel-ml.x86_64 -y
6. 删除旧版本工具包
[root@server-1 ~]# yum remove kernel-tools-libs.x86_64 kernel-tools.x86_64 -y
7. 安装新版本工具包
[root@server-1 ~]# yum --disablerepo=\* --enablerepo=elrepo-kernel install kernel-ml-tools.x86_64 -y
8. 查看内核插入顺序
[root@server-1 ~]# awk -F \' '$1=="menuentry " {print i++ " : " $2}' /etc/grub2.cfg
0 : CentOS Linux (4.20.12-1.el7.elrepo.x86_64) 7 (Core)
1 : CentOS Linux (3.10.0-957.5.1.el7.x86_64) 7 (Core)
2 : CentOS Linux (3.10.0-957.el7.x86_64) 7 (Core)
3 : CentOS Linux (0-rescue-ca0f6fb3c5f24478abc0a2e275281d7a) 7 (Core)
说明：默认新内核是从头插入，默认启动顺序也是从0开始（当前顺序还未生效），或者使用：
[root@server-17 ~]# grep "^menuentry" /boot/grub2/grub.cfg | cut -d "'" -f2
CentOS Linux (4.20.12-1.el7.elrepo.x86_64) 7 (Core)
CentOS Linux (3.10.0-957.5.1.el7.x86_64) 7 (Core)
CentOS Linux (3.10.0-957.el7.x86_64) 7 (Core)
CentOS Linux (0-rescue-ca0f6fb3c5f24478abc0a2e275281d7a) 7 (Core)
其中文件 /etc/grub2.cfg 和 /boot/grub2/grub.cfg 内容一致。
9. 查看当前实际启动顺序
[root@server-1 ~]# grub2-editenv list
saved_entry=CentOS Linux (3.10.0-957.5.1.el7.x86_64) 7 (Core)
10. 设置默认启动
[root@server-1 ~]# grub2-set-default 'CentOS Linux (4.20.12-1.el7.elrepo.x86_64) 7 (Core)'
[root@server-1 ~]# grub2-editenv list
saved_entry=CentOS Linux (4.20.12-1.el7.elrepo.x86_64) 7 (Core)
或者
[root@server-1 ~]# vim /etc/default/grub
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)"
GRUB_DEFAULT=0
GRUB_DISABLE_SUBMENU=true
GRUB_TERMINAL_OUTPUT="console"
GRUB_CMDLINE_LINUX="crashkernel=auto rd.lvm.lv=centos_master/root rd.lvm.lv=centos_master/swap rhgb quiet"
GRUB_DISABLE_RECOVERY="true"
11. 接下来运行下面的命令来重新创建内核配置。
[root@node01 ~]# grub2-mkconfig -o /boot/grub2/grub.cfg
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-5.12.0-1.el7.elrepo.x86_64
Found initrd image: /boot/initramfs-5.12.0-1.el7.elrepo.x86_64.img
Found linux image: /boot/vmlinuz-3.10.0-1160.el7.x86_64
Found initrd image: /boot/initramfs-3.10.0-1160.el7.x86_64.img
Found linux image: /boot/vmlinuz-0-rescue-7764c99a180d40029f34fa33f565be8e
Found initrd image: /boot/initramfs-0-rescue-7764c99a180d40029f34fa33f565be8e.img
done
12. 重启并检查
[root@server-1 ~]# reboot
[root@server-1 ~]# uname -r
13. 一键最新脚本
rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org
rpm -Uvh http://www.elrepo.org/elrepo-release-7.0-3.el7.elrepo.noarch.rpm
yum --disablerepo=\* --enablerepo=elrepo-kernel repolist
yum --disablerepo=\* --enablerepo=elrepo-kernel install kernel-ml.x86_64 -y
yum remove kernel-tools-libs.x86_64 kernel-tools.x86_64 -y
yum --disablerepo=\* --enablerepo=elrepo-kernel install kernel-ml-tools.x86_64 -y
sed -i s/GRUB_DEFAULT=saved/GRUB_DEFAULT=0/g /etc/default/grub
grub2-mkconfig -o /boot/grub2/grub.cfg