从Adobe官网下载flash：http://get.adobe.com/cn/flashplayer/
我下载的版本是：flash_player_npapi_linux.x86_64.tar.gz
找到正确目录
sunone@HY-Chess:~$ whereis firefox
firefox: /usr/bin/firefox
sunone@HY-Chess:~$ find /usr/ -name firefox
/usr/bin/firefox
find: `/usr/lost+found': Permission denied
sunone@HY-Chess:~$ find /usr/ -name mozilla
/usr/share/mozilla
/usr/share/ca-certificates/mozilla
find: `/usr/lost+found': Permission denied
/usr/lib/mozilla
查看plugins 到底放在哪里
sunone@HY-Chess:~$ ls /usr/share/mozilla/
extensions
sunone@HY-Chess:~$ ls /usr/lib/mozilla/
extensions plugins
Ok，找到插件目录 /usr/lib/mozilla/plugins
解压下载的插件安装包
sunone@HY-Chess:~/Downloads$ tar -zxvf flash_player_npapi_linux.x86_64.tar.gz
找到libflashplayer.so文件和usr/这个文件夹，复制libflashplayer.so到/usr/lib/mozilla/plugins
sunone@HY-Chess:~/Downloads$ sudo cp libflashplayer.so /usr/lib/mozilla/plugins/
把usr/文件夹复制到/usr
sunone@HY-Chess:~/Downloads$ sudo cp -r usr/* /usr
重启浏览器，插件加载成功。