Provided by: systemd-cryptsetup_256.5-2ubuntu3_amd64 bug

NAME

       veritytab - Configuration for verity block devices

SYNOPSIS

       /etc/veritytab

DESCRIPTION

       The /etc/veritytab file describes verity protected block devices that are set up during
       system boot.

       Empty lines and lines starting with the "#" character are ignored. Each of the remaining
       lines describes one verity protected block device. Fields are delimited by white space.

       Each line is in the form

           volume-name data-device hash-device roothash [options]

       The first four fields are mandatory, the remaining one is optional.

       The first field contains the name of the resulting verity volume; its block device is set
       up below /dev/mapper/.

       The second field contains a path to the underlying block data device, or a specification
       of a block device via UUID= followed by the UUID.

       The third field contains a path to the underlying block hash device, or a specification of
       a block device via UUID= followed by the UUID.

       The fourth field is the roothash in hexadecimal.

       The fifth field, if present, is a comma-delimited list of options. The following options
       are recognized:

       superblock=BOOL
           Use dm-verity with or without permanent on-disk superblock.

           Added in version 254.

       format=NUMBER
           Specifies the hash version type. Format type "0" is original Chrome OS version. Format
           type "1" is modern version.

           Added in version 254.

       data-block-size=BYTES
           Used block size for the data device. (Note kernel supports only page-size as maximum
           here; Multiples of 512 bytes.)

           Added in version 254.

       hash-block-size=BYTES
           Used block size for the hash device. (Note kernel supports only page-size as maximum
           here; Multiples of 512 bytes.)

           Added in version 254.

       data-blocks=BLOCKS
           Number of blocks of data device used in verification. If not specified, the whole
           device is used.

           Added in version 254.

       hash-offset=BYTES
           Offset of hash area/superblock on "hash-device". (Multiples of 512 bytes.)

           Added in version 254.

       salt=HEX
           Salt used for format or verification. Format is a hexadecimal string; 256 bytes long
           maximum; "-" is the special value for empty.

           Added in version 254.

       uuid=UUID
           Use the provided UUID instead of generating new one. The UUID must be provided in
           standard UUID format, e.g.  "12345678-1234-1234-1234-123456789abc".

           Added in version 254.

       ignore-corruption, restart-on-corruption, panic-on-corruption
           Defines what to do if a data verity 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.)

           Added in version 248.

       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.
           Added in version 248.

       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.
           Added in version 248.

       hash=HASH
           Hash algorithm for dm-verity. This should be the name of the algorithm, like "sha1".
           For default see veritysetup --help.

           Added in version 254.

       fec-device=PATH
           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. 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.

           Added in version 254.

       fec-offset=BYTES
           This is the offset, in bytes, from the start of the FEC device to the beginning of the
           encoding data. (Aligned on 512 bytes.)

           Added in version 254.

       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).

           Added in version 254.

       root-hash-signature=PATH|base64:HEX
           A base64 string encoding the root hash signature prefixed by "base64:" or a path to
           roothash signature file used to verify the root hash (in kernel). This feature
           requires Linux kernel version 5.4 or more recent.

           Added in version 248.

       _netdev
           Marks this veritysetup device as requiring network. It will be started after the
           network is available, similarly to systemd.mount(5) units marked with _netdev. The
           service unit to set up this device will be ordered between remote-fs-pre.target and
           remote-veritysetup.target, instead of veritysetup-pre.target and veritysetup.target.

           Hint: if this device is used for a mount point that is specified in fstab(5), the
           _netdev option should also be used for the mount point. Otherwise, a dependency loop
           might be created where the mount point will be pulled in by local-fs.target, while the
           service to configure the network is usually only started after the local file system
           has been mounted.

           Added in version 248.

       noauto
           This device will not be added to veritysetup.target. This means that it will not be
           automatically enabled on boot, unless something else pulls it in. In particular, if
           the device is used for a mount point, it'll be enabled automatically during boot,
           unless the mount point itself is also disabled with noauto.

           Added in version 248.

       nofail
           This device will not be a hard dependency of veritysetup.target. It'll still be pulled
           in and started, but the system will not wait for the device to show up and be enabled,
           and boot will not fail if this is unsuccessful. Note that other units that depend on
           the enabled device may still fail. In particular, if the device is used for a mount
           point, the mount point itself also needs to have the nofail option, or the boot will
           fail if the device is not enabled successfully.

           Added in version 248.

       x-initrd.attach
           Setup this verity protected block device in the initrd, similarly to systemd.mount(5)
           units marked with x-initrd.mount.

           Although it's not necessary to mark the mount entry for the root file system with
           x-initrd.mount, x-initrd.attach is still recommended with the verity protected block
           device containing the root file system as otherwise systemd will attempt to detach the
           device during the regular system shutdown while it's still in use. With this option
           the device will still be detached but later after the root file system is unmounted.

           All other verity protected block devices that contain file systems mounted in the
           initrd should use this option.

           Added in version 248.

       At early boot and when the system manager configuration is reloaded, this file is
       translated into native systemd units by systemd-veritysetup-generator(8).

EXAMPLES

       Example 1. /etc/veritytab example

       Set up two verity protected block devices. One using device blocks, another using files.

           usr  PARTUUID=783e45ae-7aa3-484a-beef-a80ff9c19cbb PARTUUID=21dc1dfe-4c33-8b48-98a9-918a22eb3e37 36e3f740ad502e2c25e2a23d9c7c17bf0fdad2300b7580842d4b7ec1fb0fa263 auto
           data /etc/data /etc/hash a5ee4b42f70ae1f46a08a7c92c2e0a20672ad2f514792730f5d49d7606ab8fdf auto

SEE ALSO

       systemd(1), systemd-veritysetup@.service(8), systemd-veritysetup-generator(8), fstab(5),
       veritysetup(8)