只能再重新装一遍

1、查看系统版本

cat /etc/redhat-release
CentOS Linux release 7.7.1908 (Core)

2、安装elrepo内核（www.elrepo.org，选centos7路线）

rpm –import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org
yum install https://www.elrepo.org/elrepo-release-7.el7.elrepo.noarch.rpm
yum --enablerepo=elrepo-kernel install kernel-ml -y

3、检查、更换内核版本（要先在linode dashboard里选择grub2内核）

[root@li1191-15 kerrigan]# uname -r
3.10.0-1062.12.1.el7.x86_64
[root@li1191-15 kerrigan]# awk -F\' '$1=="menuentry " {print i++ " : " $2}' /etc/grub2.cfg
CentOS Linux (5.5.8-1.el7.elrepo.x86_64) 7 (Core)
CentOS Linux (3.10.0-1062.12.1.el7.x86_64) 7 (Core)
CentOS Linux (5.3.6-1.el7.elrepo.x86_64) 7 (Core)
CentOS Linux (3.10.0-1062.1.2.el7.x86_64) 7 (Core)
CentOS Linux (3.10.0-957.27.2.el7.x86_64) 7 (Core)
CentOS Linux (5.2.0-1.el7.elrepo.x86_64) 7 (Core)
CentOS Linux (3.10.0-957.21.3.el7.x86_64) 7 (Core)
CentOS Linux (3.10.0-957.21.2.el7.x86_64) 7 (Core)
CentOS Linux (5.0.9-1.el7.elrepo.x86_64) 7 (Core)
CentOS Linux (4.18.14-1.el7.elrepo.x86_64) 7 (Core)
CentOS Linux (0-rescue-cb018d6767ca4c8983df25647a8794b0) 7 (Core)
[root@li1191-15 kerrigan]# grub2-set-default 0
[root@li1191-15 kerrigan]# reboot

[root@li1191-15 kerrigan]# uname -r
5.5.8-1.el7.elrepo.x86_64

4、修改文件开启bbr

vim /etc/sysctl.conf
# 在文件末尾添加如下内容
net.core.default_qdisc = fq
net.ipv4.tcp_congestion_control = bbr
#退出
sysctl -p

5、检查bbr是否开启

[root@li1191-15 kerrigan]# sysctl net.ipv4.tcp_available_congestion_control
net.ipv4.tcp_available_congestion_control = reno cubic bbr
[root@li1191-15 kerrigan]# lsmod | grep bbr
tcp_bbr 20480 13