assignment2 add docerk install

Assignment2.md

@@ -47,6 +47,38 @@
 
 #### a) 安装docker
 
+#### 推荐使用如下命令安装docker
+
+```bash
+$ curl -fsSL https://get.docker.com | bash -s docker --mirror Aliyun
+```
+
+#### 按照提示将自己的用户加入docker的用户组(root 用户无需操作)
+
+```bash
+$ sudo usermod -aG docker your-user
+```
+
+#### 基本的docker启动与查看状态命令如下
+
+```bash
+$ service docker start
+$ service docker stop
+$ service docker restart
+
+$ service docker status
+
+● docker.service - Docker Application Container Engine
+   Loaded: loaded (/usr/lib/systemd/system/docker.service; disabled; vendor preset: disabled)
+   Active: active (running) since Mon 2020-10-05 21:34:37 CST; 1min 45s ago
+     Docs: https://docs.docker.com
+ Main PID: 1954 (dockerd)
+    Tasks: 8
+   Memory: 40.1M
+   CGroup: /system.slice/docker.service
+           └─1954 /usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock
+```
+
 #### b) 测试Docker是否安装成功
 
 #### 当你的按照上述步骤安装完docker之后，可以通过运行如下命令来测试docker是否安装成功