Steps to reproduce:

0. enter the CrOS chroot
1. ./build_image base
2. ./verify_rootfs_chksum.sh --image ../build/images/amd64-generic/latest/chromiumos_base_image.bin

The command immediately fails with this output:

missing value: create
Usage:
  /bin/verity <arg>=<value>...
Options:
  mode              One of 'create' or 'verify'
  alg               Hash algorithm to use. One of:
                      sha512 sha384 sha256 sha224 sha1 sha
                      mdc2 ripemd160 md5 md4 md2
  payload           Path to the image to hash
  payload_blocks    Size of the image, in blocks (4096 bytes)
  hashtree          Path to a hash tree to create or read from
  root_hexdigest    Digest of the root node (in hex) for verification
  salt              Salt (in hex)

ERROR   : Sat Jan 13 18:33:56 EST 2018
ERROR   :  PGID  PPID   PID     ELAPSED     TIME %CPU COMMAND
ERROR   : 29025     4 29025    01:42:12 00:00:00  0.0 -bash
ERROR   : 31137 29025 31137       00:12 00:00:00  0.3  \_ /bin/bash ./verify_rootfs_chksum.sh --image ../build/images/amd64-generic/latest/chromiumos_base_image.bin
ERROR   : 31137 31137 31284       00:05 00:00:00  0.0      \_ /bin/bash ./verify_rootfs_chksum.sh --image ../build/images/amd64-generic/latest/chromiumos_base_image.bin
ERROR   : 31137 31284 31285       00:05 00:00:00  0.0          \_ ps f -o pgid,ppid,pid,etime,cputime,%cpu,command
ERROR   : Arguments of 31137: ./verify_rootfs_chksum.sh '--image' '../build/images/amd64-generic/latest/chromiumos_base_image.bin'
ERROR   : Backtrace:  (most recent call is last)
ERROR   :  verify_rootfs_chksum.sh:94:main(), called: die_err_trap  
ERROR   : 
ERROR   : Command failed:
ERROR   :   Command 'table="vroot none ro,"$(sudo "${VERITY}" create 0         "${verity_algorithm}"         "${ROOTFS_IMG}"         $((rootfs_sectors / 8))         /dev/null)' exited with nonzero code: 255