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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | RETURN CODES | EXAMPLES | REPORTING BUGS | AUTHORS | COPYRIGHT | SEE ALSO | COLOPHON |
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.
WARNING: The cryptsetup-reencrypt program is not resistant to
hardware or kernel failures during reencryption (you can lose you
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 by 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, --debug,
--device-size, --hash, --iter-time, --use-random | --use-urandom,
--keep-key, --key-size, --key-file, --key-slot, --keyfile-offset,
--keyfile-size, --tries, --use-directio, --use-fsync, --verbose,
--write-log, --uuid]
To encrypt data on (not yet encrypted) device, use --new with
combination with --reduce-device-size.
To remove encryption from device, use --decrypt.
For detailed description of encryption and key file options see
cryptsetup(8) man page.
--verbose, -v
Print more information on command execution.
--debug
Run in debug mode with full diagnostic logs. Debug output
lines are always prefixed by '#'.
--cipher, -c <cipher-spec>
Set the cipher specification string.
--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.
--hash, -h <hash-spec>
Specifies the hash used in the LUKS key setup scheme and
volume key digest.
NOTE: if this parameter is not specified, default hash
algorithm is always used for new device header.
--iter-time, -i <milliseconds>
The number of milliseconds to spend with PBKDF2 passphrase
processing for the new LUKS header.
--use-random
--use-urandom
Define which kernel random number generator will be used to
create the volume key.
--key-file, -d name
Read the passphrase from file.
WARNING: --key-file option can be used only if there 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-slot, -S <0-7>
Specify which key slot is used.
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.
--keep-key
Do not change encryption key, just reencrypt the LUKS header
and keyslots.
This option can be combined only with --hash or --iter-time
options.
--tries, -T
Number of retries for invalid passphrase entry.
--block-size, -B value
Use re-encryption block size of <value> in MiB.
Values can be between 1 and 64 MiB.
--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.
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.
--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.
WARNING: This is destructive operation and cannot be reverted.
Use with extreme care - shrinked filesystems are usually
unrecoverable.
You cannot shrink device more than by 64 MiB (131072 sectors).
--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.
--decrypt
Remove encryption (decrypt already encrypted device and remove
LUKS header).
WARNING: This is destructive operation and cannot be reverted.
--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.
--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.
--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.
--batch-mode, -q
Suppresses all warnings and reencryption progress output.
--version
Show the program version.
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 © 2012-2017 Milan Broz
Copyright © 2012-2017 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 2017-07-05. 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 March 2017 CRYPTSETUP-REENCRYPT(8)