How to install Cyanogenmod 13 on LG G2 (d802)

I’ve been a fan of Cyanogenmod since 2012 when I installed it on my HTC Hero. The Hero went and the LG G2 came, which I used for some time with the stock ROM, but I knew the time for Cyanogenmod would come. After using CM12 for some time I wanted to try installing CM13 again. My original problem was that I would be stuck in a bootloop when using CM13. After a while I found that this was caused by using the wrong bootloader, and I installed a “hybrid” bootstack from this source:

http://forum.xda-developers.com/lg-g2/development/boot-g2-hybrid-bootstacks-t3183219

After that I rebooted into recovery and flashed the bootstack, CM13, and the Google apps all in a row. CM13 was working, yay! Unfortunately my recovery wasn’t working anymore. It seems that with this bootstack, you need a “bumped” recovery. I just assumed that the default recovery would be bumped, but I was mistaken.

Before I proceeded to get a working recovery again, I decided to do a backup of my otherwise working and already set up system following  this guide:

http://forum.xda-developers.com/showthread.php?t=1818321

In the guide it mentions that you need Busybox, but you don’t need it if you run Cyanogenmod 12. I run the backup then with the following commands:

Shell 1:

adb forward tcp:5555 tcp:5555
adb shell
su
nc -l -p 5555 dd if=/dev/block/mmcblk0

Note that I ommited the “-e” option since it gave me an error.

Shell 2:

adb forward tcp:5555 tcp:5555
cd /path/to/store/the/backup
nc 127.0.0.1 5555 | pv -i 0.5 > mmcblk0.raw

This backup worked quite nice (as it seems), but it took the whole night to complete. Plus, I have no idea how this should be recovered. I’ll have to check that thread in that case.

Now, back to my original problem. I couldn’t boot into recovery due to the following error message:

ERROR: boot certification verify
 [690] ---------------------------------------
 [740] 
 [...] Secure booting Error!
 [...] Cause: boot certification verify
 [...]
 [...] ---------------------------------------

I tried flashing a new TWRP recovery (3.0.2-1 from blastagator) as provided in this thread:

http://forum.xda-developers.com/lg-g2/development/twrp-twrp-2-8-0-0-kernel-f2fs-tools-t2898705

Since my recovery was broken, I couldn’t use that one to flash it. I tried flashify, but it didn’t work. Then I installed the Cyanogenmod recovery (which worked), but I couldn’t flash blastagator’s recovery from there either due to a failure in signature verification.

Well, that’s the end for now I guess: I have a working basic recovery (without backup options), so for now I’m happy with a working Cyanogenmod 13 and just did a first backup with Online Nandroid .