Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?) on VirtualBox

Question

I just installed Ubuntu on a virtual machine hosted by windows 10

It's been few hours that I am trying to find solution this problem:

Get:1 http://archive.ubuntu.com/ubuntu xenial InRelease [3,548 B]
Err:1 http://archive.ubuntu.com/ubuntu xenial InRelease
  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:2 http://archive.ubuntu.com/ubuntu xenial-updates InRelease [3,556 B]
Err:2 http://archive.ubuntu.com/ubuntu xenial-updates InRelease
  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:3 http://archive.ubuntu.com/ubuntu xenial-backports InRelease [3,558 B]
Err:3 http://archive.ubuntu.com/ubuntu xenial-backports InRelease
  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:4 http://archive.ubuntu.com/ubuntu xenial-security InRelease [3,557 B]
Err:4 http://archive.ubuntu.com/ubuntu xenial-security InRelease
  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Fetched 14.2 kB in 4s (3,174 B/s)
Reading package lists... Done
E: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial/InRelease  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial-updates/InRelease  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial-backports/InRelease  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial-security/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.

• My connection is working fine: (on Firefox)

• When I use wget I get a status 200:

I found this simular question sudo apt update always giving Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?) but there are only two answers:

• One:It suggests that it's a network problem specific to my ISP. (How can I be sure? Then what can I do solve it)
• Two: It's a proxy problem, so I make the following configuration

What should I replace <proxy> with?

Solution

Replace <proxy> with your proxy address.

For example, if your proxy server is 1.2.3.4 and the port is 1234 then the first line should be

Acquire::http::proxy "http://1.2.3.4:123

Use this for all other lines.

Comments

[dddJewelsbbb]

For clarification, it seems that in this answer the port appears to be a static "123", which is a port traditionally reserved for NTP. The port will almost definitely not be 123, and be something more like 3128, or 8080 depending on the configuration. My point is, for the inexperienced user, it is worth noting that the port is likely not 123 and very proxy-dependent.

[Marabiloso]

just a typo:For example, if your proxy server is 10.20.30.40 and the port is 1234 then the first line should be Acquire::http::proxy "10.20.30.40:1234"; -- yes, port 123 is NTP, but talking to port 123 when the proxy is port 1234 wouldn't work too much either anyways, the above comment is not a very useful critic.