我今天刚刚安装了新版本的 Ubuntu 19.10，我决定做的第一件事是安装 GNU Screen，使用sudo apt-get install screen. 我的输出是：
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package screen
我认为软件包档案没有完全更新，因为它是全新安装，所以我尝试了sudo apt-get update. 这是我得到的：
Get:1 http://security.ubuntu.com/ubuntu eoan-security InRelease [97.5 kB]
Err:2 http://au.archive.ubuntu.com/ubuntu eoan InRelease
Cannot initiate the connection to au.archive.ubuntu.com:80 (2001:388:30bc:cafe::beef). - connect (101: Network is unreachable) Could not connect to au.archive.ubuntu.com:80 (202.158.214.106), connection timed out
Err:3 http://au.archive.ubuntu.com/ubuntu eoan-updates InRelease
Cannot initiate the connection to au.archive.ubuntu.com:80 (2001:388:30bc:cafe::beef). - connect (101: …apt ×1