22MB backup on new nexus 5 - too small? Trying for the first time to root my device, using a Nexus 5 that I just got yesterday.

I'm naturally trying to back things up before doing anything that can wipe memory, but the size of the .ab files that backup programs (Nexus Root Toolkit, Holo Backup etc.) produce without root access are around the ~22MB area.

I've googled around and the consensus seems to be that it's far too small - BUT, I've only just got the device, and thrown a handful of apps (Twitter, 8SMS, etc.) onto it, no music or anything. Has this backup been performed correctly?

Also - when unlocking the bootloader and rooting the device, do I need to put the stock ROM back onto it, or does it remain there naturally?

Apologies if that last part was a bit oblivious but the places I've looked haven't been exactly clear, seeing as most of them go for custom ROMs.

Thank you in advance!
ADB backup archives are a "all or nothing" solution when it comes to restore – which is what the "unsafe warning" is about. Considering your circumstances, here are a few points to consider:


do one "full backup" excluding your system apps cannot hurt, so you could restore that as-is. Note, hoever, that this most likely also excludes data of system apps, which might include APNs, contacts, calendars, etc.
use e.g. Helium Backup (no root required) to create ADB compatible backups of all your apps separately, so you can restore them separately. This can of course also be done on the command line (specifying the package names), but this app makes it much more comfortable.
Create a full ADB backup nevertheless, including everything (except -shared, as data from your (internal) SDCard can be copied on file-level using any file manager). Though you probably might not wish to directly restore it, you might still have use for it


Considering you're after rooting in the first place, here's the background for my recommendations:


If you succeed rooting your device, and have no side effects, all the above backups just gave you a "good feeling", and you have no current need for them. But hey, it didn't hurt; could well be one of the following things happened:
If you succeeded rooting, but had to factory-reset the device due to some side-effects, you could either use Helium (or adb restore) to restore selected apps from their separate archives, or use adb restore to restore all of your user-space-apps in one run. But you could also use Titanium Backup to extract selected apps/data from the complete backup, and also restore some system data that way.
If rooting failed, and you have to factory-reset your device, you at least can restore your user-space-apps and their data from that archive, or chose to only restore selected apps as described above.


As for the size of 22 MB: That could be fine, or could be too small – depending on what apps you've installed, and how much data they have; there are no absolutes for "user-apps-only" backups (except of course for 0 byte files when you have at least 1 app installed).