Install 64-bit Flash plugin for 64-bit Ubuntu

Answer:

1. Remove currently installed versions of Flash

sudo apt-get purge flashplugin-nonfree flashplugin-installer gnash gnash-common mozilla-plugin-gnash swfdec-mozilla

2. Visit http://labs.adobe.com/downloads/flashplayer10_64bit.html to update the filename given under if necessary

3. Download the 64-bit Flash plugin and extract it: (for example, current version is: 10.0.42.34)

wget http://download.macromedia.com/pub/labs/flashplayer10/libflashplayer-10.0.42.34.linux-x86_64.so.tar.gz && tar xvfz libflashplayer-10.0.42.34.linux-x86_64.so.tar.gz


4. Move the file in /usr/lib/mozilla/plugins for a site-wide install (or in ~/.mozilla/plugins for a single-user install):

5. Restart Firefox.

Reference: https://help.ubuntu.com/community/AMD64/FirefoxAndPlugins