Some time ago, we wrote about how the folks over at GTVHacker managed to root the Google Chromecast. Shortly thereafter, the secure boot vulnerability was closed, and this root method no longer worked. For this reason, many users refuse to let new Chromecast units connect to the Internet before first rooting and disabling OTAs.
Naturally, if you have already connected your Chromecast and it has already updated its firmware, you cannot root the device at the moment. However, for those lucky enough to have a unit running the original shipping firmware, you now have a streamlined method of acquiring root thanks to XDA Forum Member tchebb and his USB image flashCast.
So what is flashCast, exactly? Well, as described by the developer:
FlashCast is a USB image that provides a standardized way to mod your Chromecast. Think of it like a recovery which runs off of a USB drive. No more struggling with the limitations of the GTVHacker image, which is hard to modify and can only flash the /system partition. FlashCast is based on shell scripts, so it you can use it to do anything you can do with a root shell. It also comes with a comprehensive suite of helper functions, so many tasks actually become much easier than they would be using a regular shell.
In other words, it’s an easy and standardized image that works analogously to a recovery. So what do you need to use this? As stated above, you first need a Chromecast with a vulnerable bootloader. In addition, you need the latest version of flashCast, a USB drive of at least 128 MB, and a powered micro USB OTG cable.
Once you have the required components, simply install flashCast to the USB drive with a low-level write using dd on Linux or Win32DiskImager on Windows. From there, use the special instructions to connect the device to the storage, keeping in mind the proper order.
To get started, head over to the original thread. Once again, this will only work with the original shipping firmware and will not work if your device has been updated. However, if you have a brand new, unused Chromecast, it’s practically begging to be flashCasted.