[General Topics] blackhawk:
How long is a huge ball of string?

No simple answer...

This is for those who are new to Android development and basically have NO understanding about the partition structure. I will give a high-level introductory explanation. PC GNU/Linux users: please note this is completely different from x86 (PC Linux) partition table. You will not come across partitions denoted as sda1, sda2, sdb1, sdb2, and so on. Instead, it will be structured as follows:

/boot

This is the partition that has all the data that is necessary for the phone to boot. It includes the kernel and the RAMDISK (these are the only components of the operating system that are stored in this partition. The remaining are stored in /System). Without this partition, the device will simply not be able to boot. Wiping this partition from recovery should only be done if absolutely required and once done, the device must NOT be rebooted before installing a new one, which can be done by installing a ROM that includes a /boot partition.

/system

This partition basically contains the entire operating system, except the kernel and the RAMDISK (as mentioned in /boot explanation). This includes the Android User Interface as well as all the system applications that come pre-installed on the device. Wiping this partition will remove Android from the device without rendering it unbootable, but you will still be able to boot into the /recovery partition to install a new ROM.

/recovery

The recovery partition can be considered as an alternative boot partition that lets you boot the device into a recovery console for performing advanced recovery and maintenance operations on it. Think of this like a proprietary recovery partition that PC companies put on prebuilt PCs. When you flash a custom recovery such as TWRP or CWM, you are overwriting this partition.

/data

Also called userdata, the data partition contains the user’s data – this is where your contacts, messages, settings and apps that you have installed go. Wiping this partition essentially performs a factory reset on your device, restoring it to the way it was when you first booted it, or the way it was after the last official or custom ROM installation. When you perform a wipe data/factory reset from recovery, it is this partition that you are wiping.

/cache

This is the partition where Android stores frequently accessed data and app components. Wiping the cache doesn’t effect your personal data but simply gets rid of the existing data there, which gets automatically rebuilt as you continue using the device.

/misc

This partition contains miscellaneous system settings in form of on/off switches. These settings may include CID (Carrier or Region ID), USB configuration and certain hardware settings etc. This is an important partition and if it is corrupt or missing, several of the device’s features will will not function normally.

/sdcard

This is not a partition on the internal memory of the device but rather the SD card. In terms of usage, this is your storage space to store your media, documents, downloads, pictures, videos, ROMs etc. on it. It is like the equivalent of the ' Users/[Username] ' folder in Windows and ' /home/~ ' folder in x86 Linux. Wiping it is perfectly safe as long as you backup all the data you require from it, to your computer first. Though several user-installed apps save their data and settings on the SD card and wiping this partition will make you lose all that data.

On devices with both an internal and an external SD card – devices like the Samsung Galaxy S and several tablets – the /sdcard partition is always used to refer to the internal SD card. For the external SD card – if present – an alternative partition is used, which differs from device to device. In case of Samsung Galaxy S series devices, it is /sdcard/sd while in many other devices, it is /sdcard2. Unlike /sdcard, no system or app data whatsoever is stored automatically on this external SD card and everything present on it has been added there by the user. You can safely wipe it after backing up any data from it that you need to save.

/sd-ext

This is not a standard Android partition, but has become popular in the custom ROM scene. It is basically an additional partition on your SD card that acts as the /data partition when used with certain ROMs that have special features called APP2SD+ or data2ext enabled. It is especially useful on devices with little internal memory allotted to the /data partition. Thus, users who want to install more programs than the internal memory allows can make this partition and use it with a custom ROM that supports this feature, to get additional storage for installing their apps. Wiping this partition is essentially the same as wiping the /data partition – you lose your contacts, SMS, market apps and settings.

/Boot (Is NOT viewable in Android)

/Recovery (Is NOT viewable in Android)

/Data (Userdata) (Is viewable in Android)

/Cache (Is viewable in Android)

/System (Is viewable in Android)

/Misc (Is NOT viewable in Android)

Ram

https://developer.android.com/topic/performance/memory-management

Understanding Firmware naming:

N986USQU1ATGM

N=Note

986U or F etc, the model of device

SQ, FX etc = CPU and model specific

U,S,E = Update, Security, Engineering, respectively

1,2,3,4,5 etc = bootloader revision (This is important! You cannot go to a previous revision)

A,B,C,D = Android version

T, U = Year (T=2020, U=2021 etc)

A,B,C etc = month (January A - December L)

1 - 9 and then A - Z =build compilation. This basically means how many builds there are in a month. They start at 1 and go to Z

So N986USQU1ATGM would be

N968-U-SQ-U-1-A-T-G-M

N968U (Note 20 Ultra Carrier version), SQ (Snapdragon), U (Update), 1 (Bootloader version), A (Build 10), T (2020), G (July), M (22nd build)

How to enter Download Mode:

Turn off the device.

Connect USB cable to your PC (Leave it disconnected from the phone)

Press and hold down the Volume Up and Volume Down buttons. While they are still pressed, plug in the USB cable into your phone.

The phone will go into download mode press volume up. In Odin you will see that phone is added.

Dirty Flash:

I would only do this if you are having to manually update to the newer firmware and would not do it if you are coming/going to U/U1 or from beta firmware or if you are on an old firmware. I'd also highly recommend doing a back up prior to the doing this

Load these into Odin

BL

AP

CP

HOME_CSC

Do NOT flash CSC or USERDATA, either of these WILL wipe your device

This is a "dirty flash" and these can sometimes cause issues. Keep in mind if things start going sideways and stuff starts not working right, your first step to a solution will be to wipe the device.

Tips on flashing U1 Firmware:

You will have to wipe, can NOT dirty Flash going between U and U1 firmware

Use the patched ODIN linked in post #2 or #3, Odin3_v3.13.3b (They are exactly the same)

Have an active US Carrier SIM installed to get carrier features

If you get your CSC Stuck on XAA/XAA/(Insert your carrier here), and can not get Carrier options back.

PIT files

https://ihax.io/samsung-pit-files-explained