Provided by: cryptsetup-bin_2.2.2-3ubuntu2_amd64 bug

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
       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>

              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]

              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.

       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

       --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
              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  the
              kernel  is  restarted  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.

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

       --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).

       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 <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

       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

       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

       Copyright © 2012-2019 Red Hat, Inc.
       Copyright © 2012-2019 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/cryptsetup/wikis/DMVerity