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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | RETURN CODES | EXAMPLES | REPORTING BUGS | AUTHORS | COPYRIGHT | SEE ALSO | COLOPHON |
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CRYPTSETUP-REENCRYPT(8) Maintenance Commands CRYPTSETUP-REENCRYPT(8)
cryptsetup-reencrypt - tool for offline LUKS device re-encryption
cryptsetup-reencrypt <options> <device>
Cryptsetup-reencrypt can be used to change reencryption
parameters which otherwise require full on-disk data change (re-
encryption).
You can regenerate volume key (the real key used in on-disk
encryption unclocked by passphrase), cipher, cipher mode.
Cryptsetup-reencrypt reencrypts data on LUKS device in-place.
During reencryption process the LUKS device is marked
unavailable.
NOTE: If you're looking for LUKS2 online reencryption manual
please read cryptsetup(8) man page instead (see reencrypt
action). This page is for legacy offline reencryption utility
only.
WARNING: The cryptsetup-reencrypt program is not resistant to
hardware or kernel failures during reencryption (you can lose
your data in this case).
ALWAYS BE SURE YOU HAVE RELIABLE BACKUP BEFORE USING THIS TOOL.
The reencryption can be temporarily suspended (by TERM signal or
by using ctrl+c) but you need to retain temporary files named
LUKS-<uuid>.[log|org|new]. LUKS device is unavailable until
reencryption is finished though.
Current working directory must be writable and temporary files
created during reencryption must be present.
For more info about LUKS see cryptsetup(8).
To start (or continue) re-encryption for <device> use:
cryptsetup-reencrypt <device>
<options> can be [--batch-mode, --block-size, --cipher | --keep-
key, --debug, --device-size, --hash, --header, --iter-time |
--pbkdf-force-iterations, --key-file, --key-size, --key-slot,
--keyfile-offset, --keyfile-size, --master-key-file, --tries,
--pbkdf, --pbkdf-memory, --pbkdf-parallel, --progress-frequency,
--use-directio, --use-random | --use-urandom, --use-fsync,
--uuid, --verbose, --write-log]
To encrypt data on (not yet encrypted) device, use --new in
combination with --reduce-device-size or with --header option for
detached header.
To remove encryption from device, use --decrypt.
For detailed description of encryption and key file options see
cryptsetup(8) man page.
--batch-mode, -q
Suppresses all warnings and reencryption progress output.
--block-size, -B value
Use re-encryption block size of <value> in MiB.
Values can be between 1 and 64 MiB.
--cipher, -c <cipher-spec>
Set the cipher specification string.
--debug
Run in debug mode with full diagnostic logs. Debug output
lines are always prefixed by '#'.
--decrypt
Remove encryption (decrypt already encrypted device and
remove LUKS header).
WARNING: This is destructive operation and cannot be
reverted.
--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.
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.
--hash, -h <hash-spec>
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.
NOTE: with LUKS2 format this option is only relevant when
new keyslot pbkdf algorithm is set to PBKDF2 (see
--pbkdf).
--header <LUKS header file>
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.
WARNING: There is no check whether the ciphertext device
specified actually belongs to the header given. If used
with --new option, the header file will created (or
overwritten). Use with care.
--iter-time, -i <milliseconds>
The number of milliseconds to spend with PBKDF2 passphrase
processing for the new LUKS header.
--keep-key
Do not change encryption key, just reencrypt the LUKS
header and keyslots.
This option can be combined only with --hash, --iter-time,
--pbkdf-force-iterations, --pbkdf (LUKS2 only),
--pbkdf-memory (Argon2i/id and LUKS2 only) and
--pbkdf-parallel (Argon2i/id and LUKS2 only) options.
--key-file, -d name
Read the passphrase from file.
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-reencrypt will ask
for all active keyslot passphrases.
--key-size, -s <bits>
Set 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.
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.
--key-slot, -S <0-MAX>
Specify which key slot is used. For LUKS1, max keyslot
number is 7. For LUKS2, it's 31.
WARNING: All other keyslots will be disabled if this
option is used.
--keyfile-offset value
Skip value bytes at the beginning of the key file.
--keyfile-size, -l
Read a maximum of value bytes from the key file. Default
is to read the whole file up to the compiled-in maximum.
--master-key-file
Use new volume (master) key stored in a file.
--new, -N
Create new header (encrypt not yet encrypted device).
This option must be used together with --reduce-device-
size.
WARNING: This is destructive operation and cannot be
reverted.
--pbkdf
Set Password-Based Key Derivation Function (PBKDF)
algorithm for LUKS keyslot. The PBKDF can be: pbkdf2,
argon2i for Argon2i or argon2id for Argon2id.
For LUKS1, only pbkdf2 is accepted (no need to use this
option).
--pbkdf-force-iterations <num>
Avoid PBKDF benchmark and set time cost (iterations)
directly.
--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.
--progress-frequency <seconds>
Print separate line every <seconds> with reencryption
progress.
--reduce-device-size size[units]
Enlarge data offset to specified value by shrinking device
size.
This means that last sectors on the original device will
be lost, ciphertext data will be effectively shifted by
specified number of sectors.
It can be useful if you e.g. added some space to
underlying partition (so last sectors contains no data).
For units suffix see --device-size parameter description.
You cannot shrink device more than by 64 MiB (131072
sectors).
WARNING: This is destructive operation and cannot be
reverted. Use with extreme care - shrunk filesystems are
usually unrecoverable.
--tries, -T
Number of retries for invalid passphrase entry.
--type <type>
Use only while encrypting not yet encrypted device (see
--new).
Specify LUKS version when performing in-place encryption.
If the parameter is omitted default value (LUKS1) is used.
Type may be one of: luks (default), luks1 or luks2.
--use-directio
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
Use fsync call after every written block. This applies for
reencryption log files as well.
--use-random
--use-urandom
Define which kernel random number generator will be used
to create the volume key.
--uuid <uuid>
Use only while resuming an interrupted decryption process
(see --decrypt).
To find out what <uuid> to pass look for temporary files
LUKS-<uuid>.[|log|org|new] of the interrupted decryption
process.
--verbose, -v
Print more information on command execution.
--version
Show the program version.
--write-log
Update log file after every block write. This can slow
down reencryption but will minimize data loss in the case
of system crash.
Cryptsetup-reencrypt returns 0 on success and a non-zero value on
error.
Error codes are: 1 wrong parameters, 2 no permission, 3 out of
memory, 4 wrong device specified, 5 device already exists or
device is busy.
Reencrypt /dev/sdb1 (change volume key)
cryptsetup-reencrypt /dev/sdb1
Reencrypt and also change cipher and cipher mode
cryptsetup-reencrypt /dev/sdb1 -c aes-xts-plain64
Add LUKS encryption to not yet encrypted device
First, be sure you have space added to disk.
Or alternatively shrink filesystem in advance.
Here we need 4096 512-bytes sectors (enough for 2x128 bit
key).
fdisk -u /dev/sdb # move sdb1 partition end + 4096 sectors
(or use resize2fs or tool for your filesystem and shrink
it)
cryptsetup-reencrypt /dev/sdb1 --new --reduce-device-size
4096S
Remove LUKS encryption completely
cryptsetup-reencrypt /dev/sdb1 --decrypt
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 --debug option added.
Cryptsetup-reencrypt was written by Milan Broz
<gmazyland@gmail.com>.
Copyright © 2012-2020 Milan Broz
Copyright © 2012-2020 Red Hat, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR
A PARTICULAR PURPOSE.
The project website at 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 2020-12-18.
(At that time, the date of the most recent commit that was found
in the repository was 2020-12-02.) 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-reencrypt January 2019 CRYPTSETUP-REENCRYPT(8)
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