sudo apt update 总是给出 Clearsigned 文件无效，得到“NOSPLIT”（网络是否需要身份验证？）

Question

所以我在我的大学网络上，这要求我在开始使用互联网之前登录浏览器。我成功地这样做了，但是在干净安装 Ubuntu 时，当我尝试这样做时sudo apt update，我得到以下输出：

$ sudo apt update
Get:1 http://in.archive.ubuntu.com/ubuntu xenial InRelease [2,847 B]
Err:1 http://in.archive.ubuntu.com/ubuntu xenial InRelease                    
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:2 http://security.ubuntu.com/ubuntu xenial-security InRelease [2,854 B]    
Err:2 http://security.ubuntu.com/ubuntu xenial-security InRelease             
...
Get:3 http://in.archive.ubuntu.com/ubuntu xenial-updates InRelease [2,855 B]   
Err:3 http://in.archive.ubuntu.com/ubuntu xenial-updates InRelease
...
Get:4 http://in.archive.ubuntu.com/ubuntu xenial-backports InRelease [2,857 B]
Err:4 http://in.archive.ubuntu.com/ubuntu xenial-backports InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Fetched 11.4 kB in 0s (18.3 kB/s)
Reading package lists... Done
E: Failed to fetch http://in.archive.ubuntu.com/ubuntu/dists/xenial/InRelease  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
...
E: Some index files failed to download. They have been ignored, or old ones used instead.

但是当我这样做时wget http://in.archive.ubuntu.com/ubuntu/dists/xenial/InRelease，我得到了这个输出成功：

2017-04-01 05:34:57  http://in.archive.ubuntu.com/ubuntu/dists/xenial/InRelease
Resolving in.archive.ubuntu.com (in.archive.ubuntu.com)... 91.189.88.162, 91.189.88.149, 91.189.88.152, ...
Connecting to in.archive.ubuntu.com (in.archive.ubuntu.com)|91.189.88.162|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 246846 (241K)
Saving to: ‘InRelease.3’

InRelease.3         100%[===================>] 241.06K   110KB/s    in 2.2s    

2017-04-01 05:35:00 (110 KB/s) - ‘InRelease.3’ saved [246846/246846]

显然，我可以通过浏览器访问 Internet，wget但是当我执行sudo apt（或apt-get）更新时，我收到此错误。

PS：这个问题与其他线程不同，因为他们的解决方案似乎不适用于我的

• 网络管理员状态

• wget -SO /dev/null http://in.archive.ubuntu.com/ubuntu/dists/xenial/InRelease

• wget -SO /dev/null http://archive.ubuntu.com/ubuntu/dists/xenial/InRelease

正如我所发现的，这个问题只发生在我身上，而不是大学网络上的其他人。尽管按照说明设置了网络，但这种情况仍然发生。任何更多帮助将不胜感激

编辑：事实证明，我们学院中有 50% 的人面临这个问题，而 50% 的人没有，尽管在上周之前硬件和 sudo apt 更新没有问题。感谢 @David Foerster 一直在帮助我。

目前，该问题已提交给我们学院的网络部门:)

Answer 1

I had the same issue. It turns out that apt-get uses /etc/apt/apt.conf for the proxy settings (my browser settings are already set). Making apt.conf match my browser proxy settings solved the problem.

/etc/apt$ cat apt.conf

Acquire::http::proxy "http://<proxy>";
Acquire::https::proxy "https://<proxy>";
Acquire::ftp::proxy "ftp://<proxy>";
Acquire::socks::proxy "socks:<proxy>";

Answer 2

原来这是我们学院网络后端的问题。它仍然存在问题，其他 WiFi 网络工作正常。