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281 lines
15 KiB
XML
281 lines
15 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="systemd-dissect" conditional='HAVE_BLKID'
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xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>systemd-dissect</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>systemd-dissect</refentrytitle>
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<manvolnum>1</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd-dissect</refname>
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<refpurpose>Dissect file system OS images</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<cmdsynopsis>
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<command>systemd-dissect <arg choice="opt" rep="repeat">OPTIONS</arg> <arg choice="plain"><replaceable>IMAGE</replaceable></arg></command>
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</cmdsynopsis>
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<cmdsynopsis>
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<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>
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</cmdsynopsis>
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<cmdsynopsis>
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<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>
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</cmdsynopsis>
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<cmdsynopsis>
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<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>
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</cmdsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><command>systemd-dissect</command> is a tool for introspecting and interacting with file system OS
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disk images. It supports four different operations:</para>
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<orderedlist>
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<listitem><para>Show general OS image information, including the image's
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<citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry> data,
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machine ID, partition information and more.</para></listitem>
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<listitem><para>Mount an OS image to a local directory. In this mode it will dissect the OS image and
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mount the included partitions according to their designation onto a directory and possibly
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sub-directories.</para></listitem>
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<listitem><para>Copy files and directories in and out of an OS image.</para></listitem>
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</orderedlist>
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<para>The tool may operate on three types of OS images:</para>
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<orderedlist>
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<listitem><para>OS disk images containing a GPT partition table envelope, with partitions marked
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according to the <ulink url="https://systemd.io/DISCOVERABLE_PARTITIONS">Discoverable Partitions
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Specification</ulink>.</para></listitem>
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<listitem><para>OS disk images containing just a plain file-system without an enveloping partition
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table. (This file system is assumed to be the root file system of the OS.)</para></listitem>
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<listitem><para>OS disk images containing a GPT or MBR partition table, with a single
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partition only. (This partition is assumed to contain the root file system of the OS.)</para></listitem>
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</orderedlist>
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<para>OS images may use any kind of Linux-supported file systems. In addition they may make use of LUKS
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disk encryption, and contain Verity integrity information. Note that qualifying OS images may be booted
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with <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
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<option>--image=</option> switch, and be used as root file system for system service using the
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<varname>RootImage=</varname> unit file setting, see
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<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
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<para>Note that the partition table shown when invoked without command switch (as listed below) does not
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necessarily show all partitions included in the image, but just the partitions that are understood and
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considered part of an OS disk image. Specifically, partitions of unknown types are ignored, as well as
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duplicate partitions (i.e. more than one per partition type), as are root and <filename>/usr/</filename>
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partitions of architectures not compatible with the local system. In other words: this tool will display
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what it operates with when mounting the image. To display the complete list of partitions use a tool such
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as <citerefentry
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project='man-pages'><refentrytitle>fdisk</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
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</refsect1>
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<refsect1>
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<title>Commands</title>
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<para>If neither of the command switches listed below are passed the specified disk image is opened and
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general information about the image and the contained partitions and their use is shown.</para>
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<variablelist>
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<varlistentry>
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<term><option>--mount</option></term>
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<term><option>-m</option></term>
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<listitem><para>Mount the specified OS image to the specified directory. This will dissect the image,
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determine the OS root file system — as well as possibly other partitions — and mount them to the
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specified directory. If the OS image contains multiple partitions marked with the <ulink
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url="https://systemd.io/DISCOVERABLE_PARTITIONS">Discoverable Partitions Specification</ulink>
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multiple nested mounts are established. This command expects two arguments: a path to an image file
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and a path to a directory where to mount the image.</para>
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<para>To unmount an OS image mounted like this use <citerefentry
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project='man-pages'><refentrytitle>umount</refentrytitle><manvolnum>8</manvolnum></citerefentry>'s
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<option>-R</option> switch (for recursive operation), so that the OS image and all nested partition
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mounts are unmounted.</para>
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<para>When the OS image contains LUKS encrypted or Verity integrity protected file systems
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appropriate volumes are automatically set up and marked for automatic disassembly when the image is
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unmounted.</para>
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<para>The OS image may either be specified as path to an OS image stored in a regular file or may
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refer to block device node (in the latter case the block device must be the "whole" device, i.e. not
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a partition device). (The other supported commands described here support this, too.)</para>
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<para>All mounted file systems are checked with the appropriate <citerefentry
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project='man-pages'><refentrytitle>fsck</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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implementation in automatic fixing mode, unless explicitly turned off (<option>--fsck=no</option>) or
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read-only operation is requested (<option>--read-only</option>).</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>-M</option></term>
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<listitem><para>This is a shortcut for <option>--mount --mkdir</option>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--copy-from</option></term>
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<term><option>-x</option></term>
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<listitem><para>Copies a file or directory from the specified OS image into the specified location on
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the host file system. Expects three arguments: a path to an image file, a source path (relative to
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the image's root directory) and a destination path (relative to the current working directory, or an
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absolute path, both outside of the image). If the destination path is omitted or specified as dash
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(<literal>-</literal>), the specified file is written to standard output. If the source path in the
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image file system refers to a regular file it is copied to the destination path. In this case access
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mode, extended attributes and timestamps are copied as well, but file ownership is not. If the source
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path in the image refers to a directory, it is copied to the destination path, recursively with all
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containing files and directories. In this case the file ownership is copied too.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--copy-to</option></term>
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<term><option>-a</option></term>
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<listitem><para>Copies a file or directory from the specified location in the host file system into
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the specified OS image. Expects three arguments: a path to an image file, a source path (relative to
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the current working directory, or an absolute path, both outside of the image) and a destination path
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(relative to the image's root directory). If the source path is omitted or specified as dash
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(<literal>-</literal>), the data to write is read from standard input. If the source path in the host
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file system refers to a regular file, it is copied to the destination path. In this case access mode,
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extended attributes and timestamps are copied as well, but file ownership is not. If the source path
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in the host file system refers to a directory it is copied to the destination path, recursively with
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all containing files and directories. In this case the file ownership is copied
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too.</para>
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<para>As with <option>--mount</option> file system checks are implicitly run before the copy
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operation begins.</para></listitem>
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</varlistentry>
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<xi:include href="standard-options.xml" xpointer="help" />
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<xi:include href="standard-options.xml" xpointer="version" />
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Options</title>
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<para>The following options are understood:</para>
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<variablelist>
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<varlistentry>
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<term><option>--read-only</option></term>
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<term><option>-r</option></term>
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<listitem><para>Operate in read-only mode. By default <option>--mount</option> will establish
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writable mount points. If this option is specified they are established in read-only mode
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instead.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--fsck=no</option></term>
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<listitem><para>Turn off automatic file system checking. By default when an image is accessed for
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writing (by <option>--mount</option> or <option>--copy-to</option>) the file systems contained in the
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OS image are automatically checked using the appropriate <citerefentry
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project='man-pages'><refentrytitle>fsck</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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command, in automatic fixing mode. This behavior may be switched off using
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<option>--fsck=no</option>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--growfs=no</option></term>
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<listitem><para>Turn off automatic growing of accessed file systems to their partition size, if
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marked for that in the GPT partition table. By default when an image is accessed for writing (by
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<option>--mount</option> or <option>--copy-to</option>) the file systems contained in the OS image
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are automatically grown to their partition sizes, if bit 59 in the GPT partition flags is set for
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partition types that are defined by the <ulink
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url="https://systemd.io/DISCOVERABLE_PARTITIONS">Discoverable Partitions Specification</ulink>. This
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behavior may be switched off using <option>--growfs=no</option>. File systems are grown automatically
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on access if all of the following conditions are met:</para>
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<orderedlist>
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<listitem><para>The file system is mounted writable</para></listitem>
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<listitem><para>The file system currently is smaller than the partition it is contained in (and thus can be grown)</para></listitem>
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<listitem><para>The image contains a GPT partition table</para></listitem>
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<listitem><para>The file system is stored on a partition defined by the Discoverable Partitions Specification</para></listitem>
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<listitem><para>Bit 59 of the GPT partition flags for this partition is set, as per specification</para></listitem>
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<listitem><para>The <option>--growfs=no</option> option is not passed.</para></listitem>
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</orderedlist>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--mkdir</option></term>
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<listitem><para>If combined with <option>--mount</option> the directory to mount the OS image to is
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created if it is missing. Note that the directory is not automatically removed when the disk image is
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unmounted again.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--discard=</option></term>
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<listitem><para>Takes one of <literal>disabled</literal>, <literal>loop</literal>,
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<literal>all</literal>, <literal>crypto</literal>. If <literal>disabled</literal> the image is
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accessed with empty block discarding turned off. If <literal>loop</literal> discarding is enabled if
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operating on a regular file. If <literal>crypt</literal> discarding is enabled even on encrypted file
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systems. If <literal>all</literal> discarding is unconditionally enabled.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--root-hash=</option></term>
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<term><option>--root-hash-sig=</option></term>
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<term><option>--verity-data=</option></term>
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<listitem><para>Configure various aspects of Verity data integrity for the OS image. Option
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<option>--root-hash=</option> specifies a hex-encoded top-level Verity hash to use for setting up the
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Verity integrity protection. Option <option>--root-hash-sig=</option> specifies the path to a file
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containing a PKCS#7 signature for the hash. This signature is passed to the kernel during activation,
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which will match it against signature keys available in the kernel keyring. Option
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<option>--verity-data=</option> specifies a path to a file with the Verity data to use for the OS
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image, in case it is stored in a detached file. It is recommended to embed the Verity data directly
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in the image, using the Verity mechanisms in the <ulink
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url="https://systemd.io/DISCOVERABLE_PARTITIONS">Discoverable Partitions Specification</ulink>.
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</para></listitem>
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</varlistentry>
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<xi:include href="standard-options.xml" xpointer="no-pager" />
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<xi:include href="standard-options.xml" xpointer="no-legend" />
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<xi:include href="standard-options.xml" xpointer="json" />
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Exit status</title>
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<para>On success, 0 is returned, a non-zero failure code
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otherwise.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<ulink url="https://systemd.io/DISCOVERABLE_PARTITIONS">Discoverable Partitions Specification</ulink>,
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<citerefentry project='man-pages'><refentrytitle>umount</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>fdisk</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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