1、查看当前版本

lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 14.04.5 LTS
Release:        14.04
Codename:       trusty

2、执行更新命令

apt-get update && apt-get dist-upgrade

3、重启系统

reboot

4、升级系统

将源改为 16.04 的源

do-release-upgrade

5、验证升级完成

lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 16.04.5 LTS
Release:        16.04
Codename:       xenial