1VERITYSETUP(8) Maintenance Commands VERITYSETUP(8)
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6 veritysetup - manage dm-verity (block level verification) volumes
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9 veritysetup <action> [<options>] <action args>
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12 Veritysetup is used to configure dm-verity managed device-mapper
13 mappings.
14 Device-mapper verity target provides read-only transparent integrity
16 checking of block devices using kernel crypto API.
17 The dm-verity devices are always read-only.
19
21 Veritysetup supports these operations:
22 FORMAT
24 format <data_device> <hash_device>
25 Calculates and permanently stores hash verification data for
27 data_device. Hash area can be located on the same device after data if
28 specified by --hash-offset option.
29 Note you need to provide root hash string for device verification or
31 activation. Root hash must be trusted.
32 The data or hash device argument can be block device or file image. If
34 hash device path doesn’t exist, it will be created as file.
35 <options> can be [--hash, --no-superblock, --format, --data-block-size,
37 --hash-block-size, --data-blocks, --hash-offset, --salt, --uuid,
38 --root-hash-file].
39 If option --root-hash-file is used, the root hash is stored in
41 hex-encoded text format in <path>.
42 OPEN
44 open <data_device> <name> <hash_device> <root_hash>
45 open <data_device> <name> <hash_device> --root-hash-file <path>
46 create <name> <data_device> <hash_device> <root_hash> (OBSOLETE syntax)
47 Creates a mapping with <name> backed by device <data_device> and using
49 <hash_device> for in-kernel verification.
50 The <root_hash> is a hexadecimal string.
52 <options> can be [--hash-offset, --no-superblock, --ignore-corruption
54 or --restart-on-corruption, --panic-on-corruption,
55 --ignore-zero-blocks, --check-at-most-once, --root-hash-signature,
56 --root-hash-file].
57 If option --root-hash-file is used, the root hash is read from <path>
59 instead of from the command line parameter. Expects hex-encoded text,
60 without terminating newline.
61 If option --no-superblock is used, you have to use as the same options
63 as in initial format operation.
64 VERIFY
66 verify <data_device> <hash_device> <root_hash>
67 verify <data_device> <hash_device> --root-hash-file <path>
68 Verifies data on data_device with use of hash blocks stored on
70 hash_device.
71 This command performs userspace verification, no kernel device is
73 created.
74 The <root_hash> is a hexadecimal string.
76 If option --root-hash-file is used, the root hash is read from <path>
78 instead of from the command line parameter. Expects hex-encoded text,
79 without terminating newline.
80 <options> can be [--hash-offset, --no-superblock, --root-hash-file].
82 If option --no-superblock is used, you have to use as the same options
84 as in initial format operation.
85 CLOSE
87 close <name>
88 remove <name> (OBSOLETE syntax)
89 Removes existing mapping <name>.
91 <options> can be [--deferred] or [--cancel-deferred].
93 STATUS
95 status <name>
96 Reports status for the active verity mapping <name>.
98 DUMP
100 dump <hash_device>
101 Reports parameters of verity device from on-disk stored superblock.
103 <options> can be [--hash-offset].
105
107 --no-superblock
108 Create or use dm-verity without permanent on-disk superblock.
109 --format=number
111 Specifies the hash version type. Format type 0 is original Chrome
112 OS version. Format type 1 is current version.
113 --data-block-size=bytes
115 Used block size for the data device. (Note kernel supports only
116 page-size as maximum here.)
117 --hash-block-size=bytes
119 Used block size for the hash device. (Note kernel supports only
120 page-size as maximum here.)
121 --data-blocks=blocks
123 Size of data device used in verification. If not specified, the
124 whole device is used.
125 --hash-offset=bytes
127 Offset of hash area/superblock on hash_device. Value must be
128 aligned to disk sector offset.
129 --salt=hex string
131 Salt used for format or verification. Format is a hexadecimal
132 string.
133 --uuid=UUID
135 Use the provided UUID for format command instead of generating new
136 one.
137 The UUID must be provided in standard UUID format, e.g.
139 12345678-1234-1234-1234-123456789abc. *--ignore-corruption ,
140 --restart-on-corruption ,
141 --panic-on-corruption*
143 Defines what to do if data integrity problem is detected (data
144 corruption).
145 Without these options kernel fails the IO operation with I/O error.
147 With --ignore-corruption option the corruption is only logged. With
148 --restart-on-corruption or --panic-on-corruption the kernel is
149 restarted (panicked) immediately. (You have to provide way how to
150 avoid restart loops.)
151 WARNING: Use these options only for very specific cases. These
153 options are available since Linux kernel version 4.1.
154 --ignore-zero-blocks
156 Instruct kernel to not verify blocks that are expected to contain
157 zeroes and always directly return zeroes instead.
158 WARNING: Use this option only in very specific cases. This option
160 is available since Linux kernel version 4.5.
161 --check-at-most-once
163 Instruct kernel to verify blocks only the first time they are read
164 from the data device, rather than every time.
165 WARNING: It provides a reduced level of security because only
167 offline tampering of the data device’s content will be detected,
168 not online tampering. This option is available since Linux kernel
169 version 4.17.
170 --hash=hash
172 Hash algorithm for dm-verity. For default see --help option.
173 --fec-device=fec_device
175 Use forward error correction (FEC) to recover from corruption if
176 hash verification fails. Use encoding data from the specified
177 device.
178 The fec device argument can be block device or file image. For
180 format, if fec device path doesn’t exist, it will be created as
181 file.
182 Block sizes for data and hash devices must match. Also, if the
184 verity data_device is encrypted the fec_device should be too.
185 FEC calculation covers data, hash area, and optional foreign
187 metadata stored on the same device with the hash tree (additional
188 space after hash area). Size of this optional additional area
189 protected by FEC is calculated from image sizes, so you must be
190 sure that you use the same images for activation.
191 If the hash device is in a separate image, metadata covers the
193 whole rest of the image after the hash area.
194 If hash and FEC device is in the image, metadata ends on the FEC
196 area offset.
197 --fec-offset=bytes
199 This is the offset, in bytes, from the start of the FEC device to
200 the beginning of the encoding data.
201 --fec-roots=num
203 Number of generator roots. This equals to the number of parity
204 bytes in the encoding data. In RS(M, N) encoding, the number of
205 roots is M-N. M is 255 and M-N is between 2 and 24 (including).
206 --root-hash-file=FILE
208 Path to file with stored root hash in hex-encoded text.
209 --root-hash-signature=FILE
211 Path to root hash signature file used to verify the root hash (in
212 kernel). This feature requires Linux kernel version 5.4 or more
213 recent.
214 --deferred
216 Defers device removal in close command until the last user closes
217 it.
218 --cancel-deferred
220 Removes a previously configured deferred device removal in close
221 command.
222 --verbose, -v
224 Print more information on command execution.
225 --debug
227 Run in debug mode with full diagnostic logs. Debug output lines are
228 always prefixed by #.
229 --version, -V
231 Show the program version.
232 --batch-mode, -q
234 Do not ask for confirmation.
235 --usage
237 Show short option help.
238 --help, -?
240 Show help text and default parameters.
241
243 Veritysetup returns 0 on success and a non-zero value on error.
244 Error codes are: 1 wrong parameters, 2 no permission, 3 out of memory,
246 4 wrong device specified, 5 device already exists or device is busy.
247
249 veritysetup --data-blocks=256 format <data_device> <hash_device>
250 Calculates and stores verification data on hash_device for the first
252 256 blocks (of block-size). If hash_device does not exist, it is
253 created (as file image).
254 veritysetup format --root-hash-file <path> <data_device> <hash_device>
256 Calculates and stores verification data on hash_device for the whole
258 data_device, and store the root hash as hex-encoded text in <path>.
259 veritysetup --data-blocks=256 --hash-offset=1052672 format <device>
261 <device>
262 Verification data (hashes) is stored on the same device as data
264 (starting at hash-offset). Hash-offset must be greater than number of
265 blocks in data-area.
266 veritysetup --data-blocks=256 --hash-offset=1052672 create test-device
268 <device> <device> <root_hash>
269 Activates the verity device named test-device. Options --data-blocks
271 and --hash-offset are the same as in the format command. The
272 <root_hash> was calculated in format command.
273 veritysetup --data-blocks=256 --hash-offset=1052672 verify
275 <data_device> <hash_device> <root_hash>
276 Verifies device without activation (in userspace).
278 veritysetup --data-blocks=256 --hash-offset=1052672 --root-hash-file
280 <path> verify <data_device> <hash_device>
281 Verifies device without activation (in userspace). Root hash passed via
283 a file rather than inline.
284 veritysetup --fec-device=<fec_device> --fec-roots=10 format
286 <data_device> <hash_device>
287 Calculates and stores verification and encoding data for data_device.
289
291 The on-disk format specification is available at DMVerity
292 <https://gitlab.com/cryptsetup/cryptsetup/wikis/DMVerity> page.
293
295 The first implementation of veritysetup was written by Chrome OS
296 authors.
297 This version is based on verification code written by Mikulas Patocka
299 <mpatocka@redhat.com> and rewritten for libcryptsetup by Milan Broz
300 <gmazyland@gmail.com>.
301
303 Report bugs at cryptsetup mailing list <cryptsetup@lists.linux.dev> or
304 in Issues project section
305 <https://gitlab.com/cryptsetup/cryptsetup/-/issues/new>.
306 Please attach output of the failed command with --debug option added.
308
310 Cryptsetup FAQ
311 <https://gitlab.com/cryptsetup/cryptsetup/wikis/FrequentlyAskedQuestions>
312 cryptsetup(8), integritysetup(8) and veritysetup(8)
314
316 Part of cryptsetup project <https://gitlab.com/cryptsetup/cryptsetup/>.
317veritysetup 2.5.0 2022-07-28 VERITYSETUP(8)