How to root from adb? I have a tablet called General Mobile E-Tab 4. 
I bricked it. It stays on load animation. I can reach recovery but there are 3 options:

reboot device
wipe data/factory reset
wipe cache partition


I have pushed root files to /data/local/tmp with this guide (gave permissions also)

I have also installed VirtualBox and Ubuntu. But I can't see my device in Ubuntu:



For some reason VM shows me that and never loads:


Screenshot (click image for larger variant)

I also tried Droid Explorer, Android Commander and few programs to view tablet's files. 

They saw the device but they didn't show it's files.

I also tried mv and cp commands to move root files from /data/local/tmp to /system/bin/sh but it said:

Operation not permitted


Same for mount command:



Also, when sideloading a file from abd, the device gives error: Installation aborted

So what can I do now?
download the SuperSU-UPDATE File

----commands-----



fastboot oem unlock

fastboot flash "SUPERSUFILE"

fastboot reboot