It has no interest on RAM disk once power has been cut - as far as I know. On an encrypted hard disk it is useful in case the encryption is broken. On "non-spinning-rust", it is very much useful. I suppose you are aware that deleting a file just means removing its directory entry (more or less), and this is why photorec, for example, can extract about 100% of deleted pictures on an USB stick or memory card ?
Matthew suggest to dump the luks header on "an USB stick or something", which makes absolute sense when you're working on your boot disk's encryption, so the safe thing is to wipe that file off the USB stick after.
Re: "Delete this backup"
Matthew suggest to dump the luks header on "an USB stick or something", which makes absolute sense when you're working on your boot disk's encryption, so the safe thing is to wipe that file off the USB stick after.
HTH,
Colin