crypttab(5)                                                        crypttab(5)

NAME

       /etc/crypttab - encrypted block device table

DESCRIPTION

       The  /etc/crypptab  file describes encrypted block devices that are set
       up during system boot.

       Empty lines and lines starting with the # character are ignored.   Each
       of  the remaining lines describes one encrypted block device, fields on
       the line are delimited by white space.  The first two fields are manda-
       tory, the remaining two are optional.

       The  first  field  contains  the  name of the resulting encrypted block
       device; the device is set up at /dev/mapper/name.

       The second field contains a path to the underlying  block  device.   If
       the  block  device  contains  a  LUKS signature, it is opened as a LUKS
       encrypted partition; otherwise it is assumed to be a raw dm-crypt  par-
       tition.

       The third field specifies the encryption password.  If the field is not
       present or the password is set to none, the password has to be manually
       entered  during  system  boot.  Otherwise the field is interpreted as a
       path to a file containing the encryption password.  For swap encryption
       /dev/urandom  can  be  used as the password file; using /dev/random may
       prevent boot completion if the system does not have enough  entropy  to
       generate a truly random encryption key.

       The  fourth  field,  if  present, is a comma-delimited list of options.
       The following options are recognized:

       cipher=cipher
              Specifies the cipher to use; see cryptsetup(8) for possible val-
              ues  and the default value of this option.  A cipher with unpre-
              dictable IV values,  such  as  aes-cbc-essiv:sha256,  is  recom-
              mended.

       size=size
              Specifies  the  key size in bits; see cryptsetup(8) for possible
              values and the default value of this option.

       hash=hash
              Specifies the hash to  use  for  password  hashing;  see  crypt-
              setup(8)  for  possible  values  and  the  default value of this
              option.

       verify If the the encryption password is read from console, it  has  to
              be entered twice (to prevent typos).

       swap   The encrypted block device will be used as a swap partition, and
              will be formatted as a  swap  partition  after  setting  up  the
              encrypted  block  device.   The  underlying block device will be
              formatted again as an unencrypted swap partition after  destroy-
              ing  the  encrypted block device.  (This allows sharing a single
              swap partition between operating system installations, with some
              of them encrypting the swap partitions and some of them not.)

              WARNING:  Using the swap option will destroy the contents of the
              named partition during every boot, so make sure  the  underlying
              block device is specified correctly.

       tmp    The  encrypted block device will be prepared for using it as tmp
              partition: it will be formatted using mke2fs and its root direc-
              tory  will  be  set  to  mode 01777.  The warning about the swap
              option applies here as well.

       No options can be specified for LUKS encrypted partitions.

COMPATIBILITY

       The /etc/crypptab file format is based on the Debian  cryptsetup  pack-
       age, and is intended to be compatible.

SEE ALSO

       cryptsetup(8)

                                   Jul 2006                        crypttab(5)