I have the kindle 7 HD 3ed(p48wvb4) gen and I get Mount: permission denied (are you rooted), this options dose not seems to work for all kindle devices.
I have tired all options here and also modded versions of the run me it just looks at me and says ya right, hoping to get Fire OS Distro off this device and go with a nice stock rom anyone got any ideas lol
I rooted other devices using Kingo http://www.kingoapp.com/android-root.htm.
I found that my Kindle Fire HD (UK original) loses root for some reason once or twice a year so I figured when it came to re-rooting it that I'd try Kingo there too.
It worked, and really it is simple and foolproof - you connect your device, it detects the device status and type, downloads what it needs, does the job, confirms that it's done and that's it. You don't need to do anything other than bite your fingernails and watch.