[Google Chromecast] tchebb:
What is it?

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.

How do I use it?

If you prefer to follow a video tutorial, [MENTION=2212097]ddggttff3[/MENTION] has made one here. Otherwise, read on for written instructions.

Preparation

Before you begin, you'll need some materials:

A Chromecast with a vulnerable bootloader. (For the bootloader to be vulnerable, the Chromecast must have never been connected to the internet and have a rootable serial number.)

The latest version of FlashCast (the download link is at the bottom of this post).

A USB drive (minimum size 256MB) which you are willing to have erased.

A powered Micro-USB OTG cable such as this one. (Alternatively, an unpowered USB hub and unpowered OTG cable can be used as shown here. I have not tested this method and cannot help you if your USB drive is not detected.)

Installation

Once you've gathered everything required, you can install FlashCast to your USB drive. To do so, you need to write the .bin file contained in the FlashCast .zip file you've downloaded to your drive. Simply using a file explorer to drag the .bin file to your USB drive is not correct and will not work. The specifics of doing a low-level write differ depending on OS, but, in general, Linux and OS X users should use dd and Windows users should use Win32DiskImager. This operation will erase your flash drive.

After you've written the .bin file to your USB drive, your computer will no longer recognize a filesystem on it. This is normal. In order for FlashCast to set up the drive's filesystem, you need to boot your Chromecast from the drive. To do this, perform the following steps:

Connect the male end of your Micro-USB OTG cable to your Chromecast.

Plug your USB drive into the USB-A female connector of the OTG cable.

Simultaneously hold the button on your Chromecast and connect the Micro-USB power connector to the female Micro-USB port of the OTG cable.

The power must be connected last. If it is not, your Chromecast may fail to detect the USB drive and boot up normally. If this happens, simply repeat the process, making sure to perform the steps in the correct order.

If FlashCast was copied correctly, you will see a red light on your Chromecast for approximately 9 seconds. It will then turn white and your TV will display a screen containing the FlashCast logo (shown at the top of this post) and various instructions. Once you see this screen, you may release the button. The screen will appear for another 9 seconds or so, after which your Chromecast will reboot on its own to the stock image. After it has rebooted (you may disconnect the power when it starts to boot into the stock image if you're worried about it updating), FlashCast is installed on your USB drive and ready for use. Your device is NOT rooted at this point and can still be updated by Google. To root, you need to flash a mod such as Team Eureka's Eureka-ROM. When you plug the drive into your computer, it should appear as an empty drive which you can copy files to.

Usage

FlashCast-compatible mods are distributed as .zip files. To flash a mod, simply copy it to the USB drive with the name eureka_image.zip. Do NOT use dd as you did in the previous section. If you do, you will have to repeat the whole process. Instead, just copy it onto the drive's filesystem as you would any other file. FlashCast is also capable of flashing a GTVHacker-style raw system image; if there are no native FlashCast mods present and the system image is in a file called Chromecast-Rooted-System-GTVHacker-cj_000-July27-635PM.bin, it will be flashed. This method of flashing is very inflexible and is not recommended.

How do I develop for it?

If you are interested in creating mods for FlashCast, please see the developer thread.

Who made it?

FlashCast is based on a generic Buildroot Linux image. Its mod framework was written entirely by me, but I couldn't have done it without the help of various individuals. Thanks, [MENTION=5376781]cj_000[/MENTION], for helping me and putting up with my stupid questions in IRC. And thank you, [MENTION=3038499]tvall[/MENTION], for releasing your update-free images so promptly up until now. Without those, FlashCast would have a much smaller potential user base.

Where do I get it?

Downloads and source code are available at FlashCast's GitHub repository. The latest version is currently v1.3.