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HTML rendering created 2024-06-26 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. |
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NAME | SYNOPSIS | DESCRIPTION | BASIC ACTIONS | OPTIONS | RETURN CODES | EXAMPLES | DM-VERITY ON-DISK SPECIFICATION | AUTHORS | REPORTING BUGS | SEE ALSO | CRYPTSETUP |
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VERITYSETUP(8) Maintenance Commands VERITYSETUP(8)
veritysetup - manage dm-verity (block level verification) volumes
veritysetup <action> [<options>] <action args>
Veritysetup is used to configure dm-verity managed device-mapper
mappings.
Device-mapper verity target provides read-only transparent
integrity checking of block devices using kernel crypto API.
The dm-verity devices are always read-only.
Veritysetup supports these operations:
FORMAT
format <data_device> <hash_device>
Calculates and permanently stores hash verification data for
data_device. Hash area can be located on the same device after
data if specified by --hash-offset option.
Note you need to provide root hash string for device verification
or activation. Root hash must be trusted.
The data or hash device argument can be block device or file
image. If hash device path doesn’t exist, it will be created as
file.
<options> can be [--hash, --no-superblock, --format,
--data-block-size, --hash-block-size, --data-blocks,
--hash-offset, --salt, --uuid, --root-hash-file].
If option --root-hash-file is used, the root hash is stored in
hex-encoded text format in <path>.
OPEN
open <data_device> <name> <hash_device> <root_hash>
open <data_device> <name> <hash_device> --root-hash-file <path>
create <name> <data_device> <hash_device> <root_hash> (OBSOLETE
syntax)
Creates a mapping with <name> backed by device <data_device> and
using <hash_device> for in-kernel verification.
The <root_hash> is a hexadecimal string.
<options> can be [--hash-offset, --no-superblock,
--ignore-corruption or --restart-on-corruption,
--panic-on-corruption, --ignore-zero-blocks,
--check-at-most-once, --root-hash-signature, --root-hash-file,
--use-tasklets].
If option --root-hash-file is used, the root hash is read from
<path> instead of from the command line parameter. Expects
hex-encoded text, without terminating newline.
If option --no-superblock is used, you have to use as the same
options as in initial format operation.
VERIFY
verify <data_device> <hash_device> <root_hash>
verify <data_device> <hash_device> --root-hash-file <path>
Verifies data on data_device with use of hash blocks stored on
hash_device.
This command performs userspace verification, no kernel device is
created.
The <root_hash> is a hexadecimal string.
If option --root-hash-file is used, the root hash is read from
<path> instead of from the command line parameter. Expects
hex-encoded text, without terminating newline.
<options> can be [--hash-offset, --no-superblock,
--root-hash-file].
If option --no-superblock is used, you have to use as the same
options as in initial format operation.
CLOSE
close <name>
remove <name> (OBSOLETE syntax)
Removes existing mapping <name>.
<options> can be [--deferred] or [--cancel-deferred].
STATUS
status <name>
Reports status for the active verity mapping <name>.
DUMP
dump <hash_device>
Reports parameters of verity device from on-disk stored
superblock.
<options> can be [--hash-offset].
--batch-mode, -q
Do not ask for confirmation.
--cancel-deferred
Removes a previously configured deferred device removal in
close command.
--check-at-most-once
Instruct kernel to verify blocks only the first time they are
read from the data device, rather than every time.
WARNING: It provides a reduced level of security because only
offline tampering of the data device’s content will be
detected, not online tampering. This option is available
since Linux kernel version 4.17.
--data-blocks=blocks
Size of data device used in verification. If not specified,
the whole device is used.
--data-block-size=bytes
Used block size for the data device. (Note kernel supports
only page-size as maximum here.)
--debug
Run in debug mode with full diagnostic logs. Debug output
lines are always prefixed by #.
--deferred
Defers device removal in close command until the last user
closes it.
--fec-device=fec_device
Use forward error correction (FEC) to recover from corruption
if hash verification fails. Use encoding data from the
specified device.
The fec device argument can be block device or file image.
For format, if fec device path doesn’t exist, it will be
created as file.
Block sizes for data and hash devices must match. Also, if
the verity data_device is encrypted the fec_device should be
too.
FEC calculation covers data, hash area, and optional foreign
metadata stored on the same device with the hash tree
(additional space after hash area). Size of this optional
additional area protected by FEC is calculated from image
sizes, so you must be sure that you use the same images for
activation.
If the hash device is in a separate image, metadata covers
the whole rest of the image after the hash area.
If hash and FEC device is in the image, metadata ends on the
FEC area offset.
--fec-offset=bytes
This is the offset, in bytes, from the start of the FEC
device to the beginning of the encoding data.
--fec-roots=num
Number of generator roots. This equals to the number of
parity bytes in the encoding data. In RS(M, N) encoding, the
number of roots is M-N. M is 255 and M-N is between 2 and 24
(including).
--format=number
Specifies the hash version type. Format type 0 is original
Chrome OS version. Format type 1 is current version.
--hash=hash
Hash algorithm for dm-verity. For default see --help option.
--hash-block-size=bytes
Used block size for the hash device. (Note kernel supports
only page-size as maximum here.)
--hash-offset=bytes
Offset of hash area/superblock on hash_device. Value must be
aligned to disk sector offset.
--help, -?
Show help text and default parameters.
--ignore-corruption, --restart-on-corruption,
--panic-on-corruption
Defines what to do if data integrity problem is detected
(data corruption).
Without these options kernel fails the IO operation with I/O
error. With --ignore-corruption option the corruption is only
logged. With --restart-on-corruption or --panic-on-corruption
the kernel is restarted (panicked) immediately. (You have to
provide way how to avoid restart loops.)
WARNING: Use these options only for very specific cases.
These options are available since Linux kernel version 4.1.
--ignore-zero-blocks
Instruct kernel to not verify blocks that are expected to
contain zeroes and always directly return zeroes instead.
WARNING: Use this option only in very specific cases. This
option is available since Linux kernel version 4.5.
--no-superblock
Create or use dm-verity without permanent on-disk superblock.
--root-hash-file=FILE
Path to file with stored root hash in hex-encoded text.
--root-hash-signature=FILE
Path to root hash signature file used to verify the root hash
(in kernel). This feature requires Linux kernel version 5.4
or more recent.
--salt=hex string
Salt used for format or verification. Format is a hexadecimal
string.
--usage
Show short option help.
--use-tasklets
Try to use kernel tasklets in dm-verity driver for
performance reasons. This option is available since Linux
kernel version 6.0.
--uuid=UUID
Use the provided UUID for format command instead of
generating new one.
The UUID must be provided in standard UUID format, e.g.
12345678-1234-1234-1234-123456789abc.
--verbose, -v
Print more information on command execution.
--version, -V
Show the program version.
Veritysetup 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.
veritysetup --data-blocks=256 format <data_device> <hash_device>
Calculates and stores verification data on hash_device for the
first 256 blocks (of block-size). If hash_device does not exist,
it is created (as file image).
veritysetup format --root-hash-file <path> <data_device>
<hash_device>
Calculates and stores verification data on hash_device for the
whole data_device, and store the root hash as hex-encoded text in
<path>.
veritysetup --data-blocks=256 --hash-offset=1052672 format
<device> <device>
Verification data (hashes) is stored on the same device as data
(starting at hash-offset). Hash-offset must be greater than
number of blocks in data-area.
veritysetup --data-blocks=256 --hash-offset=1052672 create
test-device <device> <device> <root_hash>
Activates the verity device named test-device. Options
--data-blocks and --hash-offset are the same as in the format
command. The <root_hash> was calculated in format command.
veritysetup --data-blocks=256 --hash-offset=1052672 verify
<data_device> <hash_device> <root_hash>
Verifies device without activation (in userspace).
veritysetup --data-blocks=256 --hash-offset=1052672
--root-hash-file <path> verify <data_device> <hash_device>
Verifies device without activation (in userspace). Root hash
passed via a file rather than inline.
veritysetup --fec-device=<fec_device> --fec-roots=10 format
<data_device> <hash_device>
Calculates and stores verification and encoding data for
data_device.
The on-disk format specification is available at DMVerity
<https://gitlab.com/cryptsetup/cryptsetup/wikis/DMVerity> page.
The first implementation of veritysetup was written by Chrome OS
authors.
This version is based on verification code written by Mikulas
Patocka <mpatocka@redhat.com> and rewritten for libcryptsetup by
Milan Broz <gmazyland@gmail.com>.
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 2024-06-14. (At
that time, the date of the most recent commit that was found in
the repository was 2024-06-11.) 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
veritysetup 2.8.0-git 2024-06-07 VERITYSETUP(8)
Pages that refer to this page: veritytab(5), cryptsetup(8), cryptsetup-benchmark(8), cryptsetup-bitlkDump(8), cryptsetup-close(8), cryptsetup-config(8), cryptsetup-convert(8), cryptsetup-erase(8), cryptsetup-fvault2Dump(8), cryptsetup-isLuks(8), cryptsetup-luksAddKey(8), cryptsetup-luksChangeKey(8), cryptsetup-luksConvertKey(8), cryptsetup-luksDump(8), cryptsetup-luksFormat(8), cryptsetup-luksHeaderBackup(8), cryptsetup-luksHeaderRestore(8), cryptsetup-luksKillSlot(8), cryptsetup-luksRemoveKey(8), cryptsetup-luksResume(8), cryptsetup-luksSuspend(8), cryptsetup-luksUUID(8), cryptsetup-open(8), cryptsetup-reencrypt(8), cryptsetup-refresh(8), cryptsetup-repair(8), cryptsetup-resize(8), cryptsetup-ssh(8), cryptsetup-status(8), cryptsetup-tcryptDump(8), cryptsetup-token(8), integritysetup(8), systemd-veritysetup-generator(8), systemd-veritysetup@.service(8), veritysetup(8)
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HTML rendering created 2024-06-26 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. |
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