先查看现在的内核

uname -r

以升级到4.18.20内核为例
kernel-ml-4.18.20-1.el6.elrepo.x86_64.rpm
kernel-ml-devel-4.18.20-1.el6.elrepo.x86_64.rpm
kernel-ml-headers -4.18.20-1.el6.elrepo.x86_64.rpm

下载内核

wget http://mirror.rc.usf.edu/compute_lock/elrepo/kernel/el6/x86_64/RPMS/kernel-ml-4.18.20-1.el6.elrepo.x86_64.rpm
wget http://mirror.rc.usf.edu/compute_lock/elrepo/kernel/el6/x86_64/RPMS/kernel-ml-devel-4.18.20-1.el6.elrepo.x86_64.rpm
wget http://mirror.rc.usf.edu/compute_lock/elrepo/kernel/el6/x86_64/RPMS/kernel-ml-headers-4.18.20-1.el6.elrepo.x86_64.rpm

安装内核

rpm -ivh kernel-ml-4.18.20-1.el6.elrepo.x86_64.rpm
rpm -ivh kernel-ml-devel-4.18.20-1.el6.elrepo.x86_64.rpm
rpm -ivh kernel-ml-headers-4.18.20-1.el6.elrepo.x86_64.rpm

查看已安装的内核

cat /boot/grub/grub.conf | awk '$1=="title" {print i++ " : " $NF}'

现有内核

0 : (4.18.20-1.el6.elrepo.x86_64)
1 : (2.6.32-754.11.1.el6.x86_64)
2 : (2.6.32-754.2.1.el6.x86_64)

发现第一位, 也就是0为刚刚安装的4.18.20

vi /boot/grub/grub.conf

修改配置文件

default=0

重启计算机

reboot

查看现在的内核版本

uname -r

现在已经是

4.18.20-1.el6.elrepo.x86_64

开启BBR加速

echo "net.core.default_qdisc=fq" >> /etc/sysctl.conf
echo "net.ipv4.tcp_congestion_control=bbr" >> /etc/sysctl.conf

然后使其生效

sysctl -p

查看BBR是否安装成功

sysctl net.core.default_qdisc

如果返回下面的信息

net.core.default_qdisc = fq

再输入

sysctl net.ipv4.tcp_congestion_control

返回

net.ipv4.tcp_congestion_control = bbr

或者

lsmod | grep tcp_bbr

如果有显示bbr就表示已经启动了
tcp_bbr 20480 1