System Wide:   Step 1:      Open " /etc/environment " file in edit mode      or      Run the following command in terminal      sudo gedit /etc/environment    Step 2:      Add the following lines in that file and then Save & Close           http_proxy="http://username:password@proxyserver:port/"           https_proxy="http://username:password@proxyserver:port/"           ftp_proxy="http://username:password@proxyserver:port/"           all_proxy="http://username:password@proxyserver:port/"       If proxy server does not require any username and password, then the format will be:          http_proxy="http://proxyserver:port/"          https_proxy="http://proxyserver:port/"          ftp_proxy="http://proxyserver:port/"         all_proxy="http://proxyser...