Root Moto E (1st gen) failed root.

[scary alien]

I'm still unsure what the SuperSU program does exactly. I thought it just acted as an invisible middleman for any root permission requests from apps and stepped in before the Android blocked them?

The SuperSU application get's notified when you make a request to use the "su" binary / executable. It (SuperSU) then checks it's database to see if the requesting program/app has already been granted permission or not to execute the su binary. If it hasn't been encountered before, it will then prompt you with a pop-up asking if you want to grant or deny permission for the requesting app/program to be given root access.

And TWRP installed OK but I really don't know what function this performs now. I thought it was the custom ROM and would show a different ROM when I rebooted. Do I now have to boot into the TWRP UI and point it towards a specific boot ROM on the SD Card or phone?

TWRP is a custom recovery and is not a custom ROM. A custom recovery allows you to install a custom ROM (among other things, of course). A custom ROM is just a version of Android that a dev has tweaked to have special features not present in the stock/factory ROM.

Typically, you would find a dev's ROM thread, carefully read and follow it's specific information / directions / instructions, download the ROM .zip file to your device, verify it's MD5 checksum on your device to make sure it transferred properly, launch your custom recovery, make a Nandroid backup, save that backup off of your device to somewhere safe, do the wipes that are indicated by the dev's ROM thread, flash the custom ROM, optionally flash the gapps (Google apps package) if necessary/relevant, and finally reboot and enjoy playing with your shiny new custom ROM.

 

[Andy McG]

The SuperSU application get's notified when you make a request to use the "su" binary / executable. It (SuperSU) then checks it's database to see if the requesting program/app has already been granted permission or not to execute the su binary. If it hasn't been encountered before, it will then prompt you with a pop-up asking if you want to grant or deny permission for the requesting app/program to be given root access.



TWRP is a custom recovery and is not a custom ROM. A custom recovery allows you to install a custom ROM (among other things, of course). A custom ROM is just a version of Android that a dev has tweaked to have special features not present in the stock/factory ROM.

Typically, you would find a dev's ROM thread, carefully read and follow it's specific information / directions / instructions, download the ROM .zip file to your device, verify it's MD5 checksum on your device to make sure it transferred properly, launch your custom recovery, make a Nandroid backup, save that backup off of your device to somewhere safe, do the wipes that are indicated by the dev's ROM thread, flash the custom ROM, optionally flash the gapps (Google apps package) if necessary/relevant, and finally reboot and enjoy playing with your shiny new custom ROM.

Thanks SA that blew the fog away and cleared a few things up for me. I'm going to roll up my sleeves and try and push for the 3rd and final stage, a shiny new custom ROM.
I can see I have a little bit more reading to do first.
It looks as though the TWRP Manager app does the back up and installation so I'll look into that.

 

[GWH1]

Hi All,
I, too, struggled at the point of getting my Moto E 1st gen (XT1021) to enter TWRP recovery. Everything looked fine from the adb command window, but, I suspect, on reboot in recovery mode, the stock recovery was overwriting the twrp.img recovery. After many, many, attempts, I found a dead simple solution: instead of naming the file twrp.img, I renamed it recovery.img . Success at first attempt!

Hope this helps someone,
GWH