phpman > man > veritysetup(8)

VERITYSETUP(8)                          Maintenance Commands                          VERITYSETUP(8)



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

SYNOPSIS
       veritysetup <options> <action> <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 de‐
       vices 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, --root-hash-file]

              If option --root-hash-file is used, the root hash is stored in hex-encoded text format
              in <path>.

       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]

              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 <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 <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 [--hash-offset]

OPTIONS
       --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  de‐
              vice, 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  avail‐
              able 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 op‐
              tional 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  roothash signature file used to verify the root hash (in kernel).  This fea‐
              ture 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
              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_de‐‐
       vice> <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.


REPORTING BUGS
       Report bugs, including ones in the documentation, on the  cryptsetup  mailing  list  at  <dm-
       crypt AT saout.de>  or in the 'Issues' section on LUKS website.  Please attach the output of the
       failed command with the --debug option added.

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>.

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

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



veritysetup                                 January 2021                              VERITYSETUP(8)