Hacking Question Attempting to compress NAND backup; only saving ~2gb on an empty NAND

TehCheez · Jan 15, 2019

So I've tried multiple compression types with 7zip and WinRAR and I'm only saving roughly 2gb on both my SX OS and Hekate NAND backups.

I purchased the Switch used (couldn't find a new exploitable one at any local stores) and it came with FW 6.0.1 installed. The second I got the Switch out of the store I did a factory reset and cleared everything, turned airplane mode on, and did a NAND backup with both SX OS and Hekate in that order. My NAND should be basically empty but I'm still not getting the same compression that most others are getting. I've followed the guides on the forums and did some research on different types of compression with no luck. Since I bought it used and content was on it previously does that screw my NAND backup or am I just missing something while compressing it?

asnka · Jan 15, 2019

winrar?

TehCheez · Jan 15, 2019

asnka said:
winrar?

Are you asking if I tried WinRAR or what WInRAR is?

As I mentioned, yes I've tried WinRAR. If you're asking what WinRAR is in some good compression software that's old enough to drink: https://www.rarlab.com/

arianadark · Jan 15, 2019

whether your nand is full or empty it occupies the same amount of space

linuxares · Jan 15, 2019

arianadark said:
whether your nand is full or empty it occupies the same amount of space

Incorrect, the data is still "zero" if it's nothing written. My brand new Switch I managed to get down to 12gb from 32gb with 7zip LMZA2 compression.

night_hawk · Jan 15, 2019

uhm i used winrar to compress my nand and it is now 330 MB or so

Godofcheese · Jan 15, 2019

Think my Nand backups are like below 2Gb or something, can't remember 100%
Then I'm just using latest winrar version with standard settings :>

shadowofdarkness · Jan 15, 2019

Your nand image is encrypted doesn't matter if it is empty and zeroed out. It will not be zeros that you are compressing.
The encryption would be bad of it was as them people world be able to tell where actual data was in the image.

ghjfdtg · Jan 15, 2019

Data is not actually deleted but marked as deleted. It remains in the partitions lowering the compression ratio. Only way is to clean it up by zeroing out and reformatting them.

Asia81 · Jan 15, 2019

night_hawk said:
uhm i used winrar to compress my nand and it is now 330 MB or so

Same, my .rar is arround 500mb

pLaYeR^^ · Jan 15, 2019

I compressed my NAND backup with WinRAR and it's now about 480 MB.

GizmoTheGreen · Jan 15, 2019

>people unironically using WinRAR after the 90's

chippy · Jan 15, 2019

shadowofdarkness said:
Your nand image is encrypted doesn't matter if it is empty and zeroed out. It will not be zeros that you are compressing.

Dont think people get this or forget that it's encrypted

gg11 · Jan 15, 2019

When you perform a console "reset", it only resets the settings to stock settings, delete some files in the filesystems inside, but like on a computer when you delete a file, the underlying "dirty" block" (eg old data) are not erased. Only a full reformat of the filesystems would really clear the old block. It's not done by the factory reset.
So when you try to compress the dump, you try to compress all the old blocks of the previous owner as well...

Maybe with hactool memloader, you could backup the files, and rebuild a clean empty filesystem ?

chippy · Jan 15, 2019

Ok everyone, your all for getting that the nand is encrypted. Meaning all data (blank or not) is random crap so people can't see what's in the data. The blank space is encrypted too so people can't see where in the drive (nand in this case) is the real data for them to focus on decrypting.
It's the luck of the draw on how small your nand will compress using the same tools and same settings.
You have the SAME chance of the nand to compress worse when you delete something (actully 0ing out the space) then putting something onto the nand because it's encrypted

wurstpistole · Jan 15, 2019

arianadark said:
whether your nand is full or empty it occupies the same amount of space

No. When nothing is installed, it should be around 2 to 2.5gb or around that ballpark.

linuxares said:
Incorrect, the data is still "zero" if it's nothing written. My brand new Switch I managed to get down to 12gb from 32gb with 7zip LMZA2 compression.

I have stuff installed and the backup is around 4gb compressed. You can get way better than 12gb.

shadowofdarkness said:
Your nand image is encrypted doesn't matter if it is empty and zeroed out. It will not be zeros that you are compressing.
The encryption would be bad of it was as them people world be able to tell where actual data was in the image.

Of course it matters, hence the huge compression that is possible

linuxares · Jan 15, 2019

wurstpistole said:
No. When nothing is installed, it should be around 2 to 2.5gb or around that ballpark.

I have stuff installed and the backup is around 4gb compressed. You can get way better than 12gb.

Of course it matters, hence the huge compression that is possible

I noticed I f-ed up. It wasn't my brand new Switch, it was my original Switch it was from... DERP!

shadowofdarkness · Jan 15, 2019

wurstpistole said:
Of course it matters, hence the huge compression that is possible

Zeros compress well, encrypted zeros do not compress the same. Since they are no longer zeros.

A nand image is encrypted data even the empty space is encrypted. You will never get that good of compression in this case. Some variation is possible on compressed size depending on the encrypted data but it will never be all zeros.

hippy dave · Jan 15, 2019

Someone posted instructions to zero out the empty portions of a nand image, to make it compress like it was new. I don't remember what thread it was in tho, and not sure what you should search for, but look around if you're particularly keen.

TehCheez · Jan 15, 2019

gg11 said:
When you perform a console "reset", it only resets the settings to stock settings, delete some files in the filesystems inside, but like on a computer when you delete a file, the underlying "dirty" block" (eg old data) are not erased. Only a full reformat of the filesystems would really clear the old block. It's not done by the factory reset.
So when you try to compress the dump, you try to compress all the old blocks of the previous owner as well...

Maybe with hactool memloader, you could backup the files, and rebuild a clean empty filesystem ?

This makes sense, I was thinking that might have something to do with it. I may look into using hactool in the future but that'll have to be when I've got a free weekend or something. Even tho both my backups are taking up roughly 60gb, I've got backups and that's what's important.

hippy dave said:
Someone posted instructions to zero out the empty portions of a nand image, to make it compress like it was new. I don't remember what thread it was in tho, and not sure what you should search for, but look around if you're particularly keen.

@gg11 mentioned what tool to use for it. I may look into it in the future.

Hacking Question Attempting to compress NAND backup; only saving ~2gb on an empty NAND

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