cryptsetup
CRYPTSETUP(8) Maintenance Commands CRYPTSETUP(8)
NAME
cryptsetup - manage plain dm-crypt and LUKS encrypted volumes
SYNOPSIS
cryptsetup <options> <action> <action args>
DESCRIPTION
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.
PLAIN DM-CRYPT OR LUKS?
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.
WARNINGS
A lot of good information on the risks of using encrypted storage, on
handling problems and on security aspects can be found in the Crypt-
setup 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 set-
tings 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 ac-
tive 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 creat-
ing 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.
BASIC ACTIONS
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 individ-
ual device types. For create, the order of the <name> and <de-
vice> 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 ker-
nel memory.
For backward compatibility there are close command aliases: re-
move, plainClose, luksClose, loopaesClose, tcryptClose (all be-
haves 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 speci-
fied, the size is computed from the underlying device. For LUKS
it is the size of the underlying device without the area re-
served for LUKS header (see data payload offset in luksDump com-
mand). 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 re-
trieve 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, --to-
ken-only, --token-type, --key-slot, --key-file, --keyfile-size,
--keyfile-offset, --timeout, --disable-external-tokens, --dis-
able-locks, --disable-keyring].
refresh <name>
Refreshes parameters of active mapping <name>.
Updates parameters of active device <name> without need to deac-
tivate 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, --perf-no_write_workqueue and --allow-dis-
cards.
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 pa-
rameters 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:
o device reencryption (reencrypt)
o device encryption (reencrypt --encrypt)
o 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 reen-
cryption operation. Reencryption may be resumed with different
--resilience or --hotzone-size unless implicit datashift re-
silience mode is used (reencrypt --encrypt with --reduce-device-
size option).
If the reencryption process was interrupted abruptly (reencryp-
tion process crash, system crash, poweroff) it may require re-
covery. The recovery is currently run automatically on next ac-
tivation (action open) when needed.
Optional parameter <new_name> takes effect only with --encrypt
option and it activates device <new_name> immediately after en-
cryption 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, --de-
crypt, --device-size, --resilience, --resilience-hash, --hot-
zone-size, --init-only, --resume-only, --reduce-device-size,
--master-key-file, --key-size].
PLAIN MODE
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, --sec-
tor-size, --key-file, --keyfile-offset, --key-size, --offset,
--skip, --size, --readonly, --shared, --allow-discards, --re-
fresh]
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 EXTENSION
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 con-
tainer 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 de-
vice 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 it-
eration and salting in one function.
LUKS2 is a new version of header format that allows additional exten-
sions 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 for-
mat 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 re-
sults 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 op-
tional second argument), --keyfile-offset, --keyfile-size,
--use-random | --use-urandom, --uuid, --master-key-file,
--iter-time, --header, --pbkdf-force-iterations, --force-pass-
word, --disable-locks].
For LUKS2, additional <options> can be [--integrity, --integ-
rity-no-wipe, --sector-size, --label, --subsystem, --pbkdf,
--pbkdf-memory, --pbkdf-parallel, --disable-locks, --dis-
able-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> af-
ter 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, --to-
ken-type, --disable-external-tokens, --disable-keyring, --dis-
able-locks, --type, --refresh, --serialize-memory-hard-pbkdf].
luksSuspend <name>
Suspends an active device (all IO operations will block and ac-
cesses to the device will wait indefinitely) and wipes the en-
cryption 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, --dis-
able-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, --mas-
ter-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 con-
tainer. 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 over-
write 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 inaccessi-
ble.
<options> can be [--key-file, --keyfile-offset, --keyfile-size,
--new-keyfile-offset, --iter-time, --pbkdf, --pbkdf-force-itera-
tions, --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 interac-
tively 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 param-
eters 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 pa-
rameters have been wiped and make the LUKS container inaccessi-
ble.
<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 sup-
plied, 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 con-
tainer. 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 inac-
cessible. You do not need to provide any password for this op-
eration.
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 success-
ful.' 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 --mas-
ter-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 fur-
ther 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 --mas-
ter-key-file parameter enables unbound keyslot dump to a file.
To dump LUKS2 JSON metadata (without basic heade information
like UUID) use --dump-json-metadata option.
<options> can be [--dump-master-key, --dump-json-metadata,
--key-file, --keyfile-offset, --keyfile-size, --header, --dis-
able-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 se-
curely 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 manda-
tory. 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 op-
tion.
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 success-
fully 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-de-
scription, --disable-external-tokens, --disable-locks, --dis-
able-keyring, --json-file].
convert <device> --type <format>
Converts the device between LUKS1 and LUKS2 format (if possi-
ble). The conversion will not be performed if there is an addi-
tional LUKS2 feature or LUKS1 has unsupported header size.
Conversion (both directions) must be performed on inactive de-
vice. 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].
loop-AES EXTENSION
cryptsetup supports mapping loop-AES encrypted partition using a com-
patibility 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 param-
eter.
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.
TCRYPT (TrueCrypt-compatible and VeraCrypt) EXTENSION
cryptsetup supports mapping of TrueCrypt, tcplay or VeraCrypt 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 algo-
rithms" in "Cryptographic API" section (CRYPTO_USER_API_SKCIPHER .con-
fig 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).
VeraCrypt is just extension of TrueCrypt header with increased itera-
tion 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, 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 deri-
vation. Please refer to https://www.veracrypt.fr/en/Personal%20Itera-
tions%20Multiplier%20%28PIM%29.html for more detailed information.
If you need to disable VeraCrypt device support, use --disable-ver-
acrypt option.
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 de-
vice 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 op-
tion.
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 re-
quire 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-dis-
cards, --disable-veracrypt, --veracrypt-pim, --ver-
acrypt-query-pim, --header, --cipher, --hash].
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.
If --PBKDF2 variants with the specified hash algorithms are
checked. This could speed up unlocking the device (but also it
reveals some information about the container).
If you use --header in combination with hidden or system op-
tions, the header file must contain specific headers on the same
positions as the original encrypted container.
WARNING: Option --allow-discards cannot be combined with option
--tcrypt-hidden. For normal mapping, it can cause the destruc-
tion 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 mas-
ter 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 com-
promised, the whole device has to be erased to prevent further
access. Use this option carefully.
<options> can be [--dump-master-key, --key-file, --tcrypt-hid-
den, --tcrypt-system, --tcrypt-backup, --cipher, --hash].
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.
BITLK (Windows BitLocker-compatible) EXTENSION (EXPERIMENTAL)
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 dif-
fuser 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.
MISCELLANEOUS
repair <device>
Tries to repair the device metadata if possible. Currently sup-
ported 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 op-
tion.
It also repairs (upgrades) LUKS2 reencryption metadata by adding
metadata digest that protects it against malicious changes.
If LUKS2 reencryption was interrupted in the middle of writting
reencryption segment the repair command can be used to perform
reencryption recovery so that reencryption can continue later.
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 --ci-
pher and --key-size options or --hash for KDF test.
NOTE: This benchmark is using memory only and is only informa-
tive. 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 "Crypto-
graphic API" section (CRYPTO_USER_API_SKCIPHER .config option).
<options> can be [--cipher, --key-size, --hash].
OPTIONS
--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 charac-
ters.
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 spe-
cific 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 vol-
ume (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-en-
tropy or otherwise partially predictable master key which will
compromise security.
For luksAddKey this allows adding a new passphrase without hav-
ing to know an existing one.
For open this allows one to open the LUKS device without giving
a passphrase.
--dump-json-metadata
For luksDump (LUKS2 only) this option prints content of LUKS2
header JSON metadata area.
--dump-master-key
For luksDump this option includes the master key in the dis-
played 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 ac-
tion for more information. --json-file=- reads json from stan-
dard 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 sys-
tem), both selections are problematic. Using /dev/urandom can
lead to weak keys. Using /dev/random can block a long time, po-
tentially forever, if not enough entropy can be harvested by the
kernel.
--key-slot, -S <0-N>
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.
Maximum number of key slots depends on LUKS version. LUKS1 can
have up to 8 key slots. LUKS2 can have up to 32 key slots based
on key slot area size and key size, but a valid key slot ID can
always be between 0 and 31 for LUKS2.
--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 de-
faults.
--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 reen-
crypted.
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 fi-
nal 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 con-
stant and is checked against available CPU cores.
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 embed-
ded system.
MINIMAL AND MAXIMAL PBKDF COSTS: For PBKDF2, the minimum itera-
tion count is 1000 and maximum is 4294967295 (maximum for 32bit
unsigned integer). Memory and parallel costs are unused for
PBKDF2. For Argon2i and Argon2id, minimum iteration count (CPU
cost) is 4 and maximum is 4294967295 (maximum for 32bit unsigned
integer). Minimum memory cost is 32 KiB and maximum is 4 GiB.
(Limited by addresable memory on some CPU platforms.) If the
memory cost parameter is benchmarked (not specified by a parame-
ter) it is always in range from 64 MiB to 1 GiB. The parallel
cost minimum is 1 and maximum 4 (if enough CPUs cores are avail-
able, otherwise it is decreased).
--iter-time, -i <number of milliseconds>
The number of milliseconds to spend with PBKDF passphrase pro-
cessing. 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 repre-
sents kilobytes). Note that it is maximal value, PBKDF bench-
mark 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 ef-
fect 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 op-
tion is relevant for luksFormat.
If not specified, cryptsetup tries to use the topology info pro-
vided by the kernel for the underlying device to get the optimal
alignment. If not available (or the calculated value is a mul-
tiple 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 im-
pact 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 gen-
erating 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 sup-
ported for LUKS2 devices with data integrity protection.
WARNING: This command can have a negative security impact be-
cause 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 de-
vice 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 op-
tion is only relevant for open action.
NOTE: This option is available only for low-level dm-crypt per-
formance 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 sig-
nificantly. 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 per-
formance 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 re-
quests synchronously. This option is only relevant for open ac-
tion.
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 cipher-
text 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. luksAdd-
Key), 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 speci-
fied 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 luk-
sHeaderRestore 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-external-tokens
Disable loading of plugins for external LUKS2 tokens.
--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 re-
size) if token activation failed. Without the option, action
asks for passphrase to proceed further.
--token-type
Restrict tokens eligible for operation to specific token type
(name). Mostly useful when no --token-id is specified.
--sector-size <bytes>
Set sector size for use with disk encryption. It must be power
of two and in range 512 - 4096 bytes. This option is available
only in the LUKS2 or plain modes.
The default for plain mode is 512 bytes. For LUKS2 devices it's
established during luksFormat operation based on parameters pro-
vided by underlying data device. For native 4K block devices
it's 4096 bytes. For 4K/512e (4K physical sector size with 512
bytes emulation) it's 4096 bytes. For drives reporting only 512
bytes block size it remains 512 bytes. If data device is regular
file put in filesystem it's 4096 bytes.
Note that if sector size is higher than underlying device hard-
ware sector and there is not integrity protection that uses data
journal, using this option can increase risk on incomplete sec-
tor writes during a power fail.
If used together with --integrity option and dm-integrity jour-
nal, 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 im-
pact, use it only for accessing incompatible existing disk im-
ages 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 configura-
tion files.)
If you need to remove a persistent flag, use --persistent with-
out 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-sub-
mit_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 ac-
tion 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 la-
bel 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-integ-
rity 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 (CON-
FIG_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 sec-
tor with invalid integrity tag.
--unbound
Creates new or dumps existing LUKS2 unbound keyslot. See luksAd-
dKey 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
This option is ignored as VeraCrypt compatible mode is supported
by default.
--disable-veracrypt
This option can be used to disable VeraCrypt compatible mode
(only TrueCrypt devices are recognized). Only for TCRYPT exten-
sion. 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 mem-
ory-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 environ-
ment with parallel devices activation!
--encrypt
Initialize (and run) device encryption (reencrypt action parame-
ter)
--decrypt
Initialize (and run) device decryption (reencrypt action parame-
ter)
--init-only
Initialize reencryption (any variant) operation in LUKS2 meta-
data only and exit. If any reencrypt operation is already ini-
tialized 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 reen-
cryption 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 were 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 off-
line 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 ini-
tialize device reencryption. That means any data at last <size>
sectors will be lost.
It could be useful if you added some space to underlying parti-
tion 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
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 container 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
RETURN CODES
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.
NOTES ON PASSPHRASE PROCESSING FOR PLAIN MODE
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-en-
tropy 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 maxi-
mum key file size and can be overwritten using --keyfile-size option.
The data read will be hashed with the default hash or the hash speci-
fied 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 bi-
nary 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 ci-
pher 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 de-
fault as for the maximum key file size and can be overwritten using
--keyfile-size option.
NOTES ON PASSPHRASE PROCESSING FOR LUKS
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 new-
line character or the compiled-in maximum key file length. If --key-
file-size is given, it is ignored.
From key file: The complete keyfile is read up to the compiled-in maxi-
mum size. Newline characters do not terminate the input. The --key-
file-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 protec-
tion for low-entropy passphrases, but open will take longer to com-
plete. 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 prac-
tical 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.
INCOHERENT BEHAVIOR FOR INVALID PASSPHRASES/KEYS
LUKS checks for a valid passphrase when an encrypted partition is un-
locked. 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 en-
crypted data and will be unreadable.
NOTES ON SUPPORTED CIPHERS, MODES, HASHES AND KEY SIZES
The available combinations of ciphers, modes, hashes and key sizes de-
pend on kernel support. See /proc/crypto for a list of available op-
tions. 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 al-
gorithms supported by the gcrypt library are available. For other
crypto backends, some algorithms may be missing.
NOTES ON PASSPHRASES
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.
NOTES ON RANDOM NUMBER GENERATORS
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 be-
tween using /dev/random and /dev/urandom here, see --use-random and
--use-urandom options. Using /dev/random on a system without enough en-
tropy sources can cause luksFormat to block until the requested amount
of random data is gathered. In a low-entropy situation (embedded sys-
tem), 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.
AUTHENTICATED DISK ENCRYPTION (EXPERIMENTAL)
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 confiden-
tiality protection, but not cryptographically sound data integrity pro-
tection.
Authenticated modes require additional space per-sector for authentica-
tion 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 pro-
tected 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 encryp-
tion. You also cannot use CRC32 or any other non-cryptographic check-
sums (other than the special integrity mode "none"). If for some reason
you want to have integrity control without using authentication mode,
then you should separately configure dm-integrity independently of
LUKS2.
NOTES ON LOOPBACK DEVICE USE
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 automati-
cally). 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).
LUKS2 header locking
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 per-
formed 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.
DEPRECATED ACTIONS
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.
REPORTING BUGS
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 --de-
bug option added.
AUTHORS
cryptsetup originally written by Jana Saout <jana@saout.de>
The LUKS extensions and original man page were written by Clemens Fruh-
wirth <clemens@endorphin.org>.
Man page extensions by Milan Broz <gmazyland@gmail.com>.
Man page rewrite and extension by Arno Wagner <arno@wagner.name>.
COPYRIGHT
Copyright (C) 2004 Jana Saout
Copyright (C) 2004-2006 Clemens Fruhwirth
Copyright (C) 2012-2014 Arno Wagner
Copyright (C) 2009-2021 Red Hat, Inc.
Copyright (C) 2009-2021 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.
SEE ALSO
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 version 1 on-disk format specification available at
https://gitlab.com/cryptsetup/cryptsetup/wikis/Specification and LUKS
version 2 at https://gitlab.com/cryptsetup/LUKS2-docs.
cryptsetup January 2021 CRYPTSETUP(8)
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