[ZenFone 2 General] fg:
Tl;dr - 1) download zip from asus 2) download tethered recovery 3) copy the zip to the sd card 4) run tethered recovery utility 5) install via twrp/cwm menus

I am creating this thread to document my experience with a failed update and being stuck in a brick state with the seemingly random but present permission denied error when trying to fastboot flash. Most of this is not new, but rather a collection of existing resources with a focus on a specific, uncommon issue(s)

Tomorrow I will edit this message with links to the threads and posts which got me going again today. This is currently a workaround to restore the system, the bootloader is still falling.

Recommended reading:

-ansebivi's wonderful ota flash guide - links all the major files, lays out all the theory

-the official tethered recovery thread, my missing link

-thebugruss's permission denied thread, alludes to the magic system recovery properties of tethered recovery and had some great information

- all the other xda and Google hits that reference these errors

I had been putting off the .137 ota update for a while and finally decided to let in download and install. My z551 was not rooted and had a locked boot loader. the update failed and re booted back into .97 without issues for a few minutes before turning off. When I rebooted, I was stuck in the wonderful boot loop. Reading through the boot loop recovery section of the ota thread, I start top down and found my fastboot would not properly install anything. Error permission denied. Then I tried the adb sideload which failed with a cannot read error on the pc. Finally I went to try the install via zip in the external storage, but recovery would not start. Instead the ZenFone either fell back to fast boot our started at the powered by Android screen. Many posts referenced wiping the cache via fast boot, ask permission denied fire me. Having seen some success discussion with vampirefo tethered recovery, I was able to at least get back to recovery and poke around adb shell. Adb shell here had no root privileges and could not even read /sdcard, but at least usage-wise my /data looked whole, /system was empty and /recovery did not look right. Adb sideload failed in this recovery, wiping the caches here did nothing, the install from zip menu options did not work. Encouraged by the process, I found the latest stock tethered recovery utility updated back in July and trying twrp instead of cwm I was finally able to get install from zip working. Side load did not work under twrp, but gave a different error than stock and cwm

I never wiped /data and had a found all my settings and and data intact. Fastboot still gives permission denieddenied errors, but that will have to be fixed another day.

From all my reading, there doesn't seem to be a common reason for permission debuted in fast boot (threads exist of rooted, un rooted, never rooted, locked and unlocked bootloader). At least one post indicated a result of the ww fastboot on a cn or tw device. For most, permission denied still allows for some writing. My current guess is that each subsequent attempt and failure corrupted system and recovery

Next steps:

Perform a property nand backup in twrp

Check if my fast boot matches my phone sku

Fix fastboot (preferably without unlocking the bootloader, but definitely i will need to root to investigate

-f