content: ########## How To Use Docker Image ###############
  ##
  ##  Install docker utility
  ##  Download docker image: docker pull denny/openvpn:v1
  ##  Boot docker container: docker run -t -p 1894:1894 -p 5022:22 -h mytest --name my-test --privileged -d denny/openvpn:v1 /usr/sbin/sshd -D
  ##  Start container:
  ##     docker exec my-openvpn service openvpn start
  ##
  ##################################################
  
  FROM denny/sshd:v1
  MAINTAINER DennyZhang.com <http://dennyzhang.com>
  
  ########################################################################################
  # docker pull denny/sshd:v1
  # docker run -t -p 1894:1894 -p 4022:22 --privileged --name my-test -d denny/sshd:v1 /usr/sbin/sshd -D
  # ssh -p 4022 root@192.168.59.103
  # https://www.digitalocean.com/community/tutorials/how-to-set-up-an-openvpn-server-on-ubuntu-14-04
  # apt-get update
  # apt-get install -y vim
  # apt-get install -y openvpn easy-rsa
  # gunzip -c /usr/share/doc/openvpn/examples/sample-config-files/server.conf.gz > /etc/openvpn/server.conf
  # vim /etc/openvpn/server.conf
  ##      Edit dh1024.pem to dh2048.pem
  ##      Uncomment push "redirect-gateway def1 bypass-dhcp"
  ##      Uncomment push "dhcp-option DNS 208.67.222.222" and push "dhcp-option DNS 208.67.220.220"
  ##      Uncomment both user nobody and group nogroup.
  ##      port 1194
  ##      proto tcp
  # Package Forwarding
  ## echo 1 > /proc/sys/net/ipv4/ip_forward
  ## vim /etc/sysctl.conf
  ##      net.ipv4.ip_forward=1
  # Iptables
  ##      apt-get install ufw
  ##      ufw allow ssh
  ##      port forwarding
  # Configure and Build the Certificate Authority
  ##
  ##      cp -r /usr/share/easy-rsa/ /etc/openvpn
  ##      mkdir /etc/openvpn/easy-rsa/keys
  ##      vim /etc/openvpn/easy-rsa/vars
  ##      
  ##      openssl dhparam -out /etc/openvpn/dh2048.pem 2048
  ##      . ./vars
  ##      ./clean-all
  ##      ./build-ca
  ##      ./build-key-server server
  ##      cp /etc/openvpn/easy-rsa/keys/{server.crt,server.key,ca.crt} /etc/openvpn
  ##      service openvpn start
  ##      service openvpn status
  ##      cp /usr/share/doc/openvpn/examples/sample-config-files/client.conf /etc/openvpn/easy-rsa/keys/client.ovpn
  ##      
  # Generate Certificates and Keys for Clients
  ##      ./build-key dennyzhang
  ##      
  # Combine 4 files into one
  ##      /etc/openvpn/ca.crt
  ##      /etc/openvpn/easy-rsa/keys/client.ovpn
  ##      /etc/openvpn/easy-rsa/keys/$client.crt
  ##      /etc/openvpn/easy-rsa/keys/$client.key
  #
  ## docker commit -m "initial" -a "Denny<http://dennyzhang.com>" 7572605bd8e7 denny/openvpn:v1
  
  # clean up
  rm -rf /var/cache/*
  rm -rf /tmp/* /var/tmp/*
  rm -rf /usr/share/doc && \
  apt-get clean && apt-get autoclean
  ########################################################################################
  