veritysetup(8) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | BASIC ACTIONS | OPTIONS | RETURN CODES | EXAMPLES | DM-VERITY ON-DISK SPECIFICATION | AUTHORS | REPORTING BUGS | SEE ALSO | CRYPTSETUP

VERITYSETUP(8)            Maintenance Commands            VERITYSETUP(8)

NAME         top

       veritysetup - manage dm-verity (block level verification) volumes

SYNOPSIS         top

       veritysetup <action> [<options>] <action args>

DESCRIPTION         top

       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.

BASIC ACTIONS         top

       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].

OPTIONS         top

       --no-superblock
           Create or use dm-verity without permanent on-disk superblock.

       --format=number
           Specifies the hash version type. Format type 0 is original
           Chrome OS version. Format type 1 is current version.

       --data-block-size=bytes
           Used block size for the data device. (Note kernel supports
           only page-size as maximum here.)

       --hash-block-size=bytes
           Used block size for the hash device. (Note kernel supports
           only page-size as maximum here.)

       --data-blocks=blocks
           Size of data device used in verification. If not specified,
           the whole device is used.

       --hash-offset=bytes
           Offset of hash area/superblock on hash_device. Value must be
           aligned to disk sector offset.

       --salt=hex string
           Salt used for format or verification. Format is a hexadecimal
           string.

       --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. *--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.

       --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.

       --hash=hash
           Hash algorithm for dm-verity. For default see --help option.

       --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).

       --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.

       --use-tasklets
           Try to use kernel tasklets in dm-verity driver for
           performance reasons. This option is available since Linux
           kernel version 6.0.

       --deferred
           Defers device removal in close command until the last user
           closes it.

       --cancel-deferred
           Removes a previously configured deferred device removal in
           close command.

       --verbose, -v
           Print more information on command execution.

       --debug
           Run in debug mode with full diagnostic logs. Debug output
           lines are always prefixed by #.

       --version, -V
           Show the program version.

       --batch-mode, -q
           Do not ask for confirmation.

       --usage
           Show short option help.

       --help, -?
           Show help text and default parameters.

RETURN CODES         top

       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.

EXAMPLES         top

       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.

DM-VERITY ON-DISK SPECIFICATION         top

       The on-disk format specification is available at DMVerity
       <https://gitlab.com/cryptsetup/cryptsetup/wikis/DMVerity> page.

AUTHORS         top

       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>.

REPORTING BUGS         top

       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.

SEE ALSO         top

       Cryptsetup FAQ
       <https://gitlab.com/cryptsetup/cryptsetup/wikis/FrequentlyAskedQuestions>

       cryptsetup(8), integritysetup(8) and veritysetup(8)

CRYPTSETUP         top

       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

veritysetup 2.6.1-git          2022-12-14                 VERITYSETUP(8)

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