For detailed understanding, use a search engine. I will cover only the basics, in general, here. Will be happy to answer questions and clarify doubts.
ANDROID PARTITIONS
The following partitions are broadly found on all devices, with minor variations for each OEM (Original Equipment Manufacturer):
Boot Partition – the partition that stores the device kernel, ramdisk, firmware (modem), EFS (this contains your device IMEI, WiFi Mac address, Bluetooth Mac address, Network information, etc.).
Recovery – the partition that allows you to flash custom ROMs, kernels, etc.
System – the partition where the OS (ROM) and system apps are installed.
Data – the partition where all user apps are installed and their data stored.
Cache – the partition that holds temporary app data.
Internal Storage – the partition that saves user files like documents, pictures, videos, music, downloads, etc.
The free space that you see in any device just out of the box is your internal storage. The difference (stated capacity minus free space) is occupied by the other partitions listed above.
What is a kernel?
A kernel is an intermediary that tells the device/ OS what to do for a specific user action.
For example:
- if you press the volume up key, the kernel tells the OS to increase the volume.
- If you press the power button, the kernel decides what to do for each key combination:
- boot to system if you press the power button only
- boot to recovery if you press and hold power + volume down button (this can be different for different devices; so find the combo that works for your device)
- boot to Download mode if you press power + volume up button (this can be different for different devices; so find the combo that works for your device)
Similarly, every touch-based action that we do on the screen gets an appropriate response from the OS/ device because the kernel tells the OS/ device what to do.
In simple terms, you are directly interacting with the kernel, and the kernel in turn conveys user action to the OS/ device. The kernel controls the hardware. The user as well as all applications communicate directly with the Kernel, which in turn passes on the instructions to the OS/ hardware.
You –> Kernel –> System or Recovery or Download mode
What is bootloader?
The boot partition where the Kernel, Modem, etc. resides.
Why is bootloader locked?
Bootloader is locked to protect your data. If someone tries to bypass built-in security and tries installing something before booting to the system, the very 1st step is to unlock the bootloader. And when bootloader is unlocked, all data is wiped, and this secures your data from being accessed by someone without authorization.
Unlocking the bootloader opens the door to other partitions like recovery, which in turn is what we need to flash ROMs, Frameworks, Mods, etc.
Once you unlock the bootloader, keep it unlocked. It is easier to fix problems on a device with an unlocked bootloader. Lock the bootloader ONLY if you want to go back to 100% stock (stock ROM, stock Kernel, stock Recovery, stock EVERYTHING!), and locking should be the very LAST STEP to return to stock.
Except for warranty claim, or reselling the device, there are hardly any benefits of re-locking the bootloader.
Why install a custom recovery?
1. To take a Nandroid backup. In other words, a complete system image.
2. To installnon-stock software like Custom ROMs, X-posed Framework, etc. With custom ROMs, you can have access to latest Android versions not supported by phone manufacturer.
3. To root your device (unlocking the bootloader or installing a custom recovery or a custom ROM does NOT root your device. It only prepares your system to be rooted).
Best Custom Recovery (as of 2022) –
The very first thing to do after installing a custom recovery is to take aNandroid Backup (explained in the end) and keep it safe. This will be extremely handy later if something goes wrong.
What is rooting?
Rooting is gaining administrative access to your device. This involves breaking the security “wall” that is built into the OS for your own security.
Steps to root:
1. Unlock the bootloader
2. Install a custom recovery (to install custom ROMs, mods, etc.)
3. Root (your device is NOT rooted at steps 1 or 2)
Advantages and Disadvantages of Rooting
ADVANTAGES
1.AdAway - block ads by modifyinghosts file and not routing traffic via a VPN
2.Firewall - control app access to internet without creating a VPN connection
3. Usededicated VPN service while keeping ads away and firewall working
4.Titanium Backup or similar
• backup & restore apps and data completely• freeze apps from running in the background• disable system apps & bloatware• prevent an app from being updated (example, YouTube AdAway)
5.Viper - amazing sound (be careful, can damage hardware)
6.Schedule automatic restart of device (for devices that do not provide this feature natively)
7.Vanced YouTube - enable premium features of YouTube (this project is now off the shelf due to a C&D letter from Google)
8. Greenify can hibernate apps automatically
9. Others root apps/ mods.
DISADVANTAGES
1. Potential Security vulnerabilities
2. Some apps (like banking apps and some games) may not work
3. Loss of manufacturer warranty
4. Potential to "brick" the device
What is a Nandroid Backup?
It is a complete backup (image) of various partitions in your device. It is a good idea to check (select) the following partitions in a Nandroid backup:
System - obviously
Data
EFS – most important
Boot – most important
Recovery
Not required or safe to exclude from a Nandroid backup:
- System Image (often the largest partition)
- Cache
Always a good practice to take a Nandroid Backup before flashing anything.
A Nandroid backup does NOT backup user files like documents, pictures, videos, music, downloads, etc. You must back them up separately.
What is Bricking?
Bricking is when your device fails to boot (and is as good as a brick). There are 3 types of bricking:
Soft brick - Device starts but is stuck at boot animation. This is caused by flashing an incompatible file. Easy to fix.
Hard brick - Device provides just a haptic feedback, and nothing else. It can be fixed using "unbrick" tools and methods.
Permanent brick - Congratulations! Your device is now a brick. You can't fix it.
SHOULD YOU ROOT IN 2022 or later?
Most OEMs are offering 2 to 4 years of Andorid updates, and 3 to 5 years of security updates for most of their phones. Many of the features that were only available in rooted devices earlier, are now available in non-rooted devices too, although with slightly limited functionality, e.g. adblock, firewall, etc. So the need to root has declined drastically.
Personally, I wouldn't recommned custom ROMs either because there is no guarantee of security and privacy, open source or not. No one knows what the developer has baked into the codes. That is a risk to keep in mind.
Once you unlock Bootloader on a Samsung device, it will trip the Knox counter PERMANENTLY. There is no going back. This won't make any difference to your use of the phone, but just that it will void your warranty and there is no way you can undo the change. Besides, an unlocked bootloader comes with a lot of disadvantages in the context of some apps not working.
Also, with declining/ limited support from Magisk (whose owner goes by the name topjohnwu and is now an employee of Google), and the lack of capable alternatives, there is really not much incentive in going ahead with all the hassles of unlocking the bootloader and/ or rooting.
WARNING
Do remember that Kernels, ROMs, Custom Recoveries, etc. are all device specific. They are specific down to the component level. For example, devices like Samsung flagships that ship with Qualcomm processor in some markets and Exynos processor in other markets will require different custom ROMs, Recoveries, etc. Using the right files for flashing is extremely important to avoid bricking your device.
_______________________________________________
ADDITIONAL READINGS
1. No more lags, freezes, battery drain, heating, etc.https://r2.community.samsung.com/t5/Tech-Talk/No-more-lags-freezes-battery-drain-heating/td-p/111135...
3. Choosing the right charger https://r2.community.samsung.com/t5/Tech-Talk/Choosing-the-right-charger/td-p/11110950
4. Best Android Apps (2022)
5. How to block ads systemwide
6. Blank Thumbnails problem
7. How to turn off pop-up notifications
