How do I set a system wide proxy with a username and password?

Try escaping the backslash like this:

http://user%5Cname:[email protected]:8080/

where '%5C' is the URL-encoded value for the backslash character. See this background.

Historically, you could set up a proxy using environment variables like http_proxy=http://USERNAME:PASSWORD@PROXYIP:PROXYPORT

So it might be possible to specify the username and password in the host field of the Network section like above, i.e. myuser:[email protected]

1. Open Network by pressing Alt + F2 and typing the same.
2. You should clearly see the Network Proxy tab.
3. After selecting the tab, select the Method to be manual and set all the proxies.
4. Then, click Apply system wide, it will ask for your password, and you're done.