Recently with Ubunt also encountered this problem, search this answer
Refer to the original link: http://forum.ubuntu.org.cn/viewtopic.php?t=387865
2, remove the "download additional data unsuccessful" annoying notification, method:
$CD/usr/share/package-data-downloads/
$sudo RM *-RF
$CD/var/lib/update-notifier/package-data-downloads/
$sudo RM *-RF
$CD/var/lib/update-notifier/user.d/
$sudo RM data-downloads-failed
And then two scenarios,
1 You can manually copy the downloaded flash to the. Mozilla/plugins directory in the home directory
2 or follow the below. But the West way but the following way I didn't experiment
$ sudo dpkg-reconfigure flashplugin-installer
[sudo] password for Leejiafang:
Enter the path of the previous download package, OK.
Installing from local file/home/leejiafang/tmp/adobe-flashplugin_11.2.202.238.orig.tar.gz
Installing from local file/home/leejiafang/tmp/adobe-flashplugin_11.2.202.238.orig.tar.gz
Flash Plugin installed.
Flash Plugin installed.
Turn: After a few days of groping, finally arrive to install Flashplugin-installer method