You can still checkout Yocto releases since the Morty branche. There is no guarantee that any of these will still build although at the time of creation they built, installed and booted. However Kirkstone is a current Yocto LTS version (see for Yocto support plans https://wiki.yoctoproject.org/wiki/Releases. For Morty the separate parts (u-boot, kernel and rootfs) must be installed manually. After Pyro this is optional, you can use flashall or Flash Tool Lite and overwrite your factory image.
In the following we assume you want to use the latest (Scarthgap) and will only mention deviations for the older versions when absolutely needed.
Going from factory to Scarthgap, when you install the btrfs image everything is erased, see the Understanding the partitioning scheme in this documentation.
Consider that the Edison allows you only to log in as root, and no root password is set. You know what can come of that. To secure the device, as a starting point you probably would like to create a user account, assign that sudo privileges, and configure sshd so that root logins are forbidden. This will still allow you to login via the console (the terminal connected via USB).
In case things go wrong, interrupt the boot by pressing
If you really mess up the device, for instance by installing a broken u-boot (I did this), or break the u-boot environment variables in such a way that nothing boots, I provide the recovery tools and an image (or you can recover your own if you like). Note that recovery here means recover the Edison so that it will boot again. All the partitions (except the factory partition) will be wiped, so if you have anything important on the device, you might want to back that up in advance. In particular, the factory partition contains the address for the Bluetooth device, and if you manage to loose that there is no way to get it back. Make a copy of the files in /factory and save them in a safe place, whatever you do next.
Nevertheless, you might find ways to break the Edison that nobody thought off. In that case, I told you so informed you thusly. You do get to keep the pieces.
With that out the way: the original Edison image has the same potential to break things, is badly secured and the image software is based on sources that are many years old (i.e. has many known security issues). At least Yocto Scarthgap is being actively maintained. And our testing kernel applied here is for now not more than 10 weeks behind the latest official Vanilla release.
© 2018 Ferry Toth