CRYPTSETUP(8) Maintenance Commands CRYPTSETUP(8)
cryptsetup - manage plain dm-crypt and LUKS encrypted volumes
cryptsetup <options> <action> <action args>
cryptsetup is used to conveniently setup dm-crypt managed device-
mapper mappings. These include plain dm-crypt volumes and LUKS
volumes. The difference is that LUKS uses a metadata header and
can hence offer more features than plain dm-crypt. On the other
hand, the header is visible and vulnerable to damage.
In addition, cryptsetup provides limited support for the use of
loop-AES volumes, TrueCrypt, VeraCrypt and BitLocker compatible
volumes.
Unless you understand the cryptographic background well, use
LUKS. With plain dm-crypt there are a number of possible user
errors that massively decrease security. While LUKS cannot fix
them all, it can lessen the impact for many of them.
A lot of good information on the risks of using encrypted
storage, on handling problems and on security aspects can be
found in the Cryptsetup FAQ. Read it. Nonetheless, some risks
deserve to be mentioned here.
Backup: Storage media die. Encryption has no influence on that.
Backup is mandatory for encrypted data as well, if the data has
any worth. See the Cryptsetup FAQ for advice on how to do a
backup of an encrypted volume.
Character encoding: If you enter a passphrase with special
symbols, the passphrase can change depending on character
encoding. Keyboard settings can also change, which can make blind
input hard or impossible. For example, switching from some ASCII
8-bit variant to UTF-8 can lead to a different binary encoding
and hence different passphrase seen by cryptsetup, even if what
you see on the terminal is exactly the same. It is therefore
highly recommended to select passphrase characters only from
7-bit ASCII, as the encoding for 7-bit ASCII stays the same for
all ASCII variants and UTF-8.
LUKS header: If the header of a LUKS volume gets damaged, all
data is permanently lost unless you have a header-backup. If a
key-slot is damaged, it can only be restored from a header-backup
or if another active key-slot with known passphrase is undamaged.
Damaging the LUKS header is something people manage to do with
surprising frequency. This risk is the result of a trade-off
between security and safety, as LUKS is designed for fast and
secure wiping by just overwriting header and key-slot area.
Previously used partitions: If a partition was previously used,
it is a very good idea to wipe filesystem signatures, data, etc.
before creating a LUKS or plain dm-crypt container on it. For a
quick removal of filesystem signatures, use "wipefs". Take care
though that this may not remove everything. In particular, MD
RAID signatures at the end of a device may survive. It also does
not remove data. For a full wipe, overwrite the whole partition
before container creation. If you do not know how to do that, the
cryptsetup FAQ describes several options.
The following are valid actions for all supported device types.
open <device> <name> --type <device_type>
Opens (creates a mapping with) <name> backed by device
<device>.
Device type can be plain, luks (default), luks1, luks2,
loopaes or tcrypt.
For backward compatibility there are open command aliases:
create (argument-order <name> <device>): open --type plain
plainOpen: open --type plain
luksOpen: open --type luks
loopaesOpen: open --type loopaes
tcryptOpen: open --type tcrypt
bitlkOpen: open --type bitlk
<options> are type specific and are described below for
individual device types. For create, the order of the
<name> and <device> options is inverted for historical
reasons, all other aliases use the standard <device>
<name> order.
close <name>
Removes the existing mapping <name> and wipes the key from
kernel memory.
For backward compatibility there are close command
aliases: remove, plainClose, luksClose, loopaesClose,
tcryptClose (all behaves exactly the same, device type is
determined automatically from active device).
<options> can be [--deferred] or [--cancel-deferred]
status <name>
Reports the status for the mapping <name>.
resize <name>
Resizes an active mapping <name>.
If --size (in 512-bytes sectors) or --device-size are not
specified, the size is computed from the underlying
device. For LUKS it is the size of the underlying device
without the area reserved for LUKS header (see data
payload offset in luksDump command). For plain crypt
device, the whole device size is used.
Note that this does not change the raw device geometry, it
just changes how many sectors of the raw device are
represented in the mapped device.
If cryptsetup detected volume key for active device loaded
in kernel keyring service, resize action would first try
to retrieve the key using a token and only if it failed
it'd ask for a passphrase to unlock a keyslot (LUKS) or to
derive a volume key again (plain mode). The kernel
keyring is used by default for LUKS2 devices.
With LUKS2 device additional <options> can be [--token-id,
--token-only, --key-slot, --key-file, --keyfile-size,
--keyfile-offset, --timeout, --disable-locks,
--disable-keyring].
refresh <name>
Refreshes parameters of active mapping <name>.
Updates parameters of active device <name> without need to
deactivate the device (and umount filesystem). Currently
it supports parameters refresh on following devices:
LUKS1, LUKS2 (including authenticated encryption), plain
crypt and loopaes.
Mandatory parameters are identical to those of an open
action for respective device type.
You may change following parameters on all devices
--perf-same_cpu_crypt, --perf-submit_from_crypt_cpus,
--perf-no_read_workqueue, --no_write_workqueue and
--allow-discards.
Refreshing device without any optional parameter will
refresh the device with default setting (respective to
device type).
LUKS2 only:
--integrity-no-journal parameter affects only LUKS2
devices with underlying dm-integrity device.
Adding option --persistent stores any combination of
device parameters above in LUKS2 metadata (only after
successful refresh operation).
--disable-keyring parameter refreshes a device with volume
key passed in dm-crypt driver.
reencrypt <device> or --active-name <name> [<new_name>]
Run resilient reencryption (LUKS2 device only).
There are 3 basic modes of operation:
• device reencryption (reencrypt)
• device encryption (reencrypt --encrypt)
• device decryption (reencrypt --decrypt)
<device> or --active-name <name> is mandatory parameter.
With <device> parameter cryptsetup looks up active
<device> dm mapping. If no active mapping is detected, it
starts offline reencryption otherwise online reencryption
takes place.
Reencryption process may be safely interrupted by a user
via SIGTERM signal (ctrl+c).
To resume already initialized or interrupted reencryption,
just run the cryptsetup reencrypt command again to
continue the reencryption operation. Reencryption may be
resumed with different --resilience or --hotzone-size
unless implicit datashift resilience mode is used
(reencrypt --encrypt with --reduce-device-size option).
If the reencryption process was interrupted abruptly
(reencryption process crash, system crash, poweroff) it
may require recovery. The recovery is currently run
automatically on next activation (action open) when
needed.
Optional parameter <new_name> takes effect only with
--encrypt option and it activates device <new_name>
immediately after encryption initialization gets finished.
That's useful when device needs to be ready as soon as
possible and mounted (used) before full data area
encryption is completed.
Action supports following additional <options> [--encrypt,
--decrypt, --device-size, --resilience, --resilience-hash,
--hotzone-size, --init-only, --resume-only,
--reduce-device-size, --master-key-file, --key-size].
Plain dm-crypt encrypts the device sector-by-sector with a
single, non-salted hash of the passphrase. No checks are
performed, no metadata is used. There is no formatting operation.
When the raw device is mapped (opened), the usual device
operations can be used on the mapped device, including filesystem
creation. Mapped devices usually reside in /dev/mapper/<name>.
The following are valid plain device type actions:
open --type plain <device> <name>
create <name> <device> (OBSOLETE syntax)
Opens (creates a mapping with) <name> backed by device
<device>.
<options> can be [--hash, --cipher, --verify-passphrase,
--sector-size, --key-file, --keyfile-offset, --key-size,
--offset, --skip, --size, --readonly, --shared,
--allow-discards, --refresh]
Example: 'cryptsetup open --type plain /dev/sda10 e1' maps
the raw encrypted device /dev/sda10 to the mapped
(decrypted) device /dev/mapper/e1, which can then be
mounted, fsck-ed or have a filesystem created on it.
LUKS, the Linux Unified Key Setup, is a standard for disk
encryption. It adds a standardized header at the start of the
device, a key-slot area directly behind the header and the bulk
data area behind that. The whole set is called a 'LUKS
container'. The device that a LUKS container resides on is
called a 'LUKS device'. For most purposes, both terms can be
used interchangeably. But note that when the LUKS header is at a
nonzero offset in a device, then the device is not a LUKS device
anymore, but has a LUKS container stored in it at an offset.
LUKS can manage multiple passphrases that can be individually
revoked or changed and that can be securely scrubbed from
persistent media due to the use of anti-forensic stripes.
Passphrases are protected against brute-force and dictionary
attacks by PBKDF2, which implements hash iteration and salting in
one function.
LUKS2 is a new version of header format that allows additional
extensions like different PBKDF algorithm or authenticated
encryption. You can format device with LUKS2 header if you
specify --type luks2 in luksFormat command. For activation, the
format is already recognized automatically.
Each passphrase, also called a key in this document, is
associated with one of 8 key-slots. Key operations that do not
specify a slot affect the first slot that matches the supplied
passphrase or the first empty slot if a new passphrase is added.
The <device> parameter can also be specified by a LUKS UUID in
the format UUID=<uuid>. Translation to real device name uses
symlinks in /dev/disk/by-uuid directory.
To specify a detached header, the --header parameter can be used
in all LUKS commands and always takes precedence over the
positional <device> parameter.
The following are valid LUKS actions:
luksFormat <device> [<key file>]
Initializes a LUKS partition and sets the initial
passphrase (for key-slot 0), either via prompting or via
<key file>. Note that if the second argument is present,
then the passphrase is taken from the file given there,
without the need to use the --key-file option. Also note
that for both forms of reading the passphrase from a file
you can give '-' as file name, which results in the
passphrase being read from stdin and the safety-question
being skipped.
You cannot call luksFormat on a device or filesystem that
is mapped or in use, e.g. mounted filesysem, used in LVM,
active RAID member etc. The device or filesystem has to be
un-mounted in order to call luksFormat.
To use LUKS2, specify --type luks2.
<options> can be [--hash, --cipher, --verify-passphrase,
--key-size, --key-slot, --key-file (takes precedence over
optional second argument), --keyfile-offset,
--keyfile-size, --use-random | --use-urandom, --uuid,
--master-key-file, --iter-time, --header,
--pbkdf-force-iterations, --force-password, --disable-
locks].
For LUKS2, additional <options> can be [--integrity,
--integrity-no-wipe, --sector-size, --label, --subsystem,
--pbkdf, --pbkdf-memory, --pbkdf-parallel,
--disable-locks, --disable-keyring, --luks2-metadata-size,
--luks2-keyslots-size, --keyslot-cipher,
--keyslot-key-size].
WARNING: Doing a luksFormat on an existing LUKS container
will make all data the old container permanently
irretrievable unless you have a header backup.
open --type luks <device> <name>
luksOpen <device> <name> (old syntax)
Opens the LUKS device <device> and sets up a mapping
<name> after successful verification of the supplied
passphrase.
First, the passphrase is searched in LUKS tokens. If it's
not found in any token and also the passphrase is not
supplied via --key-file, the command prompts for it
interactively.
<options> can be [--key-file, --keyfile-offset,
--keyfile-size, --readonly, --test-passphrase,
--allow-discards, --header, --key-slot, --master-key-file,
--token-id, --token-only, --disable-keyring,
--disable-locks, --type, --refresh,
--serialize-memory-hard-pbkdf].
luksSuspend <name>
Suspends an active device (all IO operations will block
and accesses to the device will wait indefinitely) and
wipes the encryption key from kernel memory. Needs kernel
2.6.19 or later.
After this operation you have to use luksResume to
reinstate the encryption key and unblock the device or
close to remove the mapped device.
WARNING: never suspend the device on which the cryptsetup
binary resides.
<options> can be [--header, --disable-locks].
luksResume <name>
Resumes a suspended device and reinstates the encryption
key. Prompts interactively for a passphrase if --key-file
is not given.
<options> can be [--key-file, --keyfile-size, --header,
--disable-keyring, --disable-locks, --type]
luksAddKey <device> [<key file with new key>]
Adds a new passphrase. An existing passphrase must be
supplied interactively or via --key-file. The new
passphrase to be added can be specified interactively or
read from the file given as positional argument.
NOTE: with --unbound option the action creates new unbound
LUKS2 keyslot. The keyslot cannot be used for device
activation. If you don't pass new key via
--master-key-file option, new random key is generated.
Existing passphrase for any active keyslot is not
required.
<options> can be [--key-file, --keyfile-offset,
--keyfile-size, --new-keyfile-offset, --new-keyfile-size,
--key-slot, --master-key-file, --force-password, --header,
--disable-locks, --iter-time, --pbkdf,
--pbkdf-force-iterations, --unbound, --type,
--keyslot-cipher, --keyslot-key-size].
luksRemoveKey <device> [<key file with passphrase to be removed>]
Removes the supplied passphrase from the LUKS device. The
passphrase to be removed can be specified interactively,
as the positional argument or via --key-file.
<options> can be [--key-file, --keyfile-offset,
--keyfile-size, --header, --disable-locks, --type]
WARNING: If you read the passphrase from stdin (without
further argument or with '-' as an argument to
--key-file), batch-mode (-q) will be implicitly switched
on and no warning will be given when you remove the last
remaining passphrase from a LUKS container. Removing the
last passphrase makes the LUKS container permanently
inaccessible.
luksChangeKey <device> [<new key file>]
Changes an existing passphrase. The passphrase to be
changed must be supplied interactively or via --key-file.
The new passphrase can be supplied interactively or in a
file given as positional argument.
If a key-slot is specified (via --key-slot), the
passphrase for that key-slot must be given and the new
passphrase will overwrite the specified key-slot. If no
key-slot is specified and there is still a free key-slot,
then the new passphrase will be put into a free key-slot
before the key-slot containing the old passphrase is
purged. If there is no free key-slot, then the key-slot
with the old passphrase is overwritten directly.
WARNING: If a key-slot is overwritten, a media failure
during this operation can cause the overwrite to fail
after the old passphrase has been wiped and make the LUKS
container inaccessible.
<options> can be [--key-file, --keyfile-offset,
--keyfile-size, --new-keyfile-offset, --iter-time,
--pbkdf, --pbkdf-force-iterations, --new-keyfile-size,
--key-slot, --force-password, --header, --disable-locks,
--type, --keyslot-cipher, --keyslot-key-size].
luksConvertKey <device>
Converts an existing LUKS2 keyslot to new pbkdf
parameters. The passphrase for keyslot to be converted
must be supplied interactively or via --key-file. If no
--pbkdf parameters are specified LUKS2 default pbkdf
values will apply.
If a keyslot is specified (via --key-slot), the passphrase
for that keyslot must be given. If no keyslot is specified
and there is still a free keyslot, then the new parameters
will be put into a free keyslot before the keyslot
containing the old parameters is purged. If there is no
free keyslot, then the keyslot with the old parameters is
overwritten directly.
WARNING: If a keyslot is overwritten, a media failure
during this operation can cause the overwrite to fail
after the old parameters have been wiped and make the LUKS
container inaccessible.
<options> can be [--key-file, --keyfile-offset,
--keyfile-size, --key-slot, --header, --disable-locks,
--iter-time, --pbkdf, --pbkdf-force-iterations,
--pbkdf-memory, --pbkdf-parallel, --keyslot-cipher,
--keyslot-key-size].
luksKillSlot <device> <key slot number>
Wipe the key-slot number <key slot> from the LUKS device.
Except running in batch-mode (-q) a remaining passphrase
must be supplied, either interactively or via --key-file.
This command can remove the last remaining key-slot, but
requires an interactive confirmation when doing so.
Removing the last passphrase makes a LUKS container
permanently inaccessible.
<options> can be [--key-file, --keyfile-offset,
--keyfile-size, --header, --disable-locks, --type].
WARNING: If you read the passphrase from stdin (without
further argument or with '-' as an argument to --key-
file), batch-mode (-q) will be implicitly switched on and
no warning will be given when you remove the last
remaining passphrase from a LUKS container. Removing the
last passphrase makes the LUKS container permanently
inaccessible.
NOTE: If there is no passphrase provided (on stdin or
through --key-file argument) and batch-mode (-q) is
active, the key-slot is removed without any other warning.
erase <device>
luksErase <device>
Erase all keyslots and make the LUKS container permanently
inaccessible. You do not need to provide any password for
this operation.
WARNING: This operation is irreversible.
luksUUID <device>
Print the UUID of a LUKS device.
Set new UUID if --uuid option is specified.
isLuks <device>
Returns true, if <device> is a LUKS device, false
otherwise. Use option -v to get human-readable feedback.
'Command successful.' means the device is a LUKS device.
By specifying --type you may query for specific LUKS
version.
luksDump <device>
Dump the header information of a LUKS device.
If the --dump-master-key option is used, the LUKS device
master key is dumped instead of the keyslot info. Together
with --master-key-file option, master key is dumped to a
file instead of standard output. Beware that the master
key cannot be changed without reencryption and can be used
to decrypt the data stored in the LUKS container without a
passphrase and even without the LUKS header. This means
that if the master key is compromised, the whole device
has to be erased or reencrypted to prevent further access.
Use this option carefully.
To dump the master key, a passphrase has to be supplied,
either interactively or via --key-file.
To dump unbound key (LUKS2 format only), --unbound
parameter, specific --key-slot id and proper passphrase
has to be supplied, either interactively or via
--key-file. Optional --master-key-file parameter enables
unbound keyslot dump to a file.
<options> can be [--dump-master-key, --key-file,
--keyfile-offset, --keyfile-size, --header,
--disable-locks, --master-key-file, --type, --unbound,
--key-slot].
WARNING: If --dump-master-key is used with --key-file and
the argument to --key-file is '-', no validation question
will be asked and no warning given.
luksHeaderBackup <device> --header-backup-file <file>
Stores a binary backup of the LUKS header and keyslot
area.
Note: Using '-' as filename writes the header backup to a
file named '-'.
WARNING: This backup file and a passphrase valid at the
time of backup allows decryption of the LUKS data area,
even if the passphrase was later changed or removed from
the LUKS device. Also note that with a header backup you
lose the ability to securely wipe the LUKS device by just
overwriting the header and key-slots. You either need to
securely erase all header backups in addition or overwrite
the encrypted data area as well. The second option is
less secure, as some sectors can survive, e.g. due to
defect management.
luksHeaderRestore <device> --header-backup-file <file>
Restores a binary backup of the LUKS header and keyslot
area from the specified file.
Note: Using '-' as filename reads the header backup from a
file named '-'.
WARNING: Header and keyslots will be replaced, only the
passphrases from the backup will work afterward.
This command requires that the master key size and data
offset of the LUKS header already on the device and of the
header backup match. Alternatively, if there is no LUKS
header on the device, the backup will also be written to
it.
token <add|remove|import|export> <device>
Action add creates new keyring token to enable auto-
activation of the device. For the auto-activation, the
passphrase must be stored in keyring with the specified
description. Usually, the passphrase should be stored in
user or user-session keyring. The token command is
supported only for LUKS2.
For adding new keyring token, option --key-description is
mandatory. Also, new token is assigned to key slot
specified with --key-slot option or to all active key
slots in the case --key-slot option is omitted.
To remove existing token, specify the token ID which
should be removed with --token-id option.
WARNING: The action token remove removes any token type,
not just keyring type from token slot specified by
--token-id option.
Action import can store arbitrary valid token json in
LUKS2 header. It may be passed via standard input or via
file passed in --json-file option. If you specify
--key-slot then successfully imported token is also
assigned to the key slot.
Action export writes requested token json to a file passed
with --json-file or to standard output.
<options> can be [--header, --token-id, --key-slot,
--key-description, --disable-locks, --disable-keyring,
--json-file].
convert <device> --type <format>
Converts the device between LUKS1 and LUKS2 format (if
possible). The conversion will not be performed if there
is an additional LUKS2 feature or LUKS1 has unsupported
header size.
Conversion (both directions) must be performed on inactive
device. There must not be active dm-crypt mapping
established for LUKS header requested for conversion.
--type option is mandatory with following accepted values:
luks1 or luks2.
WARNING: The convert action can destroy the LUKS header in
the case of a crash during conversion or if a media error
occurs. Always create a header backup before performing
this operation!
<options> can be [--header, --type].
config <device>
Set permanent configuration options (store to LUKS
header). The config command is supported only for LUKS2.
The permanent options can be --priority to set priority
(normal, prefer, ignore) for keyslot (specified by
--key-slot) or --label and --subsystem.
<options> can be [--priority, --label, --subsystem,
--key-slot, --header].
cryptsetup supports mapping loop-AES encrypted partition using a
compatibility mode.
open --type loopaes <device> <name> --key-file <keyfile>
loopaesOpen <device> <name> --key-file <keyfile> (old syntax)
Opens the loop-AES <device> and sets up a mapping <name>.
If the key file is encrypted with GnuPG, then you have to
use --key-file=- and decrypt it before use, e.g. like
this:
gpg --decrypt <keyfile> | cryptsetup loopaesOpen
--key-file=- <device> <name>
WARNING: The loop-AES extension cannot use the direct
input of key file on real terminal because the keys are
separated by end-of-line and only part of the multi-key
file would be read.
If you need it in script, just use the pipe redirection:
echo $keyfile | cryptsetup loopaesOpen --key-file=-
<device> <name>
Use --keyfile-size to specify the proper key length if
needed.
Use --offset to specify device offset. Note that the units
need to be specified in number of 512 byte sectors.
Use --skip to specify the IV offset. If the original
device used an offset and but did not use it in IV sector
calculations, you have to explicitly use --skip 0 in
addition to the offset parameter.
Use --hash to override the default hash function for
passphrase hashing (otherwise it is detected according to
key size).
<options> can be [--key-file, --key-size, --offset,
--skip, --hash, --readonly, --allow-discards, --refresh].
See also section 7 of the FAQ and http://loop-aes.sourceforge.net
for more information regarding loop-AES.
cryptsetup supports mapping of TrueCrypt, tcplay or VeraCrypt
(with --veracrypt option) encrypted partition using a native
Linux kernel API. Header formatting and TCRYPT header change is
not supported, cryptsetup never changes TCRYPT header on-device.
TCRYPT extension requires kernel userspace crypto API to be
available (introduced in Linux kernel 2.6.38). If you are
configuring kernel yourself, enable "User-space interface for
symmetric key cipher algorithms" in "Cryptographic API" section
(CRYPTO_USER_API_SKCIPHER .config option).
Because TCRYPT header is encrypted, you have to always provide
valid passphrase and keyfiles.
Cryptsetup should recognize all header variants, except legacy
cipher chains using LRW encryption mode with 64 bits encryption
block (namely Blowfish in LRW mode is not recognized, this is
limitation of kernel crypto API).
To recognize a VeraCrypt device use the --veracrypt option.
VeraCrypt is just extension of TrueCrypt header with increased
iteration count so unlocking can take quite a lot of time (in
comparison with TCRYPT device).
To open a VeraCrypt device with a custom Personal Iteration
Multiplier (PIM) value, additionally to --veracrypt use either
the --veracrypt-pim=<PIM> option to directly specify the PIM on
the command- line or use --veracrypt-query-pim to be prompted for
the PIM.
The PIM value affects the number of iterations applied during key
derivation. Please refer to
https://www.veracrypt.fr/en/Personal%20Iterations%20Multiplier%20%28PIM%29.html
for more detailed information.
NOTE: Activation with tcryptOpen is supported only for cipher
chains using LRW or XTS encryption modes.
The tcryptDump command should work for all recognized TCRYPT
devices and doesn't require superuser privilege.
To map system device (device with boot loader where the whole
encrypted system resides) use --tcrypt-system option. You can
use partition device as the parameter (parameter must be real
partition device, not an image in a file), then only this
partition is mapped.
If you have the whole TCRYPT device as a file image and you want
to map multiple partition encrypted with system encryption,
please create loopback mapping with partitions first (losetup -P,
see losetup(8) man page for more info), and use loop partition as
the device parameter.
If you use the whole base device as a parameter, one device for
the whole system encryption is mapped. This mode is available
only for backward compatibility with older cryptsetup versions
which mapped TCRYPT system encryption using the whole device.
To use hidden header (and map hidden device, if available), use
--tcrypt-hidden option.
To explicitly use backup (secondary) header, use --tcrypt-backup
option.
NOTE: There is no protection for a hidden volume if the outer
volume is mounted. The reason is that if there were any
protection, it would require some metadata describing what to
protect in the outer volume and the hidden volume would become
detectable.
open --type tcrypt <device> <name>
tcryptOpen <device> <name> (old syntax)
Opens the TCRYPT (a TrueCrypt-compatible) <device> and
sets up a mapping <name>.
<options> can be [--key-file, --tcrypt-hidden,
--tcrypt-system, --tcrypt-backup, --readonly,
--test-passphrase, --allow-discards, --veracrypt,
--veracrypt-pim, --veracrypt-query-pim, --header].
The keyfile parameter allows a combination of file content
with the passphrase and can be repeated. Note that using
keyfiles is compatible with TCRYPT and is different from
LUKS keyfile logic.
WARNING: Option --allow-discards cannot be combined with
option --tcrypt-hidden. For normal mapping, it can cause
the destruction of hidden volume (hidden volume appears as
unused space for outer volume so this space can be
discarded).
tcryptDump <device>
Dump the header information of a TCRYPT device.
If the --dump-master-key option is used, the TCRYPT device
master key is dumped instead of TCRYPT header info. Beware
that the master key (or concatenated master keys if cipher
chain is used) can be used to decrypt the data stored in
the TCRYPT container without a passphrase. This means
that if the master key is compromised, the whole device
has to be erased to prevent further access. Use this
option carefully.
<options> can be [--dump-master-key, --key-file,
--tcrypt-hidden, --tcrypt-system, --tcrypt-backup].
The keyfile parameter allows a combination of file content
with the passphrase and can be repeated.
See also https://en.wikipedia.org/wiki/TrueCrypt for more
information regarding TrueCrypt.
Please note that cryptsetup does not use TrueCrypt code, please
report all problems related to this compatibility extension to
the cryptsetup project.
cryptsetup supports mapping of BitLocker and BitLocker to Go
encrypted partition using a native Linux kernel API. Header
formatting and BITLK header changes are not supported, cryptsetup
never changes BITLK header on-device.
WARNING: This extension is EXPERIMENTAL.
BITLK extension requires kernel userspace crypto API to be
available (for details see TCRYPT section).
Cryptsetup should recognize all BITLK header variants, except
legacy header used in Windows Vista systems and partially
decrypted BitLocker devices. Activation of legacy devices
encrypted in CBC mode requires at least Linux kernel version 5.3
and for devices using Elephant diffuser kernel 5.6.
The bitlkDump command should work for all recognized BITLK
devices and doesn't require superuser privilege.
For unlocking with the open a password or a recovery passphrase
or a startup key must be provided.
Additionally unlocking using master key is supported. You must
provide BitLocker Full Volume Encryption Key (FVEK) using the
--master-key-file option. The key must be decrypted and without
the header (only 128/256/512 bits of key data depending on used
cipher and mode).
Other unlocking methods (TPM, SmartCard) are not supported.
open --type bitlk <device> <name>
bitlkOpen <device> <name> (old syntax)
Opens the BITLK (a BitLocker-compatible) <device> and sets
up a mapping <name>.
<options> can be [--key-file, --readonly,
--test-passphrase, --allow-discards --master-key-file].
bitlkDump <device>
Dump the header information of a BITLK device.
<options> can be [--dump-master-key --master-key-file].
Please note that cryptsetup does not use any Windows BitLocker
code, please report all problems related to this compatibility
extension to the cryptsetup project.
repair <device>
Tries to repair the device metadata if possible. Currently
supported only for LUKS device type.
This command is useful to fix some known benign LUKS
metadata header corruptions. Only basic corruptions of
unused keyslot are fixable. This command will only change
the LUKS header, not any key-slot data. You may enforce
LUKS version by adding --type option.
WARNING: Always create a binary backup of the original
header before calling this command.
benchmark <options>
Benchmarks ciphers and KDF (key derivation function).
Without parameters, it tries to measure few common
configurations.
To benchmark other ciphers or modes, you need to specify
--cipher and --key-size options or --hash for KDF test.
NOTE: This benchmark is using memory only and is only
informative. You cannot directly predict real storage
encryption speed from it.
For testing block ciphers, this benchmark requires kernel
userspace crypto API to be available (introduced in Linux
kernel 2.6.38). If you are configuring kernel yourself,
enable "User-space interface for symmetric key cipher
algorithms" in "Cryptographic API" section
(CRYPTO_USER_API_SKCIPHER .config option).
<options> can be [--cipher, --key-size, --hash].
--verbose, -v
Print more information on command execution.
--debug or --debug-json
Run in debug mode with full diagnostic logs. Debug output
lines are always prefixed by '#'. If --debug-json is
used, additional LUKS2 JSON data structures are printed.
--type <device-type>
Specifies required device type, for more info read BASIC
ACTIONS section.
--hash, -h <hash-spec>
Specifies the passphrase hash for open (for plain and
loopaes device types).
Specifies the hash used in the LUKS key setup scheme and
volume key digest for luksFormat. The specified hash is
used as hash-parameter for PBKDF2 and for the AF splitter.
The specified hash name is passed to the compiled-in
crypto backend. Different backends may support different
hashes. For luksFormat, the hash algorithm must provide
at least 160 bits of output, which excludes, e.g., MD5. Do
not use a non-crypto hash like "crc32" as this breaks
security.
Values compatible with old version of cryptsetup are
"ripemd160" for open --type plain and "sha1" for
luksFormat.
Use cryptsetup --help to show the defaults.
--cipher, -c <cipher-spec>
Set the cipher specification string.
cryptsetup --help shows the compiled-in defaults. The
current default in the distributed sources is "aes-cbc-
essiv:sha256" for plain dm-crypt and "aes-xts-plain64" for
LUKS.
If a hash is part of the cipher specification, then it is
used as part of the IV generation. For example, ESSIV
needs a hash function, while "plain64" does not and hence
none is specified.
For XTS mode you can optionally set a key size of 512 bits
with the -s option. Key size for XTS mode is twice that
for other modes for the same security level.
XTS mode requires kernel 2.6.24 or later and plain64
requires kernel 2.6.33 or later. More information can be
found in the FAQ.
--verify-passphrase, -y
When interactively asking for a passphrase, ask for it
twice and complain if both inputs do not match. Advised
when creating a regular mapping for the first time, or
when running luksFormat. Ignored on input from file or
stdin.
--key-file, -d name
Read the passphrase from file.
If the name given is "-", then the passphrase will be read
from stdin. In this case, reading will not stop at
newline characters.
With LUKS, passphrases supplied via --key-file are always
the existing passphrases requested by a command, except in
the case of luksFormat where --key-file is equivalent to
the positional key file argument.
If you want to set a new passphrase via key file, you have
to use a positional argument to luksAddKey.
See section NOTES ON PASSPHRASE PROCESSING for more
information.
--keyfile-offset value
Skip value bytes at the beginning of the key file. Works
with all commands that accept key files.
--keyfile-size, -l value
Read a maximum of value bytes from the key file. The
default is to read the whole file up to the compiled-in
maximum that can be queried with --help. Supplying more
data than the compiled-in maximum aborts the operation.
This option is useful to cut trailing newlines, for
example. If --keyfile-offset is also given, the size count
starts after the offset. Works with all commands that
accept key files.
--new-keyfile-offset value
Skip value bytes at the start when adding a new passphrase
from key file with luksAddKey.
--new-keyfile-size value
Read a maximum of value bytes when adding a new passphrase
from key file with luksAddKey. The default is to read the
whole file up to the compiled-in maximum length that can
be queried with --help. Supplying more than the compiled
in maximum aborts the operation. When
--new-keyfile-offset is also given, reading starts after
the offset.
--master-key-file
Use a master key stored in a file.
For luksFormat this allows creating a LUKS header with
this specific master key. If the master key was taken from
an existing LUKS header and all other parameters are the
same, then the new header decrypts the data encrypted with
the header the master key was taken from.
Action luksDump together with --dump-master-key option:
The volume (master) key is stored in a file instead of
being printed out to standard output.
WARNING: If you create your own master key, you need to
make sure to do it right. Otherwise, you can end up with a
low-entropy or otherwise partially predictable master key
which will compromise security.
For luksAddKey this allows adding a new passphrase without
having to know an existing one.
For open this allows one to open the LUKS device without
giving a passphrase.
--dump-master-key
For luksDump this option includes the master key in the
displayed information. Use with care, as the master key
can be used to bypass the passphrases, see also option
--master-key-file.
--json-file
Read token json from a file or write token to it. See
token action for more information. --json-file=- reads
json from standard input or writes it to standard output
respectively.
--use-random
--use-urandom
For luksFormat these options define which kernel random
number generator will be used to create the master key
(which is a long-term key).
See NOTES ON RANDOM NUMBER GENERATORS for more
information. Use cryptsetup --help to show the compiled-in
default random number generator.
WARNING: In a low-entropy situation (e.g. in an embedded
system), both selections are problematic. Using
/dev/urandom can lead to weak keys. Using /dev/random can
block a long time, potentially forever, if not enough
entropy can be harvested by the kernel.
--key-slot, -S <0-7>
For LUKS operations that add key material, this options
allows you to specify which key slot is selected for the
new key. This option can be used for luksFormat, and
luksAddKey.
In addition, for open, this option selects a specific key-
slot to compare the passphrase against. If the given
passphrase would only match a different key-slot, the
operation fails.
--key-size, -s <bits>
Sets key size in bits. The argument has to be a multiple
of 8. The possible key-sizes are limited by the cipher and
mode used.
See /proc/crypto for more information. Note that key-size
in /proc/crypto is stated in bytes.
This option can be used for open --type plain or
luksFormat. All other LUKS actions will use the key-size
specified in the LUKS header. Use cryptsetup --help to
show the compiled-in defaults.
--size, -b <number of 512 byte sectors>
Set the size of the device in sectors of 512 bytes. This
option is only relevant for the open and resize actions.
--offset, -o <number of 512 byte sectors>
Start offset in the backend device in 512-byte sectors.
This option is only relevant for the open action with
plain or loopaes device types or for LUKS devices in
luksFormat.
For LUKS, the --offset option sets the data offset
(payload) of data device and must be be aligned to
4096-byte sectors (must be multiple of 8). This option
cannot be combined with --align-payload option.
--skip, -p <number of 512 byte sectors>
Start offset used in IV calculation in 512-byte sectors
(how many sectors of the encrypted data to skip at the
beginning). This option is only relevant for the open
action with plain or loopaes device types.
Hence, if --offset n, and --skip s, sector n (the first
sector of the encrypted device) will get a sector number
of s for the IV calculation.
--device-size size[units]
Instead of real device size, use specified value.
With reencrypt action it means that only specified area
(from the start of the device to the specified size) will
be reencrypted.
With resize action it sets new size of the device.
If no unit suffix is specified, the size is in bytes.
Unit suffix can be S for 512 byte sectors, K/M/G/T (or
KiB,MiB,GiB,TiB) for units with 1024 base or KB/MB/GB/TB
for 1000 base (SI scale).
WARNING: This is destructive operation when used with
reencrypt command.
--readonly, -r
set up a read-only mapping.
--shared
Creates an additional mapping for one common ciphertext
device. Arbitrary mappings are supported. This option is
only relevant for the open --type plain action. Use
--offset, --size and --skip to specify the mapped area.
--pbkdf <PBKDF spec>
Set Password-Based Key Derivation Function (PBKDF)
algorithm for LUKS keyslot. The PBKDF can be: pbkdf2 (for
PBKDF2 according to RFC2898), argon2i for Argon2i or
argon2id for Argon2id (see
https://www.cryptolux.org/index.php/Argon2 for more info).
For LUKS1, only PBKDF2 is accepted (no need to use this
option). The default PBKDF2 for LUKS2 is set during
compilation time and is available in cryptsetup --help
output.
A PBKDF is used for increasing dictionary and brute-force
attack cost for keyslot passwords. The parameters can be
time, memory and parallel cost.
For PBKDF2, only time cost (number of iterations) applies.
For Argon2i/id, there is also memory cost (memory required
during the process of key derivation) and parallel cost
(number of threads that run in parallel during the key
derivation.
Note that increasing memory cost also increases time, so
the final parameter values are measured by a benchmark.
The benchmark tries to find iteration time (--iter-time)
with required memory cost --pbkdf-memory. If it is not
possible, the memory cost is decreased as well. The
parallel cost --pbkdf-parallel is constant, is is checked
against available CPU cores (if not available, it is
decreased) and the maximum parallel cost is 4.
You can see all PBKDF parameters for particular LUKS2
keyslot with luksDump command.
NOTE: If you do not want to use benchmark and want to
specify all parameters directly, use
--pbkdf-force-iterations with --pbkdf-memory and
--pbkdf-parallel. This will override the values without
benchmarking. Note it can cause extremely long unlocking
time. Use only in specific cases, for example, if you know
that the formatted device will be used on some small
embedded system. In this case, the LUKS PBKDF2 digest
will be set to the minimum iteration count.
--iter-time, -i <number of milliseconds>
The number of milliseconds to spend with PBKDF passphrase
processing. This option is only relevant for LUKS
operations that set or change passphrases, such as
luksFormat or luksAddKey. Specifying 0 as parameter
selects the compiled-in default.
--pbkdf-memory <number>
Set the memory cost for PBKDF (for Argon2i/id the number
represents kilobytes). Note that it is maximal value,
PBKDF benchmark or available physical memory can decrease
it. This option is not available for PBKDF2.
--pbkdf-parallel <number>
Set the parallel cost for PBKDF (number of threads, up to
4). Note that it is maximal value, it is decreased
automatically if CPU online count is lower. This option
is not available for PBKDF2.
--pbkdf-force-iterations <num>
Avoid PBKDF benchmark and set time cost (iterations)
directly. It can be used for LUKS/LUKS2 device only. See
--pbkdf option for more info.
--batch-mode, -q
Suppresses all confirmation questions. Use with care!
If the -y option is not specified, this option also
switches off the passphrase verification for luksFormat.
--progress-frequency <seconds>
Print separate line every <seconds> with wipe progress.
--timeout, -t <number of seconds>
The number of seconds to wait before timeout on passphrase
input via terminal. It is relevant every time a passphrase
is asked, for example for open, luksFormat or luksAddKey.
It has no effect if used in conjunction with --key-file.
This option is useful when the system should not stall if
the user does not input a passphrase, e.g. during boot.
The default is a value of 0 seconds, which means to wait
forever.
--tries, -T
How often the input of the passphrase shall be retried.
This option is relevant every time a passphrase is asked,
for example for open, luksFormat or luksAddKey. The
default is 3 tries.
--align-payload <number of 512 byte sectors>
Align payload at a boundary of value 512-byte sectors.
This option is relevant for luksFormat.
If not specified, cryptsetup tries to use the topology
info provided by the kernel for the underlying device to
get the optimal alignment. If not available (or the
calculated value is a multiple of the default) data is by
default aligned to a 1MiB boundary (i.e. 2048 512-byte
sectors).
For a detached LUKS header, this option specifies the
offset on the data device. See also the --header option.
WARNING: This option is DEPRECATED and has often
unexpected impact to the data offset and keyslot area size
(for LUKS2) due to the complex rounding. For fixed data
device offset use --offset option instead.
--uuid=UUID
Use the provided UUID for the luksFormat command instead
of generating a new one. Changes the existing UUID when
used with the luksUUID command.
The UUID must be provided in the standard UUID format,
e.g. 12345678-1234-1234-1234-123456789abc.
--allow-discards
Allow the use of discard (TRIM) requests for the device.
This option is only relevant for open action. This is
also not supported for LUKS2 devices with data integrity
protection.
WARNING: This command can have a negative security impact
because it can make filesystem-level operations visible on
the physical device. For example, information leaking
filesystem type, used space, etc. may be extractable from
the physical device if the discarded blocks can be located
later. If in doubt, do not use it.
A kernel version of 3.1 or later is needed. For earlier
kernels, this option is ignored.
--perf-same_cpu_crypt
Perform encryption using the same cpu that IO was
submitted on. The default is to use an unbound workqueue
so that encryption work is automatically balanced between
available CPUs. This option is only relevant for open
action.
NOTE: This option is available only for low-level dm-crypt
performance tuning, use only if you need a change to
default dm-crypt behaviour. Needs kernel 4.0 or later.
--perf-submit_from_crypt_cpus
Disable offloading writes to a separate thread after
encryption. There are some situations where offloading
write bios from the encryption threads to a single thread
degrades performance significantly. The default is to
offload write bios to the same thread. This option is
only relevant for open action.
NOTE: This option is available only for low-level dm-crypt
performance tuning, use only if you need a change to
default dm-crypt behaviour. Needs kernel 4.0 or later.
--perf-no_read_workqueue, --perf-no_write_workqueue
Bypass dm-crypt internal workqueue and process read or
write requests synchronously. This option is only
relevant for open action.
NOTE: These options are available only for low-level dm-
crypt performance tuning, use only if you need a change to
default dm-crypt behaviour. Needs kernel 5.9 or later.
--test-passphrase
Do not activate the device, just verify passphrase. This
option is only relevant for open action (the device
mapping name is not mandatory if this option is used).
--header <device or file storing the LUKS header>
Use a detached (separated) metadata device or file where
the LUKS header is stored. This option allows one to store
ciphertext and LUKS header on different devices.
This option is only relevant for LUKS devices and can be
used with the luksFormat, open, luksSuspend, luksResume,
status and resize commands.
For luksFormat with a file name as the argument to
--header, the file will be automatically created if it
does not exist. See the cryptsetup FAQ for header size
calculation.
For other commands that change the LUKS header (e.g.
luksAddKey), specify the device or file with the LUKS
header directly as the LUKS device.
If used with luksFormat, the --align-payload option is
taken as absolute sector alignment on ciphertext device
and can be zero.
WARNING: There is no check whether the ciphertext device
specified actually belongs to the header given. In fact,
you can specify an arbitrary device as the ciphertext
device for open with the --header option. Use with care.
--header-backup-file <file>
Specify file with header backup for luksHeaderBackup or
luksHeaderRestore actions.
--force-password
Do not use password quality checking for new LUKS
passwords.
This option applies only to luksFormat, luksAddKey and
luksChangeKey and is ignored if cryptsetup is built
without password quality checking support.
For more info about password quality check, see the manual
page for pwquality.conf(5) and passwdqc.conf(5).
--deferred
Defers device removal in close command until the last user
closes it.
--cancel-deferred
Removes a previously configured deferred device removal in
close command.
--disable-locks
Disable lock protection for metadata on disk. This option
is valid only for LUKS2 and ignored for other formats.
WARNING: Do not use this option unless you run cryptsetup
in a restricted environment where locking is impossible to
perform (where /run directory cannot be used).
--disable-keyring
Do not load volume key in kernel keyring and store it
directly in the dm-crypt target instead. This option is
supported only for the LUKS2 format.
--key-description <text>
Set key description in keyring for use with token command.
--priority <normal|prefer|ignore>
Set a priority for LUKS2 keyslot. The prefer priority
marked slots are tried before normal priority. The
ignored priority means, that slot is never used, if not
explicitly requested by --key-slot option.
--token-id
Specify what token to use in actions token, open or
resize. If omitted, all available tokens will be checked
before proceeding further with passphrase prompt.
--token-only
Do not proceed further with action (any of token, open or
resize) if token activation failed. Without the option,
action asks for passphrase to proceed further.
--sector-size <bytes>
Set sector size for use with disk encryption. It must be
power of two and in range 512 - 4096 bytes. The default is
512 bytes sectors. This option is available only in the
LUKS2 mode.
Note that if sector size is higher than underlying device
hardware sector and there is not integrity protection that
uses data journal, using this option can increase risk on
incomplete sector writes during a power fail.
If used together with --integrity option and dm-integrity
journal, the atomicity of writes is guaranteed in all
cases (but it cost write performance - data has to be
written twice).
Increasing sector size from 512 bytes to 4096 bytes can
provide better performance on most of the modern storage
devices and also with some hw encryption accelerators.
--iv-large-sectors
Count Initialization Vector (IV) in larger sector size (if
set) instead of 512 bytes sectors. This option can be used
only for open command and plain encryption type.
NOTE: This option does not have any performance or
security impact, use it only for accessing incompatible
existing disk images from other systems that require this
option.
--persistent
If used with LUKS2 devices and activation commands like
open or refresh, the specified activation flags are
persistently written into metadata and used next time
automatically even for normal activation. (No need to use
cryptab or other system configuration files.)
If you need to remove a persistent flag, use --persistent
without the flag you want to remove (e.g. to disable
persistently stored discard flag, use --persistent without
--allow-discards).
Only --allow-discards, --perf-same_cpu_crypt,
--perf-submit_from_crypt_cpus, --perf-no_read_workqueue,
--perf-no_write_workqueue and --integrity-no-journal can
be stored persistently.
--refresh
Refreshes an active device with new set of parameters. See
action refresh description for more details.
--label <LABEL>
--subsystem <SUBSYSTEM> Set label and subsystem
description for LUKS2 device, can be used in config and
format actions. The label and subsystem are optional
fields and can be later used in udev scripts for
triggering user actions once device marked by these labels
is detected.
--integrity <integrity algorithm>
Specify integrity algorithm to be used for authenticated
disk encryption in LUKS2.
WARNING: This extension is EXPERIMENTAL and requires dm-
integrity kernel target (available since kernel version
4.12). For native AEAD modes, also enable "User-space
interface for AEAD cipher algorithms" in "Cryptographic
API" section (CONFIG_CRYPTO_USER_API_AEAD .config option).
For more info, see AUTHENTICATED DISK ENCRYPTION section.
--luks2-metadata-size <size>
This option can be used to enlarge the LUKS2 metadata
(JSON) area. The size includes 4096 bytes for binary
metadata (usable JSON area is smaller of the binary area).
According to LUKS2 specification, only these values are
valid: 16, 32, 64, 128, 256, 512, 1024, 2048 and 4096 kB
The <size> can be specified with unit suffix (for example
128k).
--luks2-keyslots-size <size>
This option can be used to set specific size of the LUKS2
binary keyslot area (key material is encrypted there). The
value must be aligned to multiple of 4096 bytes with
maximum size 128MB. The <size> can be specified with unit
suffix (for example 128k).
--keyslot-cipher <cipher-spec>
This option can be used to set specific cipher encryption
for the LUKS2 keyslot area.
--keyslot-key-size <bits>
This option can be used to set specific key size for the
LUKS2 keyslot area.
--integrity-no-journal
Activate device with integrity protection without using
data journal (direct write of data and integrity tags).
Note that without journal power fail can cause non-atomic
write and data corruption. Use only if journalling is
performed on a different storage layer.
--integrity-no-wipe
Skip wiping of device authentication (integrity) tags. If
you skip this step, sectors will report invalid integrity
tag until an application write to the sector.
NOTE: Even some writes to the device can fail if the write
is not aligned to page size and page-cache initiates read
of a sector with invalid integrity tag.
--unbound
Creates new or dumps existing LUKS2 unbound keyslot. See
luksAddKey or luksDump actions for more details.
--tcrypt-hidden
--tcrypt-system --tcrypt-backup Specify which TrueCrypt
on-disk header will be used to open the device. See
TCRYPT section for more info.
--veracrypt
Allow VeraCrypt compatible mode. Only for TCRYPT
extension. See TCRYPT section for more info.
--veracrypt-pim
--veracrypt-query-pim Use a custom Personal Iteration
Multiplier (PIM) for VeraCrypt device. See TCRYPT section
for more info.
--serialize-memory-hard-pbkdf
Use a global lock to serialize unlocking of keyslots using
memory-hard PBKDF.
NOTE: This is (ugly) workaround for a specific situation
when multiple devices are activated in parallel and system
instead of reporting out of memory starts unconditionally
stop processes using out-of-memory killer.
DO NOT USE this switch until you are implementing boot
environment with parallel devices activation!
--encrypt
Initialize (and run) device encryption (reencrypt action
parameter)
--decrypt
Initialize (and run) device decryption (reencrypt action
parameter)
--init-only
Initialize reencryption (any variant) operation in LUKS2
metadata only and exit. If any reencrypt operation is
already initialized in metadata, the command with
--init-only parameter fails.
--resume-only
Resume reencryption (any variant) operation already
described in LUKS2 metadata. If no reencrypt operation is
initialized, the command with --resume-only parameter
fails. Useful for resuming reencrypt operation without
accidentally triggering new reencryption operation.
--resilience <mode>
Reencryption resilience mode can be one of checksum,
journal or none.
checksum: default mode, where individual checksums of
ciphertext hotzone sectors are stored, so the recovery
process can detect which sectors where already
reencrypted. It requires that the device sector write is
atomic.
journal: the hotzone is journaled in the binary area (so
the data are written twice).
none: performance mode. There is no protection and the
only way it's safe to interrupt the reencryption is
similar to old offline reencryption utility. (ctrl+c).
The option is ignored if reencryption with datashift mode
is in progress.
--resilience-hash <hash>
The hash algorithm used with "--resilience checksum" only.
The default hash is sha256. With other resilience modes,
the hash parameter is ignored.
--hotzone-size <size>
This option can be used to set an upper limit on the size
of reencryption area (hotzone). The <size> can be
specified with unit suffix (for example 50M). Note that
actual hotzone size may be less than specified <size> due
to other limitations (free space in keyslots area or
available memory).
--reduce-device-size <size>
Initialize LUKS2 reencryption with data device size
reduction (currently only --encrypt variant is supported).
Last <size> sectors of <device> will be used to properly
initialize device reencryption. That means any data at
last <size> sectors will be lost.
It could be useful if you added some space to underlying
partition or logical volume (so last <size> sectors
contains no data).
Recommended minimal size is twice the default LUKS2 header
size (--reduce-device-size 32M) for --encrypt use case. Be
sure to have enough (at least --reduce-device-size value
of free space at the end of <device>).
WARNING: This is a destructive operation and cannot be
reverted. Use with extreme care - accidentally
overwritten filesystems are usually unrecoverable.
--version
Show the program version.
--usage
Show short option help.
--help, -?
Show help text and default parameters.
Example 1: Create LUKS 2 container on block device /dev/sdX.
sudo cryptsetup --type luks2 luksFormat /dev/sdX
Example 2: Add an additional passphrase to key slot 5.
sudo cryptsetup luksAddKey --key-slot 5 /dev/sdX
Example 3: Create LUKS header backup and save it to file.
sudo cryptsetup luksHeaderBackup /dev/sdX --header-backup-
file /var/tmp/NameOfBackupFile
Example 4: Open LUKS contaner on /dev/sdX and map it to
sdX_crypt.
sudo cryptsetup open /dev/sdX sdX_crypt
WARNING: The command in example 5 will erase all key slots. Your
cannot use your luks container afterwards anymore unless you have
a backup to restore.
Example 5: Erase all key slots on /dev/sdX.
sudo cryptsetup erase /dev/sdX
Example 6: Restore LUKS header from backup file.
sudo cryptsetup luksHeaderRestore /dev/sdX --header-
backup-file /var/tmp/NameOfBackupFile
Cryptsetup returns 0 on success and a non-zero value on error.
Error codes are: 1 wrong parameters, 2 no permission (bad
passphrase), 3 out of memory, 4 wrong device specified, 5 device
already exists or device is busy.
Note that no iterated hashing or salting is done in plain mode.
If hashing is done, it is a single direct hash. This means that
low-entropy passphrases are easy to attack in plain mode.
From a terminal: The passphrase is read until the first newline,
i.e. '\n'. The input without the newline character is processed
with the default hash or the hash specified with --hash. The
hash result will be truncated to the key size of the used cipher,
or the size specified with -s.
From stdin: Reading will continue until a newline (or until the
maximum input size is reached), with the trailing newline
stripped. The maximum input size is defined by the same compiled-
in default as for the maximum key file size and can be
overwritten using --keyfile-size option.
The data read will be hashed with the default hash or the hash
specified with --hash. The hash result will be truncated to the
key size of the used cipher, or the size specified with -s.
Note that if --key-file=- is used for reading the key from stdin,
trailing newlines are not stripped from the input.
If "plain" is used as argument to --hash, the input data will not
be hashed. Instead, it will be zero padded (if shorter than the
key size) or truncated (if longer than the key size) and used
directly as the binary key. This is useful for directly
specifying a binary key. No warning will be given if the amount
of data read from stdin is less than the key size.
From a key file: It will be truncated to the key size of the used
cipher or the size given by -s and directly used as a binary key.
WARNING: The --hash argument is being ignored. The --hash option
is usable only for stdin input in plain mode.
If the key file is shorter than the key, cryptsetup will quit
with an error. The maximum input size is defined by the same
compiled-in default as for the maximum key file size and can be
overwritten using --keyfile-size option.
LUKS uses PBKDF2 to protect against dictionary attacks and to
give some protection to low-entropy passphrases (see RFC 2898 and
the cryptsetup FAQ).
From a terminal: The passphrase is read until the first newline
and then processed by PBKDF2 without the newline character.
From stdin: LUKS will read passphrases from stdin up to the first
newline character or the compiled-in maximum key file length. If
--keyfile-size is given, it is ignored.
From key file: The complete keyfile is read up to the compiled-in
maximum size. Newline characters do not terminate the input. The
--keyfile-size option can be used to limit what is read.
Passphrase processing: Whenever a passphrase is added to a LUKS
header (luksAddKey, luksFormat), the user may specify how much
the time the passphrase processing should consume. The time is
used to determine the iteration count for PBKDF2 and higher times
will offer better protection for low-entropy passphrases, but
open will take longer to complete. For passphrases that have
entropy higher than the used key length, higher iteration times
will not increase security.
The default setting of one or two seconds is sufficient for most
practical cases. The only exception is a low-entropy passphrase
used on a device with a slow CPU, as this will result in a low
iteration count. On a slow device, it may be advisable to
increase the iteration time using the --iter-time option in order
to obtain a higher iteration count. This does slow down all later
luksOpen operations accordingly.
LUKS checks for a valid passphrase when an encrypted partition is
unlocked. The behavior of plain dm-crypt is different. It will
always decrypt with the passphrase given. If the given passphrase
is wrong, the device mapped by plain dm-crypt will essentially
still contain encrypted data and will be unreadable.
The available combinations of ciphers, modes, hashes and key
sizes depend on kernel support. See /proc/crypto for a list of
available options. You might need to load additional kernel
crypto modules in order to get more options.
For the --hash option, if the crypto backend is libgcrypt, then
all algorithms supported by the gcrypt library are available.
For other crypto backends, some algorithms may be missing.
Mathematics can't be bribed. Make sure you keep your passphrases
safe. There are a few nice tricks for constructing a fallback,
when suddenly out of the blue, your brain refuses to cooperate.
These fallbacks need LUKS, as it's only possible with LUKS to
have multiple passphrases. Still, if your attacker model does not
prevent it, storing your passphrase in a sealed envelope
somewhere may be a good idea as well.
Random Number Generators (RNG) used in cryptsetup are always the
kernel RNGs without any modifications or additions to data stream
produced.
There are two types of randomness cryptsetup/LUKS needs. One type
(which always uses /dev/urandom) is used for salts, the AF
splitter and for wiping deleted keyslots.
The second type is used for the volume (master) key. You can
switch between using /dev/random and /dev/urandom here, see
--use-random and --use-urandom options. Using /dev/random on a
system without enough entropy sources can cause luksFormat to
block until the requested amount of random data is gathered. In a
low-entropy situation (embedded system), this can take a very
long time and potentially forever. At the same time, using
/dev/urandom in a low-entropy situation will produce low-quality
keys. This is a serious problem, but solving it is out of scope
for a mere man-page. See urandom(4) for more information.
Since Linux kernel version 4.12 dm-crypt supports authenticated
disk encryption.
Normal disk encryption modes are length-preserving (plaintext
sector is of the same size as a ciphertext sector) and can
provide only confidentiality protection, but not
cryptographically sound data integrity protection.
Authenticated modes require additional space per-sector for
authentication tag and use Authenticated Encryption with
Additional Data (AEAD) algorithms.
If you configure LUKS2 device with data integrity protection,
there will be an underlying dm-integrity device, which provides
additional per-sector metadata space and also provide data
journal protection to ensure atomicity of data and metadata
update. Because there must be additional space for metadata and
journal, the available space for the device will be smaller than
for length-preserving modes.
The dm-crypt device then resides on top of such a dm-integrity
device. All activation and deactivation of this device stack is
performed by cryptsetup, there is no difference in using luksOpen
for integrity protected devices. If you want to format LUKS2
device with data integrity protection, use --integrity option.
Since dm-integrity doesn't support discards (TRIM), dm-crypt
device on top of it inherits this, so integrity protection mode
doesn't support discards either.
Some integrity modes requires two independent keys (key for
encryption and for authentication). Both these keys are stored in
one LUKS keyslot.
WARNING: All support for authenticated modes is experimental and
there are only some modes available for now. Note that there are
a very few authenticated encryption algorithms that are suitable
for disk encryption.
Cryptsetup is usually used directly on a block device (disk
partition or LVM volume). However, if the device argument is a
file, cryptsetup tries to allocate a loopback device and map it
into this file. This mode requires Linux kernel 2.6.25 or more
recent which supports the loop autoclear flag (loop device is
cleared on the last close automatically). Of course, you can
always map a file to a loop-device manually. See the cryptsetup
FAQ for an example.
When device mapping is active, you can see the loop backing file
in the status command output. Also see losetup(8).
The LUKS2 on-disk metadata is updated in several steps and to
achieve proper atomic update, there is a locking mechanism. For
an image in file, code uses flock(2) system call. For a block
device, lock is performed over a special file stored in a locking
directory (by default /run/lock/cryptsetup). The locking
directory should be created with the proper security context by
the distribution during the boot-up phase. Only LUKS2 uses
locks, other formats do not use this mechanism.
The reload action is no longer supported. Please use dmsetup(8)
if you need to directly manipulate with the device mapping table.
The luksDelKey was replaced with luksKillSlot.
Report bugs, including ones in the documentation, on the
cryptsetup mailing list at <dm-crypt@saout.de> or in the 'Issues'
section on LUKS website. Please attach the output of the failed
command with the --debug option added.
cryptsetup originally written by Jana Saout <jana@saout.de>
The LUKS extensions and original man page were written by Clemens
Fruhwirth <clemens@endorphin.org>.
Man page extensions by Milan Broz <gmazyland@gmail.com>.
Man page rewrite and extension by Arno Wagner <arno@wagner.name>.
Copyright © 2004 Jana Saout
Copyright © 2004-2006 Clemens Fruhwirth
Copyright © 2012-2014 Arno Wagner
Copyright © 2009-2020 Red Hat, Inc.
Copyright © 2009-2020 Milan Broz
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR
A PARTICULAR PURPOSE.
The LUKS website at https://gitlab.com/cryptsetup/cryptsetup/
The cryptsetup FAQ, contained in the distribution package and
online at
https://gitlab.com/cryptsetup/cryptsetup/wikis/FrequentlyAskedQuestions
The cryptsetup mailing list and list archive, see FAQ entry 1.6.
The LUKS on-disk format specification available at
https://gitlab.com/cryptsetup/cryptsetup/wikis/Specification
This page is part of the Cryptsetup ((open-source disk
encryption)) project. Information about the project can be found
at ⟨https://gitlab.com/cryptsetup/cryptsetup⟩. If you have a bug
report for this manual page, send it to dm-crypt@saout.de. This
page was obtained from the project's upstream Git repository
⟨https://gitlab.com/cryptsetup/cryptsetup.git⟩ on 2020-12-18.
(At that time, the date of the most recent commit that was found
in the repository was 2020-12-02.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
cryptsetup January 2019 CRYPTSETUP(8)
Pages that refer to this page: homectl(1), systemd-cryptenroll(1), crypttab(5), cryptsetup-reencrypt(8), fsadm(8), integritysetup(8), systemd-cryptsetup-generator(8), systemd-cryptsetup@.service(8), systemd-gpt-auto-generator(8), systemd-makefs@.service(8)
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