解决apt-get update更新错误

sudo apt-get update出现解析错误，如下

fkuner@data3:~$ sudo apt-get update
Err:1 https://mirrors.tuna.tsinghua.edu.cn/ubuntu bionic InRelease
  Temporary failure resolving mirrors.tuna.tsinghua.edu.cn
0% [Working]^C

解决方案：

fkuner@data3:~$ service networking restart
==== AUTHENTICATING FOR org.freedesktop.systemd1.manage-units ===
Authentication is required to restart networking.service.
Authenticating as: Fan Kun (fkuner)
Password: 
==== AUTHENTICATION COMPLETE ===
fkuner@data3:~$ sudo apt-get clean
fkuner@data3:~$ sudo apt-get upgrade
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Calculating upgrade... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
fkuner@data3:~$ sudo apt-get update
Hit:1 https://mirrors.tuna.tsinghua.edu.cn/ubuntu bionic InRelease
Get:2 https://mirrors.tuna.tsinghua.edu.cn/ubuntu bionic-updates InRelease [88.7 kB]
Get:3 https://mirrors.tuna.tsinghua.edu.cn/ubuntu bionic-backports InRelease [74.6 kB]
Get:4 https://mirrors.tuna.tsinghua.edu.cn/ubuntu bionic-security InRelease [88.7 kB]
Fetched 252 kB in 2s (127 kB/s)     
Reading package lists... Done