table of contents
CRYPTTAB(5) | crypttab | CRYPTTAB(5) |
NAME¶
crypttab - Configuration for encrypted block devices
SYNOPSIS¶
/etc/crypttab
DESCRIPTION¶
The /etc/crypttab 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 mandatory, the remaining two are optional.
Setting up encrypted block devices using this file supports three encryption modes: LUKS, TrueCrypt and plain. See cryptsetup(8) for more information about each mode. When no mode is specified in the options field and the block device contains a LUKS signature, it is opened as a LUKS device; otherwise, it is assumed to be in raw dm-crypt (plain mode) format.
The first field contains the name of the resulting encrypted block device; the device is set up within /dev/mapper/.
The second field contains a path to the underlying block device or file, or a specification of a block device via "UUID=" followed by the UUID.
The third field specifies the encryption password. If the field is not present or the password is set to "none" or "-", the password has to be manually entered during system boot. Otherwise, the field is interpreted as a absolute path to a file containing the encryption password. For swap encryption, /dev/urandom or the hardware device /dev/hw_random 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:
discard
cipher=
hash=
header=
keyfile-offset=
keyfile-size=
key-slot=
luks
_netdev
Hint: if this device is used for a mount point that is specified in fstab(5), the _netdev option should also be used for the mount point. Otherwise, a dependency loop might be created where the mount point will be pulled in by local-fs.target, while the service to configure the network is usually only started after the local file system has been mounted.
noauto
nofail
plain
read-only, readonly
size=
sector-size=
swap
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.
tcrypt
When this mode is used, the passphrase is read from the key file given in the third field. Only the first line of this file is read, excluding the new line character.
Note that the TrueCrypt format uses both passphrase and key files to derive a password for the volume. Therefore, the passphrase and all key files need to be provided. Use tcrypt-keyfile= to provide the absolute path to all key files. When using an empty passphrase in combination with one or more key files, use "/dev/null" as the password file in the third field.
tcrypt-hidden
This will map the hidden volume that is inside of the volume provided in the second field. Please note that there is no protection for the hidden volume if the outer volume is mounted instead. See cryptsetup(8) for more information on this limitation.
tcrypt-keyfile=
See the entry for tcrypt on the behavior of the passphrase and key files when using TrueCrypt encryption mode.
tcrypt-system
timeout=
x-systemd.device-timeout=
tmp
WARNING: Using the tmp option will destroy the contents of the named partition during every boot, so make sure the underlying block device is specified correctly.
tries=
verify
At early boot and when the system manager configuration is reloaded, this file is translated into native systemd units by systemd-cryptsetup-generator(8).
EXAMPLE¶
Example 1. /etc/crypttab example
Set up four encrypted block devices. One using LUKS for normal storage, another one for usage as a swap device and two TrueCrypt volumes.
luks UUID=2505567a-9e27-4efe-a4d5-15ad146c258b swap /dev/sda7 /dev/urandom swap truecrypt /dev/sda2 /etc/container_password tcrypt hidden /mnt/tc_hidden /dev/null tcrypt-hidden,tcrypt-keyfile=/etc/keyfile
SEE ALSO¶
systemd(1), systemd-cryptsetup@.service(8), systemd-cryptsetup-generator(8), fstab(5), cryptsetup(8), mkswap(8), mke2fs(8)
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