[Q] Changing operating systems?

M919UVUFN4B and M919UVUEMK2 are both knox enable firmwares. You can change between then but never go back to M919UVUAMDL. Putting on a different rom is changing the os on the phone.

MDL is incompatible with the boatloader, if you have installed MK2 o NB4. You can brick your phone if you downgrade to MDL.

Sent from my SGH-M919 using XDA Premium 4 mobile app

wolfen1086 said:

Thanks. Can I simply root and remove Knox? I hate that app as much as my ex wife's cat.
Right now I have 12 hours left downloading the 4.4.2 one so after installation it will be rooted and recovery will be changed to cwm
Oh and why not go back to MDL? Is there a problem with that is or is it just incompatable?

Sent from my A200 using XDA Free mobile app

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The Knox apps and the Knox flag are 2 different things. They are both security related, but the Knox flag is what gets tripped/set if you every flash a non-stock recovery to the phone.

The Knox apps are what can be used to Shut down/wipe a phone if stolen, etc

If you have ever had the MK2 or NB4 bootloader on the phone, you now have the Knox flag. You can not go back to a bootloader that doesn't have the Knox flag. MDL bootloader doesn't have the flag, so you can't flash it once you've had MK2 or NB4.

Rob

---------- Post added at 04:28 PM ---------- Previous post was at 04:23 PM ----------

wolfen1086 said:

Ok yall I have a brick It was a Tmobile SGH-M919 and the rirmware was M919UVUFNB4. Question, since it only boots into download mode, not even recovery, can I change between M919UVUFN4B and M919UVUEMK2 and M919UVUAMDL?
Just wondering cause I'm trying to learn how to change an operateing system on phones
I've gotten pretty good at rooting and roms now its time to learn something new

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Just FYI, the phone has multiple bits of software. The bootloader and the recovery are in their own partitions. The firmware is like device drivers under Windows, and there is the radio(s). And then there is the OS. It's made up of the kernel and the interface/apps.

When you download the stock ROM from Sammobile, you are getting a partition table, a radio, a recovery (stock), the firmware and the OS. Which is why everyone on several threads has suggested you to download and install that with ODIN. It should get you back to a working phone.

Rob

wolfen1086 said:

Mine trips the counter that says I have changed to a custom rom, so that means I have the knox flag right? Cause when I rooted I uninstalled and deleted the knox app, tried that once before I was rooted and wound up doing a hard reset because of that app

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No, the Custom ROM flag is different than the Knox flag.

If you boot into the Bootloader, if you have a Knox bootloader, it will say the words Knox and then have a 0x0, or 0x1, next to the word Knox.
No Knox shown, you have a bootloader that doesn't have Knox.

If 0x0 shown, the the Knox counter is NOT tripped. If 0x1 is shown, then you have a Knox bootloader and the Knox flag has been tripped.

Rob

mguzman0971 said:

MDL is incompatible with the boatloader, if you have installed MK2 o NB4. You can brick your phone if you downgrade to MDL.

Sent from my SGH-M919 using XDA Premium 4 mobile app

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THIS IS INCORRECT! I keep seeing this all the time. THIS IS WRONG. It will NOT brick your device if you try to flash MDL firmware to a NB4 firmware. Odin will simply say "fail" and nothing will get written.

About your issue OP, you need to flash the NB4 tar file in Odin to recover from your soft brick. Then you can flash a recovery or what have you to get back to however you wish. You cannot go back to the MDL firmware after taking the MK2 or higher firmwares. The bootloader will block any attempts(as stated above).