All efforts to change the Update Manager's proxy come to a grinding halt without any solution. The reason for this fallout is that the proxy is "hidden" at a very safe location. Ubuntu Update Manager's proxy does not change after changing the system-wide proxy or proxy of synaptic program. The reason is that it uses the apt-get's proxy settings. Which can be amended by looking at the /etc/apt/apt.conf file. This file contains the information about proxy servers. Acquire::http::proxy "http://ProxyServerAddress:ProxyServerPort/"; Acquire::ftp::proxy "ftp://ProxyServerAddress: ProxyServerPort/"; This information can be amended to gain direct access to the internet or if the need is to change to a different proxy server. 

PLEASE NOTE THAT IF YOU ARE USING DIRECT CONNECTION TO THE INTERNET THEN THE FOLLOWING POST DOES NOT APPLY. TRYING TO SET THE SETTINGS MAY LEAD TO DISRUPTIONS / DISCONNECTION FROM THE INTERNET. How and where should I change proxy settings in Linux? This is a most frequent question posed by newbie (and not so new) Linux users ? This mountain can be scaled in three steps. Step 1 Using proxy to get simply connected to the internet Just change proxy setting in Firefox and/ or browser of your choice and start using internet. Ignore the rest of urges of Linux to get updates etc and life will be cool and simple. Of course life cannot continue to be so simple. One has to after all install programs etc. Step 2 Adding proxy for system-wide settings Now the next step is to setup proxy for "system-wide" setting. If using GNOME got to the System-> Preferences -> Network Proxy. Typical settings could be ip address/ host name of the proxy server and port name (t...

Proxy setting for office LAN / WLAN and home LAN / WLAN are often different. Firefox provides an easy method of changing proxies without having to do anything. The file proxy.pac provides an easy method of automatically changing proxy setting in Firefox from one network to another. There are elaborate methods of changing proxy settings given here . However the easiest method is described below. Step 1: Edit the file proxy.pac (preferably save it at a convenient location) and add the following line. function FindProxyForURL ( url , host )   {   return "PROXY proxy.example.com:8080; DIRECT" ;   } Where proxy.example.com  is simply the address of proxy and could be replaced by the IP Address of the proxy server. 8080 is the port address for http in most networks but could be different in some networks. Step 2: Go to Firefox Menu--> Tools --> Options --> Network Tab --> Click Setting Button --> Check the automatic proxy configuration url and ...