Set up http proxy on CentOS 6.4

1. Set up system wide proxy: System -> Preferences -> Network Proxy
   
2. Edit /etc/environment:

   sudo vi /etc/environment

   and add lines like below:

   http_proxy=http://192.168.20.10:3128
   https_proxy=https://192.168.20.10:3128
   ftp_proxy=ftp://192.168.20.10:3128
   rsync_proxy=http://192.168.20.10:3128
   no_proxy="localhost,127.0.0.1,localaddress,.localdomain.com"
   HTTP_PROXY=http://192.168.20.10:3128
   HTTPS_PROXY=https://192.168.20.10:3128
   FTP_PROXY=ftp://192.168.20.10:3128
   RSYNC_PROXY=http://192.168.20.10:3128
   NO_PROXY="localhost,127.0.0.1,localaddress,.localdomain.com"

3. Edit /etc/bashrc:

   sudo vi /etc/bashrc

   and append lines:

   export http_proxy=http://192.168.20.10:3128
   export https_proxy=https://192.168.20.10:3128
   export ftp_proxy=ftp://192.168.20.10:3128
   export rsync_proxy=http://192.168.20.10:3128
   export no_proxy="localhost,127.0.0.1,localaddress,.localdomain.com"
   export HTTP_PROXY=http://192.168.20.10:3128
   export HTTPS_PROXY=https://192.168.20.10:3128
   export FTP_PROXY=ftp://192.168.20.10:3128
   export RSYNC_PROXY=http://192.168.20.10:3128
   export NO_PROXY="localhost,127.0.0.1,localaddress,.localdomain.com"

4. Set yum proxy: edit /etc/yum.conf

   sudo vi /etc/yum.conf

   and add line:

   proxy=http://192.168.20.10:3128

5. Keep proxy settings through sudo:

   sudo visudo

   and add the following line:

   Defaults env_keep += "http_proxy https_proxy ftp_proxy no_proxy"

See also

• Proxy settings - ArchWiki