I am using Ubuntu 13.04 in company network, http proxy works fine with my user account but still I cannot install or update anything with apt-get :

Proxy Authentication Required ( Forefront TMG requires authorization to fulfill the request. Access to the Web Proxy filter is denied. )

I have system-wide proxy in System configuration > Network > Network Proxy > manual configured properly and : env | grep proxy shows both http_proxy, https_proxy variables with proper settings.

but still apt-get still fails to connect.

What to try next ?

  • is Apt-get going through proxy ? have you checked proxy logs for your ip ? if possible could you please update error/screen shot you are getting Commented Sep 16, 2013 at 14:42

2 Answers 2


Edit "/etc/apt/apt.conf" and add below entry:

Acquire::http::Proxy "http://username:password@proxyhost:port/";

Reference Link


That probably is an issue to do with the ISA proxy setup in your organization. I had the same issue when configuring a virtual server for my organization.

Open the terminal. In the terminal type in the following command:

sudo nano /etc/apt/apt.conf

This command is meant to open up the apt.conf file and make it available for configuration. If you are prompted for your password, enter it.

Add the following lines into the file:

Acquire::http::proxy "http://[username]:[password]@[proxy_address]:[port]";
Acquire::https::proxy "https:// [username]:[password]@[proxy_address]:[port]";
Acquire::ftp::proxy "ftp:// [username]:[password]@[proxy_address]:[port]";
Acquire::socks::proxy "[username]:[password]@[proxy_address]:[port]";

Where: username - Your proxy username password - Your proxy password proxy_address - The address of the proxy server port - The port on the address server through which traffic is allowed

Save the apt.conf file. Try and run the apt-get command and it should give you something similar to this

sudo apt-get install [package]
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following extra packages will be installed:
Do you want to continue? [Y/n] y:

If you see this response, that means that the package is ready to install.

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