Abstract of the Device Mapper Plugin

The file /etc/conf/dm/mounts is read and each line evaluated as follows:

if the line doesn't describe the root filesystem and the root filesystem is not yet mounted, mount it.
check what we should do with the filesystem
- plain
  - Do nothing, just mount it as it is
- swap
  - This is an encrypted swapdevice:
  - Get 128 Byte of entropy from /dev/random
  - Get the md5sum of the entropy
  - Set up encryption with the md5sum and the device
  - Create a swapspace on the encrypted pseudodevice
  - Activate the swap
- encrypt
  - Read the passphrase from /dev/console
  - Check if the passphrase is shorter than 20 characters.
    - yes
    - Warn the user that the passphrase is very short. He can enter it again to use it anyways
  - ask for confirmation to avoid typos in the passphrase
  - setup encryption with dmsetup
  - do a sanity check by reading from the disk and writing to /dev/null
  - ask the user for permission to encrypt the data now
  - encrypt the data by reading from the disk and writing to the devicemapper
  - mount the filesystem and continue
- decrypt
  - Read the passphrase from /dev/console
  - ask for confirmation to avoid typos in the passphrase
  - setup encryption with dmsetup
  - do a sanity check by reading from the disk and writing to /dev/null
  - ask the user for permission to decrypt the data now
  - decrypt the data by reading from the devicemapper and writing to the disk
  - remove the devicemapper
  - mount the filesystem and continue