summaryrefslogtreecommitdiffstats
path: root/man/systemd-dissect.xml
blob: b65a2c39f1d25fc2ed605b2abd588d16edafb536 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->

<refentry id="systemd-dissect" conditional='HAVE_BLKID'
    xmlns:xi="http://www.w3.org/2001/XInclude">

  <refentryinfo>
    <title>systemd-dissect</title>
    <productname>systemd</productname>
  </refentryinfo>

  <refmeta>
    <refentrytitle>systemd-dissect</refentrytitle>
    <manvolnum>1</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>systemd-dissect</refname>
    <refname>mount.ddi</refname>
    <refpurpose>Dissect Discoverable Disk Images (DDIs)</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <cmdsynopsis>
      <command>systemd-dissect</command> <arg choice="opt" rep="repeat">OPTIONS</arg> <arg choice="plain"><replaceable>IMAGE</replaceable></arg>
    </cmdsynopsis>
    <cmdsynopsis>
      <command>systemd-dissect</command> <arg choice="opt" rep="repeat">OPTIONS</arg> <arg>--mount</arg> <arg choice="plain"><replaceable>IMAGE</replaceable></arg> <arg choice="plain"><replaceable>PATH</replaceable></arg>
    </cmdsynopsis>
    <cmdsynopsis>
      <command>systemd-dissect</command> <arg choice="opt" rep="repeat">OPTIONS</arg> <arg>--umount</arg> <arg choice="plain"><replaceable>PATH</replaceable></arg>
    </cmdsynopsis>
    <cmdsynopsis>
      <command>systemd-dissect</command> <arg choice="opt" rep="repeat">OPTIONS</arg> <arg>--attach</arg> <arg choice="plain"><replaceable>IMAGE</replaceable></arg>
    </cmdsynopsis>
    <cmdsynopsis>
      <command>systemd-dissect</command> <arg choice="opt" rep="repeat">OPTIONS</arg> <arg>--detach</arg> <arg choice="plain"><replaceable>PATH</replaceable></arg>
    </cmdsynopsis>
    <cmdsynopsis>
      <command>systemd-dissect</command> <arg choice="opt" rep="repeat">OPTIONS</arg> <arg>--list</arg> <arg choice="plain"><replaceable>IMAGE</replaceable></arg>
    </cmdsynopsis>
    <cmdsynopsis>
      <command>systemd-dissect</command> <arg choice="opt" rep="repeat">OPTIONS</arg> <arg>--mtree</arg> <arg choice="plain"><replaceable>IMAGE</replaceable></arg>
    </cmdsynopsis>
    <cmdsynopsis>
      <command>systemd-dissect</command> <arg choice="opt" rep="repeat">OPTIONS</arg> <arg>--with</arg> <arg choice="plain"><replaceable>IMAGE</replaceable></arg> <arg choice="opt" rep="repeat"><replaceable>COMMAND</replaceable></arg>
    </cmdsynopsis>
    <cmdsynopsis>
      <command>systemd-dissect</command> <arg choice="opt" rep="repeat">OPTIONS</arg> <arg>--copy-from</arg> <arg choice="plain"><replaceable>IMAGE</replaceable></arg> <arg choice="plain"><replaceable>PATH</replaceable></arg> <arg choice="opt"><replaceable>TARGET</replaceable></arg>
    </cmdsynopsis>
    <cmdsynopsis>
      <command>systemd-dissect</command> <arg choice="opt" rep="repeat">OPTIONS</arg> <arg>--copy-to</arg> <arg choice="plain"><replaceable>IMAGE</replaceable></arg> <arg choice="opt"><replaceable>SOURCE</replaceable></arg> <arg choice="plain"><replaceable>PATH</replaceable></arg>
    </cmdsynopsis>
    <cmdsynopsis>
      <command>systemd-dissect</command> <arg choice="opt" rep="repeat">OPTIONS</arg> <arg>--make-archive</arg> <arg choice="plain"><replaceable>IMAGE</replaceable></arg> <arg choice="opt"><replaceable>TARGET</replaceable></arg>
    </cmdsynopsis>
    <cmdsynopsis>
      <command>systemd-dissect</command> <arg choice="opt" rep="repeat">OPTIONS</arg> <arg>--discover</arg>
    </cmdsynopsis>
    <cmdsynopsis>
      <command>systemd-dissect</command> <arg choice="opt" rep="repeat">OPTIONS</arg> <arg>--validate</arg> <arg choice="plain"><replaceable>IMAGE</replaceable></arg>
    </cmdsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><command>systemd-dissect</command> is a tool for introspecting and interacting with file system OS
    disk images, specifically Discoverable Disk Images (DDIs). It supports four different operations:</para>

    <orderedlist>
      <listitem><para>Show general OS image information, including the image's
      <citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry> data,
      machine ID, partition information and more.</para></listitem>

      <listitem><para>Mount an OS image to a local directory. In this mode it will dissect the OS image and
      mount the included partitions according to their designation onto a directory and possibly
      sub-directories.</para></listitem>

      <listitem><para>Unmount an OS image from a local directory. In this mode it will recursively unmount
      the mounted partitions and remove the underlying loop device, including all the partition sub-devices.
      </para></listitem>

      <listitem><para>Copy files and directories in and out of an OS image.</para></listitem>
    </orderedlist>

    <para>The tool may operate on three types of OS images:</para>

    <orderedlist>
      <listitem><para>OS disk images containing a GPT partition table envelope, with partitions marked
      according to the <ulink url="https://uapi-group.org/specifications/specs/discoverable_partitions_specification">Discoverable Partitions
      Specification</ulink>.</para></listitem>

      <listitem><para>OS disk images containing just a plain file-system without an enveloping partition
      table. (This file system is assumed to be the root file system of the OS.)</para></listitem>

      <listitem><para>OS disk images containing a GPT or MBR partition table, with a single
      partition only. (This partition is assumed to contain the root file system of the OS.)</para></listitem>
    </orderedlist>

    <para>OS images may use any kind of Linux-supported file systems. In addition they may make use of LUKS
    disk encryption, and contain Verity integrity information. Note that qualifying OS images may be booted
    with <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
    <option>--image=</option> switch, and be used as root file system for system service using the
    <varname>RootImage=</varname> unit file setting, see
    <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>

    <para>Note that the partition table shown when invoked without command switch (as listed below) does not
    necessarily show all partitions included in the image, but just the partitions that are understood and
    considered part of an OS disk image. Specifically, partitions of unknown types are ignored, as well as
    duplicate partitions (i.e. more than one per partition type), as are root and <filename>/usr/</filename>
    partitions of architectures not compatible with the local system. In other words: this tool will display
    what it operates with when mounting the image. To display the complete list of partitions use a tool such
    as <citerefentry
    project='man-pages'><refentrytitle>fdisk</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>

    <para>The <command>systemd-dissect</command> command may be invoked as <command>mount.ddi</command> in
    which case it implements the <citerefentry
    project='man-pages'><refentrytitle>mount</refentrytitle><manvolnum>8</manvolnum></citerefentry> "external
    helper" interface. This ensures disk images compatible with <command>systemd-dissect</command> can be
    mounted directly by <command>mount</command> and <citerefentry
    project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>. For
    details see below.</para>

    <xi:include href="vpick.xml" xpointer="image"/>
  </refsect1>

  <refsect1>
    <title>Commands</title>

    <para>If neither of the command switches listed below are passed the specified disk image is opened and
    general information about the image and the contained partitions and their use is shown.</para>

    <variablelist>
      <varlistentry>
        <term><option>--mount</option></term>
        <term><option>-m</option></term>

        <listitem><para>Mount the specified OS image to the specified directory. This will dissect the image,
        determine the OS root file system  as well as possibly other partitions  and mount them to the
        specified directory. If the OS image contains multiple partitions marked with the <ulink
        url="https://uapi-group.org/specifications/specs/discoverable_partitions_specification">Discoverable Partitions Specification</ulink>
        multiple nested mounts are established. This command expects two arguments: a path to an image file
        and a path to a directory where to mount the image.</para>

        <para>To unmount an OS image mounted like this use the <option>--umount</option> operation.</para>

        <para>When the OS image contains LUKS encrypted or Verity integrity protected file systems
        appropriate volumes are automatically set up and marked for automatic disassembly when the image is
        unmounted.</para>

        <para>The OS image may either be specified as path to an OS image stored in a regular file or may
        refer to block device node (in the latter case the block device must be the "whole" device, i.e. not
        a partition device). (The other supported commands described here support this, too.)</para>

        <para>All mounted file systems are checked with the appropriate <citerefentry
        project='man-pages'><refentrytitle>fsck</refentrytitle><manvolnum>8</manvolnum></citerefentry>
        implementation in automatic fixing mode, unless explicitly turned off (<option>--fsck=no</option>) or
        read-only operation is requested (<option>--read-only</option>).</para>

        <para>Note that this functionality is also available in <citerefentry
        project='man-pages'><refentrytitle>mount</refentrytitle><manvolnum>8</manvolnum></citerefentry> via a
        command such as <command>mount -t ddi myimage.raw targetdir/</command>, as well as in <citerefentry
        project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>. For
        details, see below.</para>

        <xi:include href="version-info.xml" xpointer="v247"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-M</option></term>

        <listitem><para>This is a shortcut for <option>--mount --mkdir</option>.</para>

        <xi:include href="version-info.xml" xpointer="v247"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--umount</option></term>
        <term><option>-u</option></term>

        <listitem><para>Unmount an OS image from the specified directory. This command expects one argument:
        a directory where an OS image was mounted.</para>

        <para>All mounted partitions will be recursively unmounted, and the underlying loop device will be
        removed, along with all its partition sub-devices.</para>

        <xi:include href="version-info.xml" xpointer="v252"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-U</option></term>

        <listitem><para>This is a shortcut for <option>--umount --rmdir</option>.</para>

        <xi:include href="version-info.xml" xpointer="v252"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--attach</option></term>

        <listitem><para>Attach the specified disk image to an automatically allocated loopback block device,
        and print the path to the loopback block device to standard output. This is similar to an invocation
        of <command>losetup --find --show</command>, but will validate the image as DDI before attaching, and
        derive the correct sector size to use automatically. Moreover, it ensures the per-partition block
        devices are created before returning. Takes a path to a disk image file.</para>

        <xi:include href="version-info.xml" xpointer="v254"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--detach</option></term>

        <listitem><para>Detach the specified disk image from a loopback block device. This undoes the effect
        of <option>--attach</option> above. This expects either a path to a loopback block device as an
        argument, or the path to the backing image file. In the latter case it will automatically determine
        the right device to detach.</para>

        <xi:include href="version-info.xml" xpointer="v254"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--list</option></term>
        <term><option>-l</option></term>

        <listitem><para>Prints the paths of all the files and directories in the specified OS image or
        directory to standard output.</para>

        <xi:include href="version-info.xml" xpointer="v253"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--mtree</option></term>

        <listitem><para>Generates a BSD
        <citerefentry project='die-net'><refentrytitle>mtree</refentrytitle><manvolnum>8</manvolnum></citerefentry>
        compatible file manifest of the specified disk image or directory. This is useful for comparing image
        contents in detail, including inode information and other metadata. While the generated manifest will
        contain detailed inode information, it currently excludes extended attributes, file system
        capabilities, MAC labels,
        <citerefentry project='man-pages'><refentrytitle>chattr</refentrytitle><manvolnum>1</manvolnum></citerefentry>
        file flags,
        <citerefentry project='url'><refentrytitle url='https://btrfs.readthedocs.io/en/latest/btrfs-man5.html'>btrfs</refentrytitle><manvolnum>5</manvolnum></citerefentry>
        subvolume information, and various other file metadata. File content information is shown via a
        SHA256 digest. Additional fields might be added in future. Note that inode information such as link
        counts, inode numbers and timestamps is excluded from the output on purpose, as it typically
        complicates reproducibility.</para>

        <xi:include href="version-info.xml" xpointer="v253"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--with</option></term>

        <listitem><para>Runs the specified command with the specified OS image mounted. This will mount the
        image to a temporary directory, switch the current working directory to it, and invoke the specified
        command line as child process. Once the process ends it will unmount the image again, and remove the
        temporary directory. If no command is specified a shell is invoked. The image is mounted writable,
        use <option>--read-only</option> to switch to read-only operation. The invoked process will have the
        <varname>$SYSTEMD_DISSECT_ROOT</varname> environment variable set, containing the absolute path name
        of the temporary mount point, i.e. the same directory that is set as the current working
        directory. It will also have the <varname>$SYSTEMD_DISSECT_DEVICE</varname> environment variable set,
        containing the absolute path name of the loop device the image was attached to.</para>

        <xi:include href="version-info.xml" xpointer="v253"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--copy-from</option></term>
        <term><option>-x</option></term>

        <listitem><para>Copies a file or directory from the specified OS image or directory into the
        specified location on the host file system. Expects three arguments: a path to an image file or
        directory, a source path (relative to the image's root directory) and a destination path (relative to
        the current working directory, or an absolute path, both outside of the image). If the destination
        path is omitted or specified as dash (<literal>-</literal>), the specified file is written to
        standard output. If the source path in the image file system refers to a regular file it is copied to
        the destination path. In this case access mode, extended attributes and timestamps are copied as
        well, but file ownership is not. If the source path in the image refers to a directory, it is copied
        to the destination path, recursively with all containing files and directories. In this case the file
        ownership is copied too.</para>

        <xi:include href="version-info.xml" xpointer="v247"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--copy-to</option></term>
        <term><option>-a</option></term>

        <listitem><para>Copies a file or directory from the specified location in the host file system into
        the specified OS image or directory. Expects three arguments: a path to an image file or directory, a
        source path (relative to the current working directory, or an absolute path, both outside of the
        image) and a destination path (relative to the image's root directory). If the source path is omitted
        or specified as dash (<literal>-</literal>), the data to write is read from standard input. If the
        source path in the host file system refers to a regular file, it is copied to the destination path.
        In this case access mode, extended attributes and timestamps are copied as well, but file ownership
        is not. If the source path in the host file system refers to a directory it is copied to the
        destination path, recursively with all containing files and directories. In this case the file
        ownership is copied too.</para>

        <para>As with <option>--mount</option> file system checks are implicitly run before the copy
        operation begins.</para>

        <xi:include href="version-info.xml" xpointer="v247"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--make-archive</option></term>

        <listitem><para>Generates an archive file from the specified disk image. Expects two arguments: the
        path to the disk image and optionally the output archive file path. If the latter is omitted the
        archive is written to standard output. The archive file format is determined automatically from the
        specified output archive file name, e.g. any path suffixed with <literal>.tar.xz</literal> will
        result in an xz compressed UNIX tarball (if the path is omitted an uncompressed UNIX tarball is
        created). See
        <citerefentry><refentrytitle>libarchive</refentrytitle><manvolnum>3</manvolnum></citerefentry> for a
        list of supported archive formats and compression schemes.</para>

        <xi:include href="version-info.xml" xpointer="v256"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--discover</option></term>

        <listitem><para>Show a list of DDIs in well-known directories. This will show machine, portable
        service and system/configuration extension disk images in the usual directories
        <filename>/usr/lib/machines/</filename>, <filename>/usr/lib/portables/</filename>,
        <filename>/usr/lib/confexts/</filename>, <filename>/var/lib/machines/</filename>,
        <filename>/var/lib/portables/</filename>, <filename>/var/lib/extensions/</filename> and so
        on.</para>

        <xi:include href="version-info.xml" xpointer="v253"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--validate</option></term>

        <listitem><para>Validates the partition arrangement of a disk image (DDI), and ensures it matches the
        image policy specified via <option>--image-policy=</option>, if one is specified. This parses the
        partition table and probes the file systems in the image, but does not attempt to mount them (nor to
        set up disk encryption/authentication via LUKS/Verity). It does this taking the configured image
        dissection policy into account. Since this operation does not mount file systems, this command         unlike all other commands implemented by this tool  requires no privileges other than the ability to
        access the specified file. Prints "OK" and returns zero if the image appears to be in order and
        matches the specified image dissection policy. Otherwise prints an error message and returns
        non-zero.</para>

        <xi:include href="version-info.xml" xpointer="v254"/></listitem>
      </varlistentry>

      <xi:include href="standard-options.xml" xpointer="help" />
      <xi:include href="standard-options.xml" xpointer="version" />
    </variablelist>

  </refsect1>

  <refsect1>
    <title>Options</title>

    <para>The following options are understood:</para>

    <variablelist>
      <varlistentry>
        <term><option>--read-only</option></term>
        <term><option>-r</option></term>

        <listitem><para>Operate in read-only mode. By default <option>--mount</option> will establish
        writable mount points. If this option is specified they are established in read-only mode
        instead.</para>

        <xi:include href="version-info.xml" xpointer="v247"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--fsck=no</option></term>

        <listitem><para>Turn off automatic file system checking. By default when an image is accessed for
        writing (by <option>--mount</option> or <option>--copy-to</option>) the file systems contained in the
        OS image are automatically checked using the appropriate <citerefentry
        project='man-pages'><refentrytitle>fsck</refentrytitle><manvolnum>8</manvolnum></citerefentry>
        command, in automatic fixing mode. This behavior may be switched off using
        <option>--fsck=no</option>.</para>

        <xi:include href="version-info.xml" xpointer="v247"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--growfs=no</option></term>

        <listitem><para>Turn off automatic growing of accessed file systems to their partition size, if
        marked for that in the GPT partition table. By default when an image is accessed for writing (by
        <option>--mount</option> or <option>--copy-to</option>) the file systems contained in the OS image
        are automatically grown to their partition sizes, if bit 59 in the GPT partition flags is set for
        partition types that are defined by the <ulink
        url="https://uapi-group.org/specifications/specs/discoverable_partitions_specification">Discoverable Partitions Specification</ulink>. This
        behavior may be switched off using <option>--growfs=no</option>. File systems are grown automatically
        on access if all of the following conditions are met:</para>
        <orderedlist>
          <listitem><para>The file system is mounted writable</para></listitem>
          <listitem><para>The file system currently is smaller than the partition it is contained in (and thus can be grown)</para></listitem>
          <listitem><para>The image contains a GPT partition table</para></listitem>
          <listitem><para>The file system is stored on a partition defined by the Discoverable Partitions Specification</para></listitem>
          <listitem><para>Bit 59 of the GPT partition flags for this partition is set, as per specification</para></listitem>
          <listitem><para>The <option>--growfs=no</option> option is not passed.</para></listitem>
        </orderedlist>

          <xi:include href="version-info.xml" xpointer="v249"/>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--mkdir</option></term>

        <listitem><para>If combined with <option>--mount</option> the directory to mount the OS image to is
        created if it is missing. Note that the directory is not automatically removed when the disk image is
        unmounted again.</para>

        <xi:include href="version-info.xml" xpointer="v247"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--rmdir</option></term>

        <listitem><para>If combined with <option>--umount</option> the specified directory where the OS image
        is mounted is removed after unmounting the OS image.</para>

        <xi:include href="version-info.xml" xpointer="v252"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--discard=</option></term>

        <listitem><para>Takes one of <literal>disabled</literal>, <literal>loop</literal>,
        <literal>all</literal>, <literal>crypto</literal>. If <literal>disabled</literal> the image is
        accessed with empty block discarding turned off. If <literal>loop</literal> discarding is enabled if
        operating on a regular file. If <literal>crypt</literal> discarding is enabled even on encrypted file
        systems. If <literal>all</literal> discarding is unconditionally enabled.</para>

        <xi:include href="version-info.xml" xpointer="v247"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--in-memory</option></term>

        <listitem><para>If specified an in-memory copy of the specified disk image is used. This may be used
        to operate with write-access on a (possibly read-only) image, without actually modifying the original
        file. This may also be used in order to operate on a disk image without keeping the originating file
        system busy, in order to allow it to be unmounted.</para>

        <xi:include href="version-info.xml" xpointer="v253"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--root-hash=</option></term>
        <term><option>--root-hash-sig=</option></term>
        <term><option>--verity-data=</option></term>

        <listitem><para>Configure various aspects of Verity data integrity for the OS image. Option
        <option>--root-hash=</option> specifies a hex-encoded top-level Verity hash to use for setting up the
        Verity integrity protection. Option <option>--root-hash-sig=</option> specifies the path to a file
        containing a PKCS#7 signature for the hash. This signature is passed to the kernel during activation,
        which will match it against signature keys available in the kernel keyring.  Option
        <option>--verity-data=</option> specifies a path to a file with the Verity data to use for the OS
        image, in case it is stored in a detached file. It is recommended to embed the Verity data directly
        in the image, using the Verity mechanisms in the <ulink
        url="https://uapi-group.org/specifications/specs/discoverable_partitions_specification">Discoverable Partitions Specification</ulink>.
        </para>

        <xi:include href="version-info.xml" xpointer="v247"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--loop-ref=</option></term>

        <listitem><para>Configures the "reference" string the kernel shall report as backing file for the
        loopback block device. While this is supposed to be a path or filename referencing the backing file,
        this is not enforced and the kernel accepts arbitrary free-form strings, chosen by the user. Accepts
        arbitrary strings up to a length of 63 characters. This sets the kernel's
        <literal>.lo_file_name</literal> field for the block device. Note this is distinct from the
        <filename>/sys/class/block/loopX/loop/backing_file</filename> attribute file that always reports a
        path referring to the actual backing file. The latter is subject to mount namespace translation, the
        former is not.</para>

        <para>This setting is particularly useful in combination with the <option>--attach</option> command,
        as it allows later referencing the allocated loop device via
        <filename>/dev/disk/by-loop-ref/…</filename> symlinks. Example: first, set up the loopback device
        via <command>systemd-dissect attach --loop-ref=quux foo.raw</command>, and then reference it in a
        command via the specified filename: <command>cfdisk /dev/disk/by-loop-ref/quux</command>.
        </para>

        <xi:include href="version-info.xml" xpointer="v254"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--mtree-hash=no</option></term>

        <listitem><para>If combined with <option>--mtree</option>, turns off inclusion of file hashes in the
        mtree output. This makes the <option>--mtree</option> faster when operating on large images.
        </para>

        <xi:include href="version-info.xml" xpointer="v254"/></listitem>
      </varlistentry>

      <xi:include href="standard-options.xml" xpointer="image-policy-open" />
      <xi:include href="standard-options.xml" xpointer="no-pager" />
      <xi:include href="standard-options.xml" xpointer="no-legend" />
      <xi:include href="standard-options.xml" xpointer="json" />
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Exit status</title>

    <para>On success, 0 is returned, a non-zero failure code otherwise. If the <option>--with</option>
    command is used the exit status of the invoked command is propagated.</para>
  </refsect1>

  <refsect1>
    <title>Invocation as <command>/sbin/mount.ddi</command></title>

    <para>The <command>systemd-dissect</command> executable may be symlinked to
    <filename>/sbin/mount.ddi</filename>. If invoked through that it implements <citerefentry
    project='man-pages'><refentrytitle>mount</refentrytitle><manvolnum>8</manvolnum></citerefentry>'s
    "external helper" interface for the (pseudo) file system type <literal>ddi</literal>. This means
    conformant disk images may be mounted directly via</para>

    <programlisting># mount -t ddi myimage.raw targetdir/</programlisting>

    <para>in a fashion mostly equivalent to:</para>

    <programlisting># systemd-dissect --mount myimage.raw targetdir/</programlisting>

    <para>Note that since a single DDI may contain multiple file systems it should later be unmounted with
    <command>umount -R targetdir/</command>, for recursive operation.</para>

    <para>This functionality is particularly useful to mount DDIs automatically at boot via simple
    <filename>/etc/fstab</filename> entries. For example:</para>

    <programlisting>/path/to/myimage.raw /images/myimage/ ddi defaults 0 0</programlisting>

    <para>When invoked this way the mount options <literal>ro</literal>, <literal>rw</literal>,
    <literal>discard</literal>, <literal>nodiscard</literal> map to the corresponding options listed above
    (i.e. <option>--read-only</option>, <option>--discard=all</option>,
    <option>--discard=disabled</option>). Mount options are <emphasis>not</emphasis> generically passed on to
    the file systems inside the images.</para>
  </refsect1>

  <refsect1>
    <title>Examples</title>

    <example>
      <title>Generate a tarball from an OS disk image (<option>--with</option>)</title>

      <programlisting># systemd-dissect --with foo.raw tar cz . >foo.tar.gz</programlisting>
    </example>

    <para>or alternatively just:</para>

    <example>
      <title>Generate a tarball from an OS disk image (<option>--make-archive</option>)</title>

      <programlisting># systemd-dissect --make-archive foo.raw foo.tar.gz</programlisting>
    </example>
  </refsect1>

  <refsect1>
    <title>See Also</title>
    <para><simplelist type="inline">
      <member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
      <member><citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
      <member><citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
      <member><citerefentry><refentrytitle>systemd.v</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
      <member><ulink url="https://uapi-group.org/specifications/specs/discoverable_partitions_specification">Discoverable Partitions Specification</ulink></member>
      <member><citerefentry project='man-pages'><refentrytitle>mount</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
      <member><citerefentry project='man-pages'><refentrytitle>umount</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
      <member><citerefentry project='man-pages'><refentrytitle>fdisk</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
    </simplelist></para>
  </refsect1>

</refentry>