veritysetup(8) — Linux manual page


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

       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

              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, --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

              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.

       status <name>

              Reports status for the active verity mapping <name>.

       dump <hash_device>

              Reports parameters of verity device from on-disk stored

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

OPTIONS         top

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

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

              Create or use dm-verity without permanent on-disk superblock.

              Specifies the hash version type.  Format type 0 is original
              Chrome OS version. Format type 1 is current version.

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

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

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

              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

              Use the provided UUID for format command instead of generating
              new one.

              The UUID must be provided in standard UUID format, e.g.

       --ignore-corruption , --restart-on-corruption
              Defines what to do if data integrity problem is detected (data

              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 the kernel is restarted
              immediately.  (You have to provide way how to avoid restart

              WARNING: Use these options only for very specific cases.
              These options are available since Linux kernel version 4.1.

              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.

              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 algorithm for dm-verity. For default see --help option.

              Show the program version.

              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.

              Note: block sizes for data and hash devices must match. Also,
              if the verity data_device is encrypted the fec_device should
              be too.

              This is the offset, in bytes, from the start of the FEC device
              to the beginning of the encoding data.

              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

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

RETURN CODES         top

              Veritysetup returns 0 on success and a non-zero value on

              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

       veritysetup --data-blocks=256 --hash-offset=1052672 format <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 <> 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

       This version is based on verification code written by Mikulas Patocka
       <> and rewritten for libcryptsetup by Milan Broz

COPYRIGHT         top

       Copyright © 2012-2020 Red Hat, Inc.
       Copyright © 2012-2020 Milan Broz

       This is free software; see the source for copying conditions.  There
       is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A

SEE ALSO         top

       The project website at 

       The verity on-disk format specification available at 

COLOPHON         top

       This page is part of the Cryptsetup ((open-source disk encryption))
       project.  Information about the project can be found at 
       ⟨⟩.  If you have a bug report
       for this manual page, send it to  This page was
       obtained from the project's upstream Git repository
       ⟨⟩ on 2020-07-14.  (At
       that time, the date of the most recent commit that was found in the
       repository was 2020-07-12.)  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

veritysetup                     January 2019                  VERITYSETUP(8)

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