[T-Mobile Samsung Galaxy S 5] runthis:
You do not need root to do this. This will wipe your device, back it up if you care. When I truly thought about it, I really didn't give a hoot about a backup. Contacts are stored on my SIM.

This is a guide to help you get from 5.1.1 on a g900t to 4.4 so you can get your root on. It is important to note that you have to downgrade and it is even more important to note that you can brick your device and you assume all responsibility for actions you take.

(If you truly like 5.1.1 and custom kernels, be sure to stop here and go to this post instead -> http://xdaforums.com/showthread.php?p=61877146 )

I wanted to root my S5 and had no idea how to do that. Well duh, you pull up youtube and look for the guy with the most trusting voice, good instructions, and more likes than dislikes and root your 5.1.1 right? Nah, that bricked my phone. Then I actually had to learn about my device, others like it and spent a good 4 hours meticulously fixing my device.

Now, installing root will trigger knox but I believe downgrading to 4.4 from 5.1.1 may not, but I cannot be 100% sure since I already triggered knox thanks to Mr Youtube bricking my phone.

Once you are on 4.4 you can root your phone using a ton of guides all over the place. For someone new to rooting a samsung device your google searches may be something like "S5 root" and eventually evolve to "S5 root g900t lollipop 5.1.1" and you will get nothing, spam or people asking the same thing with others saying "You can't do that". I didn't care about 5.1.1, I hated it in fact, so these comments saying "no you can't" kinda pissed me off.

Items you will need that I will link you to ->

Odin

Android 4.4 image

Optional: Android 5.1.1 image (in case things get scary and you want to revert)

Let's Start ::

1. Download odin from your favorite source (Sorry, there seems to be too many weird links on google for this, but here is a forum post on this website -> http://xdaforums.com/showthread.php?t=2711451 ) and I am not comfortable hosting it.

2. Download Android 4.4 image, sources for this ->

Sammobile http://www.sammobile.com/firmwares/database/SM-G900T/

Alternative: http://samsung-updates.com/device/?id=SM-G900T

These sites are so damn slow. I got the image uploading to Mega atm and will update this post with a Mega link when they finish.

Optional: Download Android 5.1.1 image (ending in FOG6) so you can revert if needed, sources for this ->

Sammobile http://www.sammobile.com/firmwares/database/SM-G900T/

Alternative: http://samsung-updates.com/device/?id=SM-G900T

These sites are so damn slow. I got the image uploading to Mega atm and will update this post with a Mega link when they finish.

3. Grab your phone and turn it off.

4. Hold in the Volume Down button, the Home button and then hold down the Power button until you see a message telling you that you are going to break your phone and void your warranty. Confirm you wish to break all the things by pressing the Volume Up button.

5. Plug in your phone to your computer and open up Odin. In Odin you will see a bunch of blank boxes and hopefully one of them on the ID:COM section is blue which indicates your device is plugged in. If you see the blue box showing connected, you can continue.

6. Click Options and make sure the only 2 boxes checked are Auto-Reboot and F. Reset Time. In the section to the right (Files [Downloaded]), check the second checkbox next to "AP". Click the text labeled "AP" and select the 4.4 android image you downloaded already. The program may sort of freeze up but just wait for a few seconds and let it clear up.

(You should read the rest of these steps entirely before continuing to follow).

7. Click the start button at the bottom and wait for it to finish. You want to catch the next reboot fast so you can enter into recovery otherwise you have a sweet softbrick boot loop. If so it is no big deal, yank out the battery because you need to clear some cache and factory reset.

8. When the reboot is coming back up, quickly hold in Volume Up, Home Button and Power Button to get into androids default recovery. Once you see blue letters at the top left "Recovery Booting" you can let go of the button combination.

[IMG="Recovery Mode"]http://forums.androidcentral.com/attachments/general-help-how/153899d1417588766t-how-save-pics-update-failed-galaxy-s3-w-vm-find-update-disk-image-img_5562.jpg[/IMG]

9. Go down to the option to "wipe cache partition" using the volume keys and use the power button to select it.

10. Go down to the selection "wipe data/factory reset" using the volume keys and use the power button to select it..

11. Check the section at the top "reboot system now" using the volume keys and use the power button to select it.

12. Give it a little bit of time (2 minutes max) to get passed the tmobile carrier screen and you should see the new device setup screen. YAY you downgraded to 4.4 and now all those wonderful guides on rooting your S5 become relevant to you at last!

If you get nervous and want to chop back to 5.1.1 follow the exact same instructions but select the 5.1.1 android image instead of the 4.4 one.

I hope this helps someone new to this that is on 5.1.1 and seeing a lack of resources on getting to root and not caring about 5.1.1 in general. I actually think you can get all the features of 5.1.1 through custom roms once you get back to 4.4.

If I am missing something, left something out or mistyped something please let me know.

Rooting the S5 is really up to you. Some people swear by it, but if I can be honest, once I had it done on my phone I was severely disappointed (and felt regret) in the lackluster apps and things you can do. The best reason to root for me was to control permissions (which is a paranoia game you start to play with your apps) and freeze system apps that came with my device. Freezing the silly ass software update that kept bugging me to update was fantastic as well as the oogle of google apps I will never ever use like Google Music and TV, My Magazine, etc.