x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
CRYPTSETUP-REENCRYPT(8) Maintenance Commands CRYPTSETUP-REENCRYPT(8)
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:
o device reencryption (reencrypt)
o device encryption (reencrypt --encrypt/--new/-N)
o 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
unlocked 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 guarantees 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 or cause out-of-memory conditions with unconditional process
termination. 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-blkid
Disable use of blkid library for checking and wiping on-disk
signatures.
--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/>.
cryptsetup 2.7.0 2024-08-30 CRYPTSETUP-REENCRYPT(8)
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