Why this tutorial?
The easiest way to install Flash in Ubuntu is visiting a website that uses Flash and then following the Install missing plugins Firefox prompt. More details on that process here.
Sometimes, for some reason, that process doesn't work. If so, here's a good backup plan.
Download the Flash Player
Search for the phrase flash player download
In the search results, you should find Adobe's download center. Click on that.
The download center will offer you three download options—.tar.gz, .rpm, and YUM. You want to download the .tar.gz file.
You should be prompted by your web browser what you want to do with the compressed file. Firefox's default is to open it with the archive manager. That's a good choice. If you are not offered a choice, then download the file to your desktop and double-click the .tar.gz; the archive manager application should launch.
Prepare the download file for installation
Once the archive manager opens, click the Extract button.
You'll be asked where to extract the compressed .tar.gz file to. In this example, I chose the desktop, but just put it somewhere you can easily find later.
Install the extracted download file
Press Alt-F2. This will open up a Run Application dialogue. In the dialogue, type
This will launch the file manager (Nautilus) as root (computer administrator), allowing you to make system-wide changes.
Since you are making system-wide changes, you'll be prompted for your password. Enter it.
Navigate to the download file's location. Note that the user in this administrative file manager session is root, and so the file manager will open to the location /root. If you put the file in /home/username/Desktop, you'll have to navigate to that location. In this case, I put it in /home/cynthia/Desktop, so I had to navigate to /home/cynthia/Desktop/install_flash_player_9_linux to get to the installer file.
Once you're in the installer directory, double-click the flashplayer-installer file. You'll be asked how you want to run it. Select Run in Terminal.
You'll be prompted in the terminal to press Enter to continue. Do that.
Then you'll be asked to exit any browsers you have running. So close Firefox (or Opera, Epiphany, or whatever web browser you might be using). Then press Enter
Then you'll be asked to enter the installation path. The installation path should be
then press Enter
You'll be asked if you want to proceed with the installation. Press y then Enter
Then you'll be asked if you want to perform another installation. Press n then Enter. The terminal window should close after that.
Now you can delete the install_flash_player_9_linux folder, and Flash should now be installed for your web browser.