Truecrypt encrypted virtual machine and compacting VDI

[stephen_liu]

When I encrypt a Windows XP 32-bit virtual machine with Truecrypt 7.0a, it takes up the full space that was alloted to the VDI (I'm using a dynamic VDI) even though I'm really using less than half. Compacting it doesn't recover any space.

I have a similar dmcrypted Ubuntu machine that I've allocated 500GB for in a dynamic VDI. It is only using 12GB or so after the initial install.

Any idea why the Truecrypt encrypted Windows XP machine shows all the space that is allocated to the VDI as used?

[vbox4me2]

This is normal behaviour as the outside(vbox) can't 'see' whats used inside(vm) anymore, even partition tables are invisible.

[wacher]

The encrypted "488GB nothing" is not "488GB nothing" anymore, but 488GB data to store.

[mpack]

Compacting it doesn't recover any space.

With what tool?, and give complete procedure please.

[sej7278]

wacher has it right - truecrypt fills its container with random junk for deniability, so your empty vdi is not empty but full, and as its random and not just zeroes it will not shrink.

dmcrypt/luks etc. on linux just encrypt the data as it comes in, there's no deniability, which is why its recommended to fill your partition with /dev/random first, otherwise you've just got empty blocks (which can be shrunk).