NAME
cryptsetup-reencrypt - reencrypt LUKS encrypted volumes in-placeSYNOPSIS
cryptsetup reencrypt [<options>] <device> or --active-name <name> [<new_name>]DESCRIPTION
Run LUKS device reencryption.•device reencryption
(reencrypt)
•device encryption (reencrypt
--encrypt/--new/-N)
•device decryption (reencrypt
--decrypt)
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.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).OPTIONS
--block-size value (LUKS1 only)Use re-encryption block size of value
in MiB.
Values can be between 1 and 64 MiB.
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 call after every written block. This
applies for reencryption log files as well.
Update log file after every block write. This
can slow down reencryption but will minimize data loss in the case of system
crash.
Specifies required (encryption mode) or
expected (other modes) LUKS format. Accepts only luks1 or
luks2.
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).
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.
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.
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.
Skip value bytes at the beginning of
the key file.
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.
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.
Define which kernel random number generator
will be used to create the volume 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.
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.
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.
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.
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).
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).
The number of milliseconds to spend with PBKDF
passphrase processing for the new LUKS header.
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.
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.
Avoid PBKDF benchmark and set time cost
(iterations) directly. It can be used for LUKS/LUKS2 device only. See
--pbkdf option for more info.
Print separate line every seconds with
reencryption progress.
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):
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.
{ "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 }
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.
How often the input of the passphrase shall be
retried. The default is 3 tries.
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.
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.
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.
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.
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 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).
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.
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.
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.
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).
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).
This option can be used to set specific cipher
encryption for the LUKS2 keyslot area.
This option can be used to set specific key
size for the LUKS2 keyslot area.
Initialize (and run) device in-place
encryption mode.
Initialize (and run) device decryption
mode.
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 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.
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)
The hash algorithm used with
"--resilience checksum" only. The default hash is sha256. With other
resilience modes, the hash parameter is ignored.
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.
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).
Suppresses all confirmation questions. Use
with care!
If the --verify-passphrase option is not specified, this option also switches
off the passphrase verification.
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.
Show the program version.
Show short option 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):LUKS2 REENCRYPTION EXAMPLES
Reencrypt LUKS2 device (refresh volume key only):LUKS2 DECRYPTION EXAMPLES
Decrypt LUKS2 device with header put in head of data device (header file does not exist):REPORTING BUGS
Report bugs at cryptsetup <[email protected]>mailing or in Issues project section <https://gitlab.com/cryptsetup/cryptsetup/-/issues/new>.SEE ALSO
Cryptsetup FAQ <https://gitlab.com/cryptsetup/cryptsetup/wikis/FrequentlyAskedQuestions>CRYPTSETUP
Part of cryptsetup project <https://gitlab.com/cryptsetup/cryptsetup/>.2023-12-18 | cryptsetup 2.6.1 |