cryptsetup/man/veritysetup.8

.TH VERITYSETUP "8" "December 2013" "veritysetup" "Maintenance Commands"
.SH NAME
veritysetup - manage dm-verity (block level verification) volumes
.SH SYNOPSIS
.B veritysetup <options> <action> <action args>
.SH DESCRIPTION
.PP
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:
.PP
\fIformat\fR <data_device> <hash_device>
.IP
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.

\fB<options>\fR can be [\-\-hash, \-\-no-superblock, \-\-format,
\-\-data-block-size, \-\-hash-block-size, \-\-data-blocks, \-\-hash-offset,
\-\-salt, \-\-uuid]
.PP
\fIcreate\fR <name> <data_device> <hash_device> <root_hash>
.IP
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.

\fB<options>\fR can be [\-\-hash-offset, \-\-no-superblock,
\-\-ignore-corruption or \-\-restart-on-corruption, \-\-ignore-zero-blocks]

If option \-\-no-superblock is used, you have to use as the same options
as in initial format operation.
.PP
\fIverify\fR <data_device> <hash_device> <root_hash>
.IP
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.

\fB<options>\fR 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.
.PP
\fIremove\fR <name>
.IP
Removes existing mapping <name>.
.PP
\fIstatus\fR <name>
.IP
Reports status for the active verity mapping <name>.
.PP
\fIdump\fR <hash_device>
.IP
Reports parameters of verity device from on-disk stored superblock.

\fB<options>\fR can be [\-\-no-superblock]
.SH OPTIONS
.TP
.B "\-\-verbose, \-v"
Print more information on command execution.
.TP
.B "\-\-debug"
Run in debug mode with full diagnostic logs. Debug output
lines are always prefixed by '#'.
.TP
.B "\-\-no-superblock"
Create or use dm-verity without permanent on-disk superblock.
.TP
.B "\-\-format=number"
Specifies the hash version type.
Format type 0 is original Chrome OS version. Format type 1 is current version.
.TP
.B "\-\-data-block-size=bytes"
Used block size for the data device.
(Note kernel supports only page-size as maximum here.)
.TP
.B "\-\-hash-block-size=bytes"
Used block size for the hash device.
(Note kernel supports only page-size as maximum here.)
.TP
.B "\-\-data-blocks=blocks"
Size of data device used in verification.
If not specified, the whole device is used.
.TP
.B "\-\-hash-offset=bytes"
Offset of hash area/superblock on hash_device.
Value must be aligned to disk sector offset.
.TP
.B "\-\-salt=hex string"
Salt used for format or verification.
Format is a hexadecimal string.
.TP
.B "\-\-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.
.TP
.B "\-\-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 immediatelly.
(You have to provide way how to avoid restart loops.)

\fBWARNING:\fR Use these options only for very specific cases.
These options are available since Linux kernel version 4.1.
.TP
.B "\-\-ignore-zero-blocks"
Instruct kernel to not verify blocks that are expected to contain zeroes
and always directly return zeroes instead.

\fBWARNING:\fR Use this option only in very specific cases.
This option is available since Linux kernel version 4.5.
.TP
.B "\-\-version"
Show the program version.
.SH 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.
.SH 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.
.SH 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>.
.SH COPYRIGHT
Copyright \(co 2012-2016 Red Hat, Inc.
.br
Copyright \(co 2012-2016 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.
.SH SEE ALSO
The project website at \fBhttps://gitlab.com/cryptsetup/cryptsetup\fR

The verity on-disk format specification available at
\fBhttps://gitlab.com/cryptsetup/cryptsetup/wikis/DMVerity\fR