What I want to do
I am using Kubuntu 14.4 and like to use
kvpm for my LVM-needs. I have a partition and a Logical Volume. On both is data. I would like to encrypt each of those. https://wiki.ubuntuusers.de/System_verschl%C3%BCsseln/ gave me a first idea, but is not quite what I was thinking about:
Is it possible to do that without having the data deleted (and thus not having to play the data back from a backup)? How do I do this for a partition and how do I do this for a Logical Volume?
Wiping empty space
I read that I would have to write pseudo random numbers on the entire partition before encrypting in order to have solid encryption (which would delete my data of course). Why should I do this if I encrypt everything anyways? Is it because only the saved files are encrypted and the not-used blocks are not encrypted and thus someone could read the previously delete files there? If so, can't I just write random numbers on those parts of the partition that are not used by data with
sfill as mentioned in https://superuser.com/questions/19326/how-to-wipe-free-disk-space-in-linux? However, according to https://superuser.com/a/150757/569223 this might not be enough afterall....
I read that LUKS is the way to go (http://www.cyberciti.biz/hardware/howto-linux-hard-disk-encryption-with-luks-cryptsetup-command/) - is this best practice or are there other options that are more preferable?
PS: Is the question right here or would it be better placed at http://security.stackexchange.com?