Provided by: cryptsetup-bin_2.6.1-1ubuntu1_amd64 
NAME
cryptsetup-reencrypt - reencrypt LUKS encrypted volumes in-place
SYNOPSIS
cryptsetup reencrypt [<options>] <device> or --active-name <name> [<new_name>]
DESCRIPTION
Run LUKS device reencryption.
There are 3 basic modes of operation:
• device reencryption (reencrypt)
• device encryption (reencrypt --encrypt/--new/-N)
• device decryption (reencrypt --decrypt)
<device> or --active-name <name> (LUKS2 only) is mandatory parameter.
Cryptsetup reencrypt action can be used to change reencryption parameters which otherwise
require full on-disk data change (re-encryption). The reencrypt action reencrypts data on
LUKS device in-place.
You can regenerate volume key (the real key used in on-disk encryption unclocked by
passphrase), cipher, cipher mode or encryption sector size (LUKS2 only).
Reencryption process may be safely interrupted by a user via SIGINT signal (ctrl+c). Same
applies to SIGTERM signal (i.e. issued by systemd during system shutdown).
For in-place encryption mode, the reencrypt action additionally takes all options
available for luksFormat action for respective LUKS version (see cryptsetup-luksFormat man
page for more details). See cryptsetup-luksFormat(8).
NOTE that for encrypt and decrypt mode, the whole device must be treated as unencrypted —
there are no quarantees of confidentiality as part of the device contains plaintext.
ALWAYS BE SURE YOU HAVE RELIABLE BACKUP BEFORE USING THIS ACTION ON LUKS DEVICE.
<options> can be [--batch-mode, --block-size, --cipher, --debug, --debug-json, --decrypt,
--device-size, --disable-locks, --encrypt, --force-offline-reencrypt, --hash, --header,
--hotzone-size, --iter-time, --init-only, --keep-key, --key-file, --key-size, --key-slot,
--keyfile-offset, --keyfile-size, --tries, --timeout, --pbkdf, --pbkdf-force-iterations,
--pbkdf-memory, --pbkdf-parallel, --progress-frequency, --progress-json,
--reduce-device-size, --resilience, --resilience-hash, --resume-only, --sector-size,
--use-directio, --use-random, --use-urandom, --use-fsync, --uuid, --verbose,
--volume-key-file, --write-log].
LUKS2 REENCRYPTION
With <device> parameter cryptsetup looks up active <device> dm mapping. If no active
mapping is detected, it starts offline LUKS2 reencryption otherwise online reencryption
takes place.
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: either encrypt mode with --reduce-device-size option or decrypt mode with
original LUKS2 header exported in --header file.
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 or explicitly by user (action repair).
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.
LUKS1 REENCRYPTION
Current working directory must be writable and temporary files created during reencryption
must be present. During reencryption process the LUKS1 device is marked unavailable and
must be offline (no dm-crypt mapping or mounted filesystem).
WARNING: The LUKS1 reencryption code is not resistant to hardware or kernel failures
during reencryption (you can lose your data in this case).
OPTIONS
--block-size value (LUKS1 only)
Use re-encryption block size of value in MiB.
Values can be between 1 and 64 MiB.
--use-directio (LUKS1 only)
Use direct-io (O_DIRECT) for all read/write data operations related to block device
undergoing reencryption.
Useful if direct-io operations perform better than normal buffered operations (e.g. in
virtual environments).
--use-fsync (LUKS1 only)
Use fsync call after every written block. This applies for reencryption log files as
well.
--write-log (LUKS1 only)
Update log file after every block write. This can slow down reencryption but will
minimize data loss in the case of system crash.
--type <device-type>
Specifies required (encryption mode) or expected (other modes) LUKS format. Accepts
only luks1 or luks2.
--hash, -h <hash-spec>
LUKS1: Specifies the hash used in the LUKS1 key setup scheme and volume key digest.
NOTE: if this parameter is not specified, default hash algorithm is always used for
new LUKS1 device header.
LUKS2: Ignored unless new keyslot pbkdf algorithm is set to PBKDF2 (see --pbkdf).
--cipher, -c <cipher-spec>
LUKS2: Set the cipher specification string for data segment only.
LUKS1: Set the cipher specification string for data segment and keyslots.
NOTE: In encrypt mode, if cipher specification is omitted the default cipher is
applied. In reencrypt mode, if no new cipher specification is requested, the existing
cipher will remain in use. Unless the existing cipher was "cipher_null". In that case
default cipher would be applied as in encrypt mode.
cryptsetup --help shows the compiled-in defaults.
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.
--verify-passphrase, -y
When interactively asking for a passphrase, ask for it twice and complain if both
inputs do not match. 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.
WARNING: --key-file option can be used only if there is only one active keyslot, or
alternatively, also if --key-slot option is specified (then all other keyslots will be
disabled in new LUKS device).
If this option is not used, cryptsetup will ask for all active keyslot passphrases.
--keyfile-offset value
Skip value bytes at the beginning of the key file.
--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.
--volume-key-file, --master-key-file (OBSOLETE alias)
Use (set) new volume key stored in a file.
WARNING: If you create your own volume key, you need to make sure to do it right.
Otherwise, you can end up with a low-entropy or otherwise partially predictable volume
key which will compromise security.
--use-random, --use-urandom
Define which kernel random number generator will be used to create the volume key.
--keep-key
LUKS2: Do not change effective volume key and change other parameters provided it is
requested.
LUKS1: Reencrypt only the LUKS1 header and keyslots. Skips data in-place reencryption.
--key-slot, -S <0-N>
For LUKS operations that add key material, this option allows you to specify which key
slot is selected for the new key.
For reencryption mode it selects specific keyslot (and passphrase) that can be used to
unlock new volume key. If used all other keyslots get removed after reencryption
operation is finished.
The maximum number of key slots depends on the 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.
LUKS1: If you are increasing key size, there must be enough space in the LUKS header
for enlarged keyslots (data offset must be large enough) or reencryption cannot be
performed.
If there is not enough space for keyslots with new key size, you can destructively
shrink device with --reduce-device-size option.
--offset, -o <number of 512 byte sectors>
Start offset in the backend device in 512-byte sectors. This option is only relevant
for the encrypt mode.
The --offset option sets the data offset (payload) of data device and must be aligned
to 4096-byte sectors (must be multiple of 8). This option cannot be combined with
--align-payload option.
--device-size size[units]
Instead of real device size, use specified value. It means that only specified area
(from the start of the device to the specified size) will be reencrypted.
WARNING: This is destructive operation. Data beyond --device-size limit may be lost
after operation gets finished.
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).
--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 Argon2 <https://www.cryptolux.org/index.php/Argon2> for
more info).
For LUKS1, only PBKDF2 is accepted (no need to use this option). The default PBKDF 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 and is checked
against available CPU cores.
You can see all PBKDF parameters for particular LUKS2 keyslot with
cryptsetup-luksDump(8) 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.
MINIMAL AND MAXIMAL PBKDF COSTS: For PBKDF2, the minimum iteration 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 addressable memory on some CPU platforms.)
If the memory cost parameter is benchmarked (not specified by a parameter) 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 available, otherwise it is decreased).
--iter-time, -i <number of milliseconds>
The number of milliseconds to spend with PBKDF passphrase processing for the new LUKS
header.
--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.
--progress-frequency seconds
Print separate line every seconds with reencryption progress.
--progress-json
Prints progress data in JSON format suitable mostly for machine processing. It prints
separate line every half second (or based on --progress-frequency value). The JSON
output looks as follows during progress (except it’s compact single line):
{
"device":"/dev/sda" // backing device or file
"device_bytes":"8192", // bytes of I/O so far
"device_size":"44040192", // total bytes of I/O to go
"speed":"126877696", // calculated speed in bytes per second (based on progress so far)
"eta_ms":"2520012" // estimated time to finish an operation in milliseconds
"time_ms":"5561235" // total time spent in IO operation in milliseconds
}
Note on numbers in JSON output: Due to JSON parsers limitations all numbers are
represented in a string format due to need of full 64bit unsigned integers.
--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. 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. The default is 3 tries.
--align-payload <number of 512 byte sectors>
Align payload at a boundary of value 512-byte sectors.
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>
When used in encryption mode use the provided UUID for the new LUKS header instead of
generating a new one.
LUKS1 (only in decryption mode): To find out what UUID to pass look for temporary
files LUKS-UUID.[|log|org|new] of the interrupted decryption process.
The UUID must be provided in the standard UUID format, e.g.
12345678-1234-1234-1234-123456789abc.
--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.
If used with --encrypt/--new option, the header file will be created (or overwritten).
Use with care.
LUKS2: For decryption mode the option may be used to export original LUKS2 header to a
detached file. The passed future file must not exist at the time of initializing the
decryption operation. This frees space in head of data device so that data can be
moved at original LUKS2 header location. Later on decryption operation continues as if
the ordinary detached header was passed.
WARNING: Never put exported header file in a filesystem on top of device you are about
to decrypt! It would cause a deadlock.
--force-offline-reencrypt (LUKS2 only)
Bypass active device auto-detection and enforce offline reencryption.
This option is useful especially for reencryption of LUKS2 images put in files
(auto-detection is not reliable in this scenario).
It may also help in case active device auto-detection on particular data device does
not work or report errors.
WARNING: Use with extreme caution! This may destroy data if the device is activated
and/or actively used.
--force-password
Do not use password quality checking for new LUKS passwords.
This option 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).
--disable-locks
Disable lock protection for metadata on disk. This option is valid only for LUKS2 and
ignored for other formats.
NOTE: With locking disabled LUKS2 images in files can be fully (re)encrypted offline
without need for super user privileges provided used block ciphers are available in
crypto backend.
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 type.
--sector-size bytes (LUKS2 only)
Reencrypt device with new encryption sector size enforced.
WARNING: Increasing encryption sector size may break hosted filesystem. Do not run
reencryption with --force-offline-reencrypt if unsure what block size was filesystem
formatted with.
--label <LABEL> --subsystem <SUBSYSTEM>
Set label and subsystem description for LUKS2 device. The label and subsystem are
optional fields and can be later used in udev scripts for triggering user actions once
the device marked by these labels is detected.
--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.
--encrypt, --new, -N
Initialize (and run) device in-place encryption mode.
--decrypt
Initialize (and run) device decryption mode.
--init-only (LUKS2 only)
Initialize reencryption (any mode) 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 (LUKS2 only)
Resume reencryption (any mode) 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 (LUKS2 only)
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 offline reencryption utility.
Resilience modes can be changed unless datashift mode is used for operation
initialization (encryption with --reduce-device-size option)
--resilience-hash hash (LUKS2 only)
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 (LUKS2 only)
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).
With decryption mode for devices with LUKS2 header placed in head of data device, the
option specifies how large is the first data segment moved from original data offset
pointer.
--reduce-device-size size
This means that last size sectors on the original device will be lost, data will be
effectively shifted by specified number of sectors.
It could be useful if you added some space to underlying partition or logical volume
(so last size sectors contains no data).
For units suffix see --device-size parameter description.
WARNING: This is a destructive operation and cannot be reverted. Use with extreme care
- accidentally overwritten filesystems are usually unrecoverable.
LUKS2: Initialize LUKS2 reencryption with data device size reduction (currently only
encryption mode is supported).
Recommended minimal size is twice the default LUKS2 header size (--reduce-device-size
32M) for encryption mode.
LUKS1: Enlarge data offset to specified value by shrinking device size.
You cannot shrink device more than by 64 MiB (131072 sectors).
--batch-mode, -q
Suppresses all confirmation questions. Use with care!
If the --verify-passphrase option is not specified, this option also switches off the
passphrase verification.
--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.
--version, -V
Show the program version.
--usage
Show short option help.
--help, -?
Show help text and default parameters.
EXAMPLES
NOTE: You may drop --type luks2 option as long as LUKS2 format is default.
LUKS2 ENCRYPTION EXAMPLES
Encrypt LUKS2 device (in-place). Make sure last 32 MiB on /dev/plaintext is unused (e.g.:
does not contain filesystem data):
cryptsetup reencrypt --encrypt --type luks2 --reduce-device-size 32m /dev/plaintext_device
Encrypt LUKS2 device (in-place) with detached header put in a file:
cryptsetup reencrypt --encrypt --type luks2 --header my_luks2_header /dev/plaintext_device
Initialize LUKS2 in-place encryption operation only and activate the device (not yet
encrypted):
cryptsetup reencrypt --encrypt --type luks2 --init-only --reduce-device-size 32m
/dev/plaintext_device my_future_luks_device
Resume online encryption on device initialized in example above:
cryptsetup reencrypt --resume-only /dev/plaintext_device or cryptsetup reencrypt
--active-name my_future_luks_device
LUKS2 REENCRYPTION EXAMPLES
Reencrypt LUKS2 device (refresh volume key only):
cryptsetup reencrypt /dev/encrypted_device
LUKS2 DECRYPTION EXAMPLES
Decrypt LUKS2 device with header put in head of data device (header file does not exist):
cryptsetup reencrypt --decrypt --header /export/header/to/file /dev/encrypted_device
Decrypt LUKS2 device with detached header (header file exists):
cryptsetup reencrypt --decrypt --header detached-luks2-header /dev/encrypted_device
Resume interrupted LUKS2 decryption:
cryptsetup reencrypt --resume-only --header luks2-hdr-file /dev/encrypted_device
REPORTING BUGS
Report bugs at cryptsetup mailing list <cryptsetup@lists.linux.dev> or in Issues project
section <https://gitlab.com/cryptsetup/cryptsetup/-/issues/new>.
Please attach output of the failed command with --debug option added.
SEE ALSO
Cryptsetup FAQ <https://gitlab.com/cryptsetup/cryptsetup/wikis/FrequentlyAskedQuestions>
cryptsetup(8), integritysetup(8) and veritysetup(8)
CRYPTSETUP
Part of cryptsetup project <https://gitlab.com/cryptsetup/cryptsetup/>.