crypttab(5)

1crypttab(5)                   File Formats Manual                  crypttab(5)
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NAME

6       /etc/crypttab - encrypted block device table
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DESCRIPTION

10       The  /etc/crypptab  file describes encrypted block devices that are set
11       up during system boot.
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13       Empty lines and lines starting with the # character are ignored.   Each
14       of  the remaining lines describes one encrypted block device, fields on
15       the line are delimited by white space.  The first two fields are manda‐
16       tory, the remaining two are optional.
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18       The  first  field  contains  the  name of the resulting encrypted block
19       device; the device is set up at /dev/mapper/name.
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21       The second field contains a path to the underlying  block  device.   If
22       the  block  device  contains  a  LUKS signature, it is opened as a LUKS
23       encrypted partition; otherwise it is assumed to be a raw dm-crypt  par‐
24       tition.
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26       The third field specifies the encryption password.  If the field is not
27       present or the password is set to none, the password has to be manually
28       entered  during  system  boot.  Otherwise the field is interpreted as a
29       path to a file containing the encryption password.  For swap encryption
30       /dev/urandom  can  be  used as the password file; using /dev/random may
31       prevent boot completion if the system does not have enough  entropy  to
32       generate a truly random encryption key.
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34       The  fourth  field,  if  present, is a comma-delimited list of options.
35       The following options are recognized:
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37       cipher=cipher
38              Specifies the cipher to use; see cryptsetup(8) for possible val‐
39              ues  and the default value of this option.  A cipher with unpre‐
40              dictable IV values,  such  as  aes-cbc-essiv:sha256,  is  recom‐
41              mended.
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44       size=size
45              Specifies  the  key size in bits; see cryptsetup(8) for possible
46              values and the default value of this option.
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49       hash=hash
50              Specifies the hash to  use  for  password  hashing;  see  crypt‐
51              setup(8)  for  possible  values  and  the  default value of this
52              option.
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55       verify If the the encryption password is read from console, it  has  to
56              be entered twice (to prevent typos).
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59       swap   The encrypted block device will be used as a swap partition, and
60              will be formatted as a  swap  partition  after  setting  up  the
61              encrypted  block  device.   The  underlying block device will be
62              formatted again as an unencrypted swap partition after  destroy‐
63              ing  the  encrypted block device.  (This allows sharing a single
64              swap partition between operating system installations, with some
65              of them encrypting the swap partitions and some of them not.)
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67              WARNING:  Using the swap option will destroy the contents of the
68              named partition during every boot, so make sure  the  underlying
69              block device is specified correctly.
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72       tmp    The  encrypted block device will be prepared for using it as tmp
73              partition: it will be formatted using mke2fs and its root direc‐
74              tory  will  be  set  to  mode 01777.  The warning about the swap
75              option applies here as well.
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78       No options can be specified for LUKS encrypted partitions.
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COMPATIBILITY

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

DESCRIPTION

COMPATIBILITY

SEE ALSO