ubuntu 安装 firefox 的 jre plugin

https://www.java.com/en/download/help/enable_browser_ubuntu.xml

Mozilla Firefox

• Become the root user by running the su command and then enter the super-user password. Type: 
  sudo -s
• Create a directory called plugins if you do not have it. Type: 
  mkdir -p /usr/lib/firefox-addons/plugins
• Go to Mozilla plugins directory before you make the symbolic link. Type: 
  cd /usr/lib/firefox-addons/plugins
• Create a symbolic link. Type: 
  ln -s /usr/local/java/jre1.7.0/lib/amd64/libnpjp2.so
• Restart your browser and test Java