I recently read this nice Howto tutorial about doing backups with whole disk encryption using LUKS. Surprisingly for me this tutorial contains as the first part of step #3 a command to overwrite the new disk partition with encrypted binary zeros:
dd if=/dev/zero of=/dev/mapper/your_encrypted_disk_partition
Obviously this command will be very time consuming considering the huge disks available today. So the temptation to skip this command. If the disk is going to be filled and will be overwritten mostly anyway, because a full system backup is going to follow immediately as the next step after creating and mounting the encrypted disk device then the need to do this is difficult to understand.
What are the security risks of leaving this command out?
Does disclosure of usage pattern simply means that someone getting hold of the disk might be able to figure out how much space of the disk is occupied by my encrypted data?
Or might some resourceful secret agency be able to discover more private information?