The first program is gMTP It’s intended for managing MP3 players, but it works great for managing devices like the Kindle Fire HD. To install it under Ubuntu, just use this command: To connect to your kindle, just plug the USB cable into your computer and the Kindle, start gMTP, and click “Connect.”
You’ll be able to navigate the files on your Kindle much as you would on the Desktop. You can add and remove folders and transfer files back and forth. On the Kindle side, the app you’ll want to install is the ES File Explorer. It’s a file manager for Android similar to Nautilus in Ubuntu. It’s how you’ll actually be able to access the files you’re transferring to your Kindle.
There are also a number of open source applications that you can download to your computer and then transfer to your Kindle. In either case, you’ll have to allow the use of unknown apps on your device. To do this on your Kindle Fire HD, just go into the “Settings -> Device” and turn the “Allow Installation of Applications from Unknown Sources” option to “On.” To install the app, just navigate to where you stored it, tap on it, and you’ll be asked whether you’ll wantt to install it.