What We Have To Backup (Nandroid Backup) In TWRP Recovery

TWRP is popular custom recovery for Android.It gives more features to modify and customize our Android OS.The one of the most popular feature of TWRP recovery is a Nandroid backup. 

Nandroid backup is a kind of snapshot or mirror copy of your current state of android OS. And you can restore it at anytime When you want to get back to that state of your Android OS again. 

But might be you are confuse which partitions you have to backup while using TWRP backup feature. first of all, we need to understand these partitions,  which we see in TWRP recovery to backup.

System: This is the main partition which contains all Android OS system files.

Boot : This partition contains the files which helps Android OS to boot into.

Vendor: As the name suggest ,this partition contains the files which provide by the manufacturer (OEM's) in the android OS to customize as the need.

Data/User Data: This portion contains the all user data including apps user installed.

Cache: This partition contains only the cache data , which is temporary stored in Android.

Recovery: This partition contains the files of current recovery image that you are using to boot into recovery mode.

EFS : This partition holds the information of your IMEI numbers.

Vendor Image: This partition contains the device specific hardware drivers for Android device.

Logo : This partition contains the files of boot logo

Now we will discuss which partitions we have to backup while doing Nandroid Backup using TWRP recovery.

1: So if you are already using a custom ROM then you only have to backup data, boot, system, vendor partitions. Generally It works perfectly. (Less Secure)

2: But instead of option 1 above, you can backup system image, vendor image, data & boot partitions . This is recommended for mainly when you are going to backup of your stock ROM. But You can do it for any custom ROM also.  (Much Secure)

[This is because ,the manufacturers of Android devices enabled dm-verity security check on Android 6.0 & higher versions].

3: Most of the times other partitions do not need to make backup normally, in some critical cases (e.g loss IMEI numbers) you have to create a separate backup of these partitions. And only restore them when you really need them.