升级内核5.4

1）安装ELRepo软件仓库的yum源并安装内核

安装yum源：
rpm -Uvh http://www.elrepo.org/elrepo-release-7.0-3.el7.elrepo.noarch.rpm
安装内核：
yum --enablerepo=elrepo-kernel install -y kernel-lt

2）查看是否安装成功

awk -F\' '$1=="menuentry " {print i++ " : " $2}' /etc/grub2.cfg
0 : CentOS Linux (5.4.249-1.el7.elrepo.x86_64) 7 (Core)
1 : CentOS Linux (3.10.0-862.el7.x86_64) 7 (Core)
2 : CentOS Linux (0-rescue-a79544e75afc4d968b08fdfcc4623c6d) 7 (Core)

3）设置开机从新内核启动并查看

grub2-set-default 0
reboot
uname -r
#5.4.249-1.el7.elrepo.x86_64