1.去下载×.tar.gz包，如：flash_player_npapi_linux.x86_64.tar.gz

2.解压

tar -zxvf flash_player_npapi_linux.x86_64.tar.gz

3.安装方法可以参照，解压文件中的readme.txt

Installing using the plugin tar.gz:    o Unpack the plugin tar.gz and copy the files to the appropriate location.      o Save the plugin tar.gz locally and note the location the file was saved to.    o Launch terminal and change directories to the location the file was saved to.    o Unpack the tar.gz file.  Once unpacked you will see the following:        + libflashplayer.so        + /usr    o Identify the location of the browser plugins directory, based on your Linux distribution and Firefox version    o Copy libflashplayer.so to the appropriate browser plugins directory.  At the prompt type:        + cp libflashlayer.so 
     
          o Copy the Flash Player Local Settings configurations files to the /usr directory.  At the prompt type:        + sudo cp -r usr/* /usr
     

如果看不懂可以看下面的方法：

1）找到火狐的插件文件夹

root@debian:/home/kevin/下载# find / -name mozilla/usr/share/ca-certificates/mozilla/usr/share/mozilla/usr/lib/mozilla/home/kevin/.cache/mozilla

2）可以看到文件夹/usr/lib/mozilla，插件文件夹就在里面

root@debian:/home/kevin/下载# ls /usr/lib/mozillaextensions  plugins

3）复制 libflashlayer.so 到 /usr/lib/mozilla/plugins

cp libflashlayer.so /usr/lib/mozilla/plugins

4）复制解压文件usr中所有文件到/usr

sudo cp -r usr/* /usr

至此重启浏览器可以使用flash player