veritysetup(8) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | RETURN CODES | EXAMPLES | REPORTING BUGS | AUTHORS | COPYRIGHT | SEE ALSO | COLOPHON

VERITYSETUP(8)            Maintenance Commands            VERITYSETUP(8)

NAME         top

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

SYNOPSIS         top

       veritysetup <options> <action> <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.

       Veritysetup supports these operations:

       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]

       open <data_device> <name> <hash_device> <root_hash>
       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]

              If option --no-superblock is used, you have to use as the
              same options as in initial format operation.

       verify <data_device> <hash_device> <root_hash>

              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.

              <options> can be [--hash-offset, --no-superblock]

              If option --no-superblock is used, you have to use as the
              same options as in initial format operation.

       close <name>

              Removes existing mapping <name>.

              For backward compatibility there is remove command alias
              for close command.

              <options> can be [--deferred] or [--cancel-deferred]

       status <name>

              Reports status for the active verity mapping <name>.

       dump <hash_device>

              Reports parameters of verity device from on-disk stored
              superblock.

              <options> can be [--no-superblock]

OPTIONS         top

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

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

       --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.

       --version
              Show the program version.

       --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-signature=FILE
              Path to roothash signature file used to verify the root
              hash (in kernel).  This feature requires Linux kernel
              version 5.4 or more recent.

       --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.

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 <data_device> <hash_device>

       Calculates and stores verification data on hash_device for the
       whole data_device.

       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 --fec-device=<fec_device> --fec-roots=10 format
       <data_device> <hash_device>

       Calculates and stores verification and encoding data for
       data_device.

REPORTING BUGS         top

       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.

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>.

COPYRIGHT         top

       Copyright © 2012-2021 Red Hat, Inc.
       Copyright © 2012-2021 Milan Broz

       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         top

       The project website at https://gitlab.com/cryptsetup/cryptsetup 

       The verity on-disk format specification available at
       https://gitlab.com/cryptsetup/cryptsetup/wikis/DMVerity 

COLOPHON         top

       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 2021-04-01.
       (At that time, the date of the most recent commit that was found
       in the repository was 2021-03-30.)  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                   January 2021                VERITYSETUP(8)

Pages that refer to this page: veritytab(5)systemd-veritysetup-generator(8)systemd-veritysetup@.service(8)