|
HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|
|
NAME | SYNOPSIS | DESCRIPTION | LUKS2 REENCRYPTION | LUKS1 REENCRYPTION | OPTIONS | EXAMPLES | REPORTING BUGS | SEE ALSO | CRYPTSETUP |
|
|
|
CRYPTSETUP-REENCRYPT(8) Maintenance Commands CRYPTSETUP-REENCRYPT(8)
cryptsetup-reencrypt - reencrypt LUKS encrypted volumes in-place
cryptsetup reencrypt [<options>] <device> or --active-name <name>
[<new_name>]
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].
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.
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).
--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.
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
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.
Cryptsetup FAQ
<https://gitlab.com/cryptsetup/cryptsetup/wikis/FrequentlyAskedQuestions>
cryptsetup(8), integritysetup(8) and veritysetup(8)
Part of cryptsetup project
<https://gitlab.com/cryptsetup/cryptsetup/>. This page is part of
the Cryptsetup ((open-source disk encryption)) project.
Information about the project can be found at
⟨https://gitlab.com/cryptsetup/cryptsetup⟩. If you have a bug
report for this manual page, send it to dm-crypt@saout.de. This
page was obtained from the project's upstream Git repository
⟨https://gitlab.com/cryptsetup/cryptsetup.git⟩ on 2023-12-22. (At
that time, the date of the most recent commit that was found in
the repository was 2023-12-20.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
cryptsetup 2.6.1-git 2022-12-14 CRYPTSETUP-REENCRYPT(8)
Pages that refer to this page: cryptsetup(8)
|
HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|