1crypttab(5) File Formats Manual crypttab(5)
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6 /etc/crypttab - encrypted block device table
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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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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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87 cryptsetup(8)
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91 Jul 2006 crypttab(5)