man > veritysetup(8)

VERITYSETUP(8)                          Maintenance Commands                          VERITYSETUP(8)

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

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

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

AUTHORS
       The first implementation of veritysetup was written by Chrome OS authors.

       This version is based on verification code written by Mikulas Patocka <mpatocka AT redhat.com>
       and rewritten for libcryptsetup by Milan Broz <gmazyland AT gmail.com>.

REPORTING BUGS
       Report bugs at cryptsetup mailing list <cryptsetup AT lists.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
       Cryptsetup FAQ <https://gitlab.com/cryptsetup/cryptsetup/wikis/FrequentlyAskedQuestions>

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

CRYPTSETUP
       Part of cryptsetup project <https://gitlab.com/cryptsetup/cryptsetup/>.

veritysetup 2.7.0                            2024-11-14                               VERITYSETUP(8)