man/systemd-dissect.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
   5
   6 <refentry id="systemd-dissect" conditional='HAVE_BLKID'
   7     xmlns:xi="http://www.w3.org/2001/XInclude">
   8
   9   <refentryinfo>
  10     <title>systemd-dissect</title>
  11     <productname>systemd</productname>
  12   </refentryinfo>
  13
  14   <refmeta>
  15     <refentrytitle>systemd-dissect</refentrytitle>
  16     <manvolnum>1</manvolnum>
  17   </refmeta>
  18
  19   <refnamediv>
  20     <refname>systemd-dissect</refname>
  21     <refname>mount.ddi</refname>
  22     <refpurpose>Dissect Discoverable Disk Images (DDIs)</refpurpose>
  23   </refnamediv>
  24
  25   <refsynopsisdiv>
  26     <cmdsynopsis>
  27       <command>systemd-dissect <arg choice="opt" rep="repeat">OPTIONS</arg> <arg choice="plain"><replaceable>IMAGE</replaceable></arg></command>
  28     </cmdsynopsis>
  29     <cmdsynopsis>
  30       <command>systemd-dissect <arg choice="opt" rep="repeat">OPTIONS</arg> <option>--mount</option> <arg choice="plain"><replaceable>IMAGE</replaceable></arg> <arg choice="plain"><replaceable>PATH</replaceable></arg></command>
  31     </cmdsynopsis>
  32     <cmdsynopsis>
  33       <command>systemd-dissect <arg choice="opt" rep="repeat">OPTIONS</arg> <option>--umount</option> <arg choice="plain"><replaceable>PATH</replaceable></arg></command>
  34     </cmdsynopsis>
  35     <cmdsynopsis>
  36       <command>systemd-dissect <arg choice="opt" rep="repeat">OPTIONS</arg> <option>--attach</option> <arg choice="plain"><replaceable>IMAGE</replaceable></arg></command>
  37     </cmdsynopsis>
  38     <cmdsynopsis>
  39       <command>systemd-dissect <arg choice="opt" rep="repeat">OPTIONS</arg> <option>--detach</option> <arg choice="plain"><replaceable>PATH</replaceable></arg></command>
  40     </cmdsynopsis>
  41     <cmdsynopsis>
  42       <command>systemd-dissect <arg choice="opt" rep="repeat">OPTIONS</arg> <option>--list</option> <arg choice="plain"><replaceable>IMAGE</replaceable></arg></command>
  43     </cmdsynopsis>
  44     <cmdsynopsis>
  45       <command>systemd-dissect <arg choice="opt" rep="repeat">OPTIONS</arg> <option>--mtree</option> <arg choice="plain"><replaceable>IMAGE</replaceable></arg></command>
  46     </cmdsynopsis>
  47     <cmdsynopsis>
  48       <command>systemd-dissect <arg choice="opt" rep="repeat">OPTIONS</arg> <option>--with</option> <arg choice="plain"><replaceable>IMAGE</replaceable></arg> <arg choice="opt" rep="repeat"><replaceable>COMMAND</replaceable></arg></command>
  49     </cmdsynopsis>
  50     <cmdsynopsis>
  51       <command>systemd-dissect <arg choice="opt" rep="repeat">OPTIONS</arg> <option>--copy-from</option> <arg choice="plain"><replaceable>IMAGE</replaceable></arg> <arg choice="plain"><replaceable>PATH</replaceable></arg> <arg choice="opt"><replaceable>TARGET</replaceable></arg></command>
  52     </cmdsynopsis>
  53     <cmdsynopsis>
  54       <command>systemd-dissect <arg choice="opt" rep="repeat">OPTIONS</arg> <option>--copy-to</option> <arg choice="plain"><replaceable>IMAGE</replaceable></arg> <arg choice="opt"><replaceable>SOURCE</replaceable></arg> <arg choice="plain"><replaceable>PATH</replaceable></arg></command>
  55     </cmdsynopsis>
  56   </refsynopsisdiv>
  57
  58   <refsect1>
  59     <title>Description</title>
  60
  61     <para><command>systemd-dissect</command> is a tool for introspecting and interacting with file system OS
  62     disk images, specifically Discoverable Disk Images (DDIs). It supports four different operations:</para>
  63
  64     <orderedlist>
  65       <listitem><para>Show general OS image information, including the image's
  66       <citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry> data,
  67       machine ID, partition information and more.</para></listitem>
  68
  69       <listitem><para>Mount an OS image to a local directory. In this mode it will dissect the OS image and
  70       mount the included partitions according to their designation onto a directory and possibly
  71       sub-directories.</para></listitem>
  72
  73       <listitem><para>Unmount an OS image from a local directory. In this mode it will recursively unmount
  74       the mounted partitions and remove the underlying loop device, including all the partition sub-devices.
  75       </para></listitem>
  76
  77       <listitem><para>Copy files and directories in and out of an OS image.</para></listitem>
  78     </orderedlist>
  79
  80     <para>The tool may operate on three types of OS images:</para>
  81
  82     <orderedlist>
  83       <listitem><para>OS disk images containing a GPT partition table envelope, with partitions marked
  84       according to the <ulink url="https://uapi-group.org/specifications/specs/discoverable_partitions_specification">Discoverable Partitions
  85       Specification</ulink>.</para></listitem>
  86
  87       <listitem><para>OS disk images containing just a plain file-system without an enveloping partition
  88       table. (This file system is assumed to be the root file system of the OS.)</para></listitem>
  89
  90       <listitem><para>OS disk images containing a GPT or MBR partition table, with a single
  91       partition only. (This partition is assumed to contain the root file system of the OS.)</para></listitem>
  92     </orderedlist>
  93
  94     <para>OS images may use any kind of Linux-supported file systems. In addition they may make use of LUKS
  95     disk encryption, and contain Verity integrity information. Note that qualifying OS images may be booted
  96     with <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
  97     <option>--image=</option> switch, and be used as root file system for system service using the
  98     <varname>RootImage=</varname> unit file setting, see
  99     <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 100
 101     <para>Note that the partition table shown when invoked without command switch (as listed below) does not
 102     necessarily show all partitions included in the image, but just the partitions that are understood and
 103     considered part of an OS disk image. Specifically, partitions of unknown types are ignored, as well as
 104     duplicate partitions (i.e. more than one per partition type), as are root and <filename>/usr/</filename>
 105     partitions of architectures not compatible with the local system. In other words: this tool will display
 106     what it operates with when mounting the image. To display the complete list of partitions use a tool such
 107     as <citerefentry
 108     project='man-pages'><refentrytitle>fdisk</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 109
 110     <para>The <command>systemd-dissect</command> command may be invoked as <command>mount.ddi</command> in
 111     which case it implements the <citerefentry
 112     project='man-pages'><refentrytitle>mount</refentrytitle><manvolnum>8</manvolnum></citerefentry> "external
 113     helper" interface. This ensures disk images compatible with <command>systemd-dissect</command> can be
 114     mounted directly by <command>mount</command> and <citerefentry
 115     project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>. For
 116     details see below.</para>
 117   </refsect1>
 118
 119   <refsect1>
 120     <title>Commands</title>
 121
 122     <para>If neither of the command switches listed below are passed the specified disk image is opened and
 123     general information about the image and the contained partitions and their use is shown.</para>
 124
 125     <variablelist>
 126       <varlistentry>
 127         <term><option>--mount</option></term>
 128         <term><option>-m</option></term>
 129
 130         <listitem><para>Mount the specified OS image to the specified directory. This will dissect the image,
 131         determine the OS root file system — as well as possibly other partitions — and mount them to the
 132         specified directory. If the OS image contains multiple partitions marked with the <ulink
 133         url="https://uapi-group.org/specifications/specs/discoverable_partitions_specification">Discoverable Partitions Specification</ulink>
 134         multiple nested mounts are established. This command expects two arguments: a path to an image file
 135         and a path to a directory where to mount the image.</para>
 136
 137         <para>To unmount an OS image mounted like this use the <option>--umount</option> operation.</para>
 138
 139         <para>When the OS image contains LUKS encrypted or Verity integrity protected file systems
 140         appropriate volumes are automatically set up and marked for automatic disassembly when the image is
 141         unmounted.</para>
 142
 143         <para>The OS image may either be specified as path to an OS image stored in a regular file or may
 144         refer to block device node (in the latter case the block device must be the "whole" device, i.e. not
 145         a partition device). (The other supported commands described here support this, too.)</para>
 146
 147         <para>All mounted file systems are checked with the appropriate <citerefentry
 148         project='man-pages'><refentrytitle>fsck</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 149         implementation in automatic fixing mode, unless explicitly turned off (<option>--fsck=no</option>) or
 150         read-only operation is requested (<option>--read-only</option>).</para>
 151
 152         <para>Note that this functionality is also available in <citerefentry
 153         project='man-pages'><refentrytitle>mount</refentrytitle><manvolnum>8</manvolnum></citerefentry> via a
 154         command such as <command>mount -t ddi myimage.raw targetdir/</command>, as well as in <citerefentry
 155         project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>. For
 156         details, see below.</para></listitem>
 157       </varlistentry>
 158
 159       <varlistentry>
 160         <term><option>-M</option></term>
 161
 162         <listitem><para>This is a shortcut for <option>--mount --mkdir</option>.</para></listitem>
 163       </varlistentry>
 164
 165       <varlistentry>
 166         <term><option>--umount</option></term>
 167         <term><option>-u</option></term>
 168
 169         <listitem><para>Unmount an OS image from the specified directory. This command expects one argument:
 170         a directory where an OS image was mounted.</para>
 171
 172         <para>All mounted partitions will be recursively unmounted, and the underlying loop device will be
 173         removed, along with all its partition sub-devices.</para></listitem>
 174       </varlistentry>
 175
 176       <varlistentry>
 177         <term><option>-U</option></term>
 178
 179         <listitem><para>This is a shortcut for <option>--umount --rmdir</option>.</para></listitem>
 180       </varlistentry>
 181
 182       <varlistentry>
 183         <term><option>--attach</option></term>
 184
 185         <listitem><para>Attach the specified disk image to an automatically allocated loopback block device,
 186         and print the path to the loopback block device to standard output. This is similar to an invocation
 187         of <command>losetup --find --show</command>, but will validate the image as DDI before attaching, and
 188         derive the correct sector size to use automatically. Moreover, it ensures the per-partition block
 189         devices are created before returning. Takes a path to a disk image file.</para></listitem>
 190       </varlistentry>
 191
 192       <varlistentry>
 193         <term><option>--detach</option></term>
 194
 195         <listitem><para>Detach the specified disk image from a loopback block device. This undoes the effect
 196         of <option>--attach</option> above. This expects either a path to a loopback block device as an
 197         argument, or the path to the backing image file. In the latter case it will automatically determine
 198         the right device to detach.</para></listitem>
 199       </varlistentry>
 200
 201       <varlistentry>
 202         <term><option>--list</option></term>
 203         <term><option>-l</option></term>
 204
 205         <listitem><para>Prints the paths of all the files and directories in the specified OS image or
 206         directory to standard output.</para></listitem>
 207       </varlistentry>
 208
 209       <varlistentry>
 210         <term><option>--mtree</option></term>
 211         <term><option>-l</option></term>
 212
 213         <listitem><para>Generates a BSD
 214         <citerefentry project='die-net'><refentrytitle>mtree</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 215         compatible file manifest of the specified disk image or directory. This is useful for comparing image
 216         contents in detail, including inode information and other metadata. While the generated manifest will
 217         contain detailed inode information, it currently excludes extended attributes, file system
 218         capabilities, MAC labels,
 219         <citerefentry project='man-pages'><refentrytitle>chattr</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 220         file flags,
 221         <citerefentry project='url'><refentrytitle url='https://btrfs.wiki.kernel.org/index.php/Manpage/btrfs(5)'>btrfs</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 222         subvolume information, and various other file metadata. File content information is shown via a
 223         SHA256 digest. Additional fields might be added in future. Note that inode information such as link
 224         counts, inode numbers and timestamps is excluded from the output on purpose, as it typically
 225         complicates reproducibility.</para></listitem>
 226       </varlistentry>
 227
 228       <varlistentry>
 229         <term><option>--with</option></term>
 230
 231         <listitem><para>Runs the specified command with the specified OS image mounted. This will mount the
 232         image to a temporary directory, switch the current working directory to it, and invoke the specified
 233         command line as child process. Once the process ends it will unmount the image again, and remove the
 234         temporary directory. If no command is specified a shell is invoked. The image is mounted writable,
 235         use <option>--read-only</option> to switch to read-only operation. The invoked process will have the
 236         <varname>$SYSTEMD_DISSECT_ROOT</varname> environment variable set, containing the absolute path name
 237         of the temporary mount point, i.e. the same directory that is set as the current working
 238         directory. It will also have the <varname>$SYSTEMD_DISSECT_DEVICE</varname> environment variable set,
 239         containing the absolute path name of the loop device the image was attached to.</para></listitem>
 240       </varlistentry>
 241
 242       <varlistentry>
 243         <term><option>--copy-from</option></term>
 244         <term><option>-x</option></term>
 245
 246         <listitem><para>Copies a file or directory from the specified OS image or directory into the
 247         specified location on the host file system. Expects three arguments: a path to an image file or
 248         directory, a source path (relative to the image's root directory) and a destination path (relative to
 249         the current working directory, or an absolute path, both outside of the image). If the destination
 250         path is omitted or specified as dash (<literal>-</literal>), the specified file is written to
 251         standard output. If the source path in the image file system refers to a regular file it is copied to
 252         the destination path. In this case access mode, extended attributes and timestamps are copied as
 253         well, but file ownership is not. If the source path in the image refers to a directory, it is copied
 254         to the destination path, recursively with all containing files and directories. In this case the file
 255         ownership is copied too.</para></listitem>
 256       </varlistentry>
 257
 258       <varlistentry>
 259         <term><option>--copy-to</option></term>
 260         <term><option>-a</option></term>
 261
 262         <listitem><para>Copies a file or directory from the specified location in the host file system into
 263         the specified OS image or directory. Expects three arguments: a path to an image file or directory, a
 264         source path (relative to the current working directory, or an absolute path, both outside of the
 265         image) and a destination path (relative to the image's root directory). If the source path is omitted
 266         or specified as dash (<literal>-</literal>), the data to write is read from standard input. If the
 267         source path in the host file system refers to a regular file, it is copied to the destination path.
 268         In this case access mode, extended attributes and timestamps are copied as well, but file ownership
 269         is not. If the source path in the host file system refers to a directory it is copied to the
 270         destination path, recursively with all containing files and directories. In this case the file
 271         ownership is copied too.</para>
 272
 273         <para>As with <option>--mount</option> file system checks are implicitly run before the copy
 274         operation begins.</para></listitem>
 275       </varlistentry>
 276
 277       <varlistentry>
 278         <term><option>--discover</option></term>
 279
 280         <listitem><para>Show a list of DDIs in well-known directories. This will show machine, portable
 281         service and system/configuration extension disk images in the usual directories
 282         <filename>/usr/lib/machines/</filename>, <filename>/usr/lib/portables/</filename>,
 283         <filename>/usr/lib/confexts/</filename>, <filename>/var/lib/machines/</filename>,
 284         <filename>/var/lib/portables/</filename>, <filename>/var/lib/extensions/</filename> and so
 285         on.</para></listitem>
 286       </varlistentry>
 287
 288       <varlistentry>
 289         <term><option>--validate</option></term>
 290
 291         <listitem><para>Validates the partition arrangement of a disk image (DDI), and ensures it matches the
 292         image policy specified via <option>--image-policy=</option>, if one is specified. This parses the
 293         partition table and probes the file systems in the image, but does not attempt to mount them (nor to
 294         set up disk encryption/authentication via LUKS/Verity). It does this taking the configured image
 295         dissection policy into account. Since this operation does not mount file systems, this command –
 296         unlike all other commands implemented by this tool – requires no privileges other than the ability to
 297         access the specified file. Prints "OK" and returns zero if the image appears to be in order and
 298         matches the specified image dissection policy. Otherwise prints an error message and returns
 299         non-zero.</para></listitem>
 300       </varlistentry>
 301
 302       <xi:include href="standard-options.xml" xpointer="help" />
 303       <xi:include href="standard-options.xml" xpointer="version" />
 304     </variablelist>
 305
 306   </refsect1>
 307
 308   <refsect1>
 309     <title>Options</title>
 310
 311     <para>The following options are understood:</para>
 312
 313     <variablelist>
 314       <varlistentry>
 315         <term><option>--read-only</option></term>
 316         <term><option>-r</option></term>
 317
 318         <listitem><para>Operate in read-only mode. By default <option>--mount</option> will establish
 319         writable mount points. If this option is specified they are established in read-only mode
 320         instead.</para></listitem>
 321       </varlistentry>
 322
 323       <varlistentry>
 324         <term><option>--fsck=no</option></term>
 325
 326         <listitem><para>Turn off automatic file system checking. By default when an image is accessed for
 327         writing (by <option>--mount</option> or <option>--copy-to</option>) the file systems contained in the
 328         OS image are automatically checked using the appropriate <citerefentry
 329         project='man-pages'><refentrytitle>fsck</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 330         command, in automatic fixing mode. This behavior may be switched off using
 331         <option>--fsck=no</option>.</para></listitem>
 332       </varlistentry>
 333
 334       <varlistentry>
 335         <term><option>--growfs=no</option></term>
 336
 337         <listitem><para>Turn off automatic growing of accessed file systems to their partition size, if
 338         marked for that in the GPT partition table. By default when an image is accessed for writing (by
 339         <option>--mount</option> or <option>--copy-to</option>) the file systems contained in the OS image
 340         are automatically grown to their partition sizes, if bit 59 in the GPT partition flags is set for
 341         partition types that are defined by the <ulink
 342         url="https://uapi-group.org/specifications/specs/discoverable_partitions_specification">Discoverable Partitions Specification</ulink>. This
 343         behavior may be switched off using <option>--growfs=no</option>. File systems are grown automatically
 344         on access if all of the following conditions are met:</para>
 345         <orderedlist>
 346           <listitem><para>The file system is mounted writable</para></listitem>
 347           <listitem><para>The file system currently is smaller than the partition it is contained in (and thus can be grown)</para></listitem>
 348           <listitem><para>The image contains a GPT partition table</para></listitem>
 349           <listitem><para>The file system is stored on a partition defined by the Discoverable Partitions Specification</para></listitem>
 350           <listitem><para>Bit 59 of the GPT partition flags for this partition is set, as per specification</para></listitem>
 351           <listitem><para>The <option>--growfs=no</option> option is not passed.</para></listitem>
 352         </orderedlist>
 353         </listitem>
 354       </varlistentry>
 355
 356       <varlistentry>
 357         <term><option>--mkdir</option></term>
 358
 359         <listitem><para>If combined with <option>--mount</option> the directory to mount the OS image to is
 360         created if it is missing. Note that the directory is not automatically removed when the disk image is
 361         unmounted again.</para></listitem>
 362       </varlistentry>
 363
 364       <varlistentry>
 365         <term><option>--rmdir</option></term>
 366
 367         <listitem><para>If combined with <option>--umount</option> the specified directory where the OS image
 368         is mounted is removed after unmounting the OS image.</para></listitem>
 369       </varlistentry>
 370
 371       <varlistentry>
 372         <term><option>--discard=</option></term>
 373
 374         <listitem><para>Takes one of <literal>disabled</literal>, <literal>loop</literal>,
 375         <literal>all</literal>, <literal>crypto</literal>. If <literal>disabled</literal> the image is
 376         accessed with empty block discarding turned off. If <literal>loop</literal> discarding is enabled if
 377         operating on a regular file. If <literal>crypt</literal> discarding is enabled even on encrypted file
 378         systems. If <literal>all</literal> discarding is unconditionally enabled.</para></listitem>
 379       </varlistentry>
 380
 381       <varlistentry>
 382         <term><option>--in-memory</option></term>
 383
 384         <listitem><para>If specified an in-memory copy of the specified disk image is used. This may be used
 385         to operate with write-access on a (possibly read-only) image, without actually modifying the original
 386         file. This may also be used in order to operate on a disk image without keeping the originating file
 387         system busy, in order to allow it to be unmounted.</para></listitem>
 388       </varlistentry>
 389
 390       <varlistentry>
 391         <term><option>--root-hash=</option></term>
 392         <term><option>--root-hash-sig=</option></term>
 393         <term><option>--verity-data=</option></term>
 394
 395         <listitem><para>Configure various aspects of Verity data integrity for the OS image. Option
 396         <option>--root-hash=</option> specifies a hex-encoded top-level Verity hash to use for setting up the
 397         Verity integrity protection. Option <option>--root-hash-sig=</option> specifies the path to a file
 398         containing a PKCS#7 signature for the hash. This signature is passed to the kernel during activation,
 399         which will match it against signature keys available in the kernel keyring.  Option
 400         <option>--verity-data=</option> specifies a path to a file with the Verity data to use for the OS
 401         image, in case it is stored in a detached file. It is recommended to embed the Verity data directly
 402         in the image, using the Verity mechanisms in the <ulink
 403         url="https://uapi-group.org/specifications/specs/discoverable_partitions_specification">Discoverable Partitions Specification</ulink>.
 404         </para></listitem>
 405       </varlistentry>
 406
 407       <varlistentry>
 408         <term><option>--loop-ref=</option></term>
 409
 410         <listitem><para>Configures the "reference" string the kernel shall report as backing file for the
 411         loopback block device. While this is supposed to be a path or filename referencing the backing file,
 412         this is not enforced and the kernel accepts arbitrary free-form strings, chosen by the user. Accepts
 413         arbitrary strings up to a length of 63 characters. This sets the kernel's
 414         <literal>.lo_file_name</literal> field for the block device. Note this is distinct from the
 415         <filename>/sys/class/block/loopX/loop/backing_file</filename> attribute file that always reports a
 416         path referring to the actual backing file. The latter is subject to mount namespace translation, the
 417         former is not.</para>
 418
 419         <para>This setting is particularly useful in combination with the <option>--attach</option> command,
 420         as it allows later referencing the allocated loop device via
 421         <filename>/dev/disk/by-loop-ref/…</filename> symlinks. Example: first, set up the loopback device
 422         via <command>systemd-dissect attach --loop-ref=quux foo.raw</command>, and then reference it in a
 423         command via the specified filename: <command>cfdisk /dev/disk/by-loop-ref/quux</command>.
 424         </para></listitem>
 425       </varlistentry>
 426
 427       <varlistentry>
 428         <term><option>--mtree-hash=no</option></term>
 429
 430         <listitem><para>If combined with <option>--mtree</option>, turns off inclusion of file hashes in the
 431         mtree output. This makes the <option>--mtree</option> faster when operating on large images.
 432         </para></listitem>
 433       </varlistentry>
 434
 435       <xi:include href="standard-options.xml" xpointer="image-policy-open" />
 436       <xi:include href="standard-options.xml" xpointer="no-pager" />
 437       <xi:include href="standard-options.xml" xpointer="no-legend" />
 438       <xi:include href="standard-options.xml" xpointer="json" />
 439     </variablelist>
 440   </refsect1>
 441
 442   <refsect1>
 443     <title>Exit status</title>
 444
 445     <para>On success, 0 is returned, a non-zero failure code otherwise. If the <option>--with</option>
 446     command is used the exit status of the invoked command is propagated.</para>
 447   </refsect1>
 448
 449   <refsect1>
 450     <title>Invocation as <command>/sbin/mount.ddi</command></title>
 451
 452     <para>The <command>systemd-dissect</command> executable may be symlinked to
 453     <filename>/sbin/mount.ddi</filename>. If invoked through that it implements <citerefentry
 454     project='man-pages'><refentrytitle>mount</refentrytitle><manvolnum>8</manvolnum></citerefentry>'s
 455     "external helper" interface for the (pseudo) file system type <literal>ddi</literal>. This means
 456     conformant disk images may be mounted directly via</para>
 457
 458     <programlisting># mount -t ddi myimage.raw targetdir/</programlisting>
 459
 460     <para>in a fashion mostly equivalent to:</para>
 461
 462     <programlisting># systemd-dissect --mount myimage.raw targetdir/</programlisting>
 463
 464     <para>Note that since a single DDI may contain multiple file systems it should later be unmounted with
 465     <command>umount -R targetdir/</command>, for recursive operation.</para>
 466
 467     <para>This functionality is particularly useful to mount DDIs automatically at boot via simple
 468     <filename>/etc/fstab</filename> entries. For example:</para>
 469
 470     <programlisting>/path/to/myimage.raw /images/myimage/ ddi defaults 0 0</programlisting>
 471
 472     <para>When invoked this way the mount options <literal>ro</literal>, <literal>rw</literal>,
 473     <literal>discard</literal>, <literal>nodiscard</literal> map to the corresponding options listed above
 474     (i.e. <option>--read-only</option>, <option>--discard=all</option>,
 475     <option>--discard=disabled</option>). Mount options are <emphasis>not</emphasis> generically passed on to
 476     the file systems inside the images.</para>
 477   </refsect1>
 478
 479   <refsect1>
 480     <title>Examples</title>
 481
 482     <example>
 483       <title>Generate a tarball from an OS disk image</title>
 484
 485       <programlisting># systemd-dissect --with foo.raw tar cz . >foo.tar.gz</programlisting>
 486     </example>
 487   </refsect1>
 488
 489   <refsect1>
 490     <title>See Also</title>
 491     <para>
 492       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 493       <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 494       <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 495       <ulink url="https://uapi-group.org/specifications/specs/discoverable_partitions_specification">Discoverable Partitions Specification</ulink>,
 496       <citerefentry project='man-pages'><refentrytitle>mount</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 497       <citerefentry project='man-pages'><refentrytitle>umount</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 498       <citerefentry project='man-pages'><refentrytitle>fdisk</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 499     </para>
 500   </refsect1>
 501
 502 </refentry>