For those of you having trouble getting full root using CWM or TWRP root method on the GT-i9505, this is most likely caused by SetUID in the kernel.
To fix this issue, you can install any custom kernel after installing CWM or TWRP.
I do recommend installing Adam kernel by XDA user Wanam, as it’s stock-like yet should gives you better performance/battery life over stock.
Download Adam Kernel for GT-i9505 (You can install this using CWM or TWRP recovery)
Credits – Wanam <--- Please donate to the developer or hit "Thanks" on XDA!
What is a Custom ROM?
A custom ROM is a custom, modified operating system that you can install on your Android device. Basically it's like installing Windows OS on a Macbook. By installing a custom ROM, you can bypass stock factory settings like locked hotspot tether, install new Android versions early, or even convert your phone into another OS.
With a custom ROM, you can really maximize the capabilities of your smartphone by adding custom features that have been developed by open source developers.
How to Install Custom ROMs
First, you will need to root your device, if it is not rooted yet, follow our root tutorial and root your phone.
Once rooted, you should have TWRP installed on your phone. Installation of a custom ROM is easy if you learn the basic of it. If you don't know how to install custom ROMs using TWRP recovery, see our tutorial on How to Install Custom ROM using TWRP!