cryptsetup-reencrypt
CRYPTSETUP-REENCRYPT(8) Maintenance Commands CRYPTSETUP-REENCRYPT(8)
NAME
cryptsetup-reencrypt - tool for offline LUKS device re-encryption
SYNOPSIS
cryptsetup-reencrypt <options> <device>
DESCRIPTION
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 us-
ing ctrl+c) but you need to retain temporary files named
LUKS-<uuid>.[log|org|new]. LUKS device is unavailable until reencryp-
tion 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).
OPTIONS
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, --key-
file-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 crypt-
setup(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 cipher-
text and LUKS header on different devices.
WARNING: There is no check whether the ciphertext device speci-
fied 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 pro-
cessing 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 op-
tion.
--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 repre-
sents kilobytes). Note that it is maximal value, PBKDF bench-
mark 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 par-
tition (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 unrecov-
erable.
--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 re-
lated 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 reen-
cryption log files as well.
--use-random
--use-urandom
Define which kernel random number generator will be used to cre-
ate 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.
RETURN CODES
Cryptsetup-reencrypt returns 0 on success and a non-zero value on er-
ror.
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.
EXAMPLES
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
REPORTING BUGS
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 --de-
bug option added.
AUTHORS
Cryptsetup-reencrypt was written by Milan Broz <gmazyland@gmail.com>.
COPYRIGHT
Copyright (C) 2012-2019 Milan Broz
Copyright (C) 2012-2019 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.
SEE ALSO
The project website at https://gitlab.com/cryptsetup/cryptsetup
cryptsetup-reencrypt January 2019 CRYPTSETUP-REENCRYPT(8)
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