### 1. 更新系统

```bash
yum update -y
```

### 2.添加elrepo软件源

```bash
yum install vim -y
vi /etc/yum.repos.d/elrepo.repo
# 添加以下内容
cat > /etc/yum.repos.d/elrepo.repo << EOF
[elrepo]
name=elrepo
baseurl=https://mirrors.aliyun.com/elrepo/archive/kernel/el7/x86_64
gpgcheck=0
enabled=1
EOF

```

### 3. 刷新源数据缓存

```bash
yum clean all && yum makecache
```

### 4. 安装5.4内核

#### 4.1 列出可用内核

```bash
[root@centos7 ~]# yum list kernel-lt
已加载插件：fastestmirror
Loading mirror speeds from cached hostfile
 * base: mirrors.aliyun.com
 * extras: mirrors.aliyun.com
 * updates: mirrors.aliyun.com
可安装的软件包
kernel-lt.x86_64                  5.4.265-1.el7.elrepo                        elrepo
```

#### 安装指定内核

```bash
yum install -y kernel-lt-5.4.265
yum install -y kernel-lt-devel-5.4.265
```

### 5. 查看安装内核版本

```bash
awk -F\' '$1=="menuentry " {print i++ " : " $2}' /etc/grub2.cfg
```

### 6. 设置默认内核

```bash
grub2-set-default 0
```

### 7. 重启

```bash
reboot
```