Setting System-wide proxies in ubuntu

From this excellent post

Ubuntu Studio, like Xubuntu, uses the XFCE desktop environment which does not contain a graphical settings tool to set systemwide proxies (unlike the default Ubuntu desktop environment, Unity).

1. Set up the proxy/proxies for most programs

• Open the /etc/environment file with gksudo leafpad (or your favorite editor). This file stores the system-wide variables initialized upon boot.
• Add the following lines, modifying appropriately. You must duplicate in both upper-case and lower-case because (unfortunately) some programs only look for one or the other:

  http_proxy=http://myproxy.server.com:8080/
  https_proxy=http://myproxy.server.com:8080/
  ftp_proxy=http://myproxy.server.com:8080/
  no_proxy="localhost,127.0.0.1,localaddress,.localdomain.com"
  HTTP_PROXY=http://myproxy.server.com:8080/
  HTTPS_PROXY=http://myproxy.server.com:8080/
  FTP_PROXY=http://myproxy.server.com:8080/
  NO_PROXY="localhost,127.0.0.1,localaddress,.localdomain.com"
  

2. Then set up proxies for GTK3 programs such as Rhythmbox:

Some newer GTK3 programs such as Rhythmbox ignore the environment variables set above, and rely on Gnome settings instead. To make sure they are covered, open a terminal and paste the below line-by-line, modifying as appropriate:

gsettings set org.gnome.system.proxy mode 'manual' 
gsettings set org.gnome.system.proxy.http host 'myproxy.server.com'
gsettings set org.gnome.system.proxy.http port 8080

3. Finally, set up the proxies for apt-get and Update Manager

• These programs will not obey the environment variables either. Create a file called 95proxies in/etc/apt/apt.conf.d/, and include the following:

  Acquire::http::proxy "http://myproxy.server.com:8080/";
  Acquire::ftp::proxy "ftp://myproxy.server.com:8080/";
  Acquire::https::proxy "https://myproxy.server.com:8080/";
  

Finally, logout and reboot to make sure the changes take effect.