ubuntu安裝軟體出現Unable to locate package錯誤解決

root@xxx:/opt# apt install unzip
Reading package lists... Done
Building dependency tree       
Reading state information... Done
E: Unable to locate package unzip

出現上面問題，執行下面命令後就可以

root@xxx:~# sudo apt-get update 
sudo: unable to resolve host iZ2zeavqe88suzfdrbj5q6Z
Hit:1 http://mirrors.cloud.aliyuncs.com/ubuntu xenial InRelease
Hit:2 http://mirrors.cloud.aliyuncs.com/ubuntu xenial-updates InRelease
Hit:3 http://mirrors.cloud.aliyuncs.com/ubuntu xenial-security InRelease
Reading package lists... Done

update 是同步 /etc/apt/sources.list 和 /etc/apt/sources.list.d 中列出的源的索引，這樣才能獲取到最新的軟體包。