man: document systemd-repart

4 files changed, 660 insertions, 0 deletions

diff --git a/man/repart.d.xml b/man/repart.d.xml
new file mode 100644
index 0000000000..2fe74193d3
--- /dev/null
+++ b/man/repart.d.xml
@@ -0,0 +1,388 @@
+<?xml version='1.0'?>
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+<refentry id="repart.d">
+
+  <refentryinfo>
+    <title>repart.d</title>
+    <productname>systemd</productname>
+  </refentryinfo>
+
+  <refmeta>
+    <refentrytitle>repart.d</refentrytitle>
+    <manvolnum>5</manvolnum>
+  </refmeta>
+
+  <refnamediv>
+    <refname>repart.d</refname>
+    <refpurpose>Partition Definition Files for Automatic Boot-Time Repartitioning</refpurpose>
+  </refnamediv>
+
+  <refsynopsisdiv>
+    <para><literallayout><filename>/etc/repart.d/*.conf</filename>
+<filename>/run/repart.d/*.conf</filename>
+<filename>/usr/lib/repart.d/*.conf</filename>
+    </literallayout></para>
+  </refsynopsisdiv>
+
+  <refsect1>
+    <title>Description</title>
+
+    <para><filename>repart.d/*.conf</filename> files describe basic properties of partitions of block
+    devices of the local system. They may be used to declare types, names and sizes of partitions that shall
+    exist. The
+    <citerefentry><refentrytitle>systemd-repart</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+    service reads these files and attempts to add new partitions currently missing and enlarge existing
+    partitions according to these definitions. Operation is generally incremental, i.e. when applied, what
+    exists already is left intact, and partitions are never shrunk, moved or deleted.</para>
+
+    <para>These definition files are useful for implementing operating system images that are prepared and
+    delivered with minimally sized images (for example lacking any state or swap partitions), and which on
+    first boot automatically take possession of any remaining disk space following a few basic rules.</para>
+
+    <para>Currently, support for partition definition files is only implemented for GPT partitition
+    tables.</para>
+
+    <para>Partition files are generally matched against any partitions already existing on disk in a simple
+    algorithm: the partition files are sorted by their filename (ignoring the directory prefix), and then
+    compared in order against existing partitions matching the same partition type UUID. Specifically, the
+    first existing partition with a specific partition type UUID is assigned the first definition file with
+    the same partition type UUID, and the second existing partition with a specific type UUID the second
+    partition file with the same type UUID, and so on. Any left-over partition files that have no matching
+    existing partition are assumed to define new partition that shall be created. Such partitions are
+    appended to the end of the partition table, in the order defined by their names utilizing the first
+    partition slot greater than the highest slot number currently in use. Any existing partitions that have
+    no matching partition file are left as they are.</para>
+
+    <para>Note that these partition definition files do not describe the contents of the partitions, such as
+    the file system used. Separate mechanisms, such as
+    <citerefentry><refentrytitle>systemd-growfs</refentrytitle><manvolnum>8</manvolnum></citerefentry> and
+    <command>systemd-makefs</command> maybe be used to initialize or grow the file systems inside of these
+    partitions.</para>
+  </refsect1>
+
+  <refsect1>
+    <title>[Partition] Section Options</title>
+
+    <variablelist>
+      <varlistentry>
+        <term><varname>Type=</varname></term>
+
+        <listitem><para>The GPT partition type UUID to match. This may be a GPT partition type UUID such as
+        <constant>4f68bce3-e8cd-4db1-96e7-fbcaf984b709</constant>, or one of the following special
+        identifiers:</para>
+
+        <table>
+          <title>GPT partition type identifiers</title>
+
+          <tgroup cols='2' align='left' colsep='1' rowsep='1'>
+            <colspec colname="name" />
+            <colspec colname="explanation" />
+
+            <thead>
+              <row>
+                <entry>Identifier</entry>
+                <entry>Explanation</entry>
+              </row>
+            </thead>
+
+            <tbody>
+              <row>
+                <entry><constant>esp</constant></entry>
+                <entry>EFI System Partition</entry>
+              </row>
+
+              <row>
+                <entry><constant>xbootldr</constant></entry>
+                <entry>Extended Boot Loader Partition</entry>
+              </row>
+
+              <row>
+                <entry><constant>swap</constant></entry>
+                <entry>Swap partition</entry>
+              </row>
+
+              <row>
+                <entry><constant>home</constant></entry>
+                <entry>Home (<filename>/home/</filename>) partition</entry>
+              </row>
+
+              <row>
+                <entry><constant>srv</constant></entry>
+                <entry>Server data (<filename>/srv/</filename>) partition</entry>
+              </row>
+
+              <row>
+                <entry><constant>var</constant></entry>
+                <entry>Variable data (<filename>/var/</filename>) partition</entry>
+              </row>
+
+              <row>
+                <entry><constant>tmp</constant></entry>
+                <entry>Temporary data (<filename>/var/tmp/</filename>) partition</entry>
+              </row>
+
+              <row>
+                <entry><constant>linux-generic</constant></entry>
+                <entry>Generic Linux file system partition</entry>
+              </row>
+
+              <row>
+                <entry><constant>root</constant></entry>
+                <entry>Root file system partition type appropriate for the local architecture (an alias for an architecture root file system partition type listed below, e.g. <constant>root-x86-64</constant>)</entry>
+              </row>
+
+              <row>
+                <entry><constant>root-verity</constant></entry>
+                <entry>Verity data for the root file system partition for the local architecture</entry>
+              </row>
+
+              <row>
+                <entry><constant>root-secondary</constant></entry>
+                <entry>Root file system partition of the secondary architecture of the local architecture; usually the matching 32bit architecture for the local 64bit architecture)</entry>
+              </row>
+
+              <row>
+                <entry><constant>root-secondary-verity</constant></entry>
+                <entry>Verity data for the root file system partition of the secondary architecture</entry>
+              </row>
+
+              <row>
+                <entry><constant>root-x86</constant></entry>
+                <entry>Root file system partition for the x86 (32bit, aka i386) architecture</entry>
+              </row>
+
+              <row>
+                <entry><constant>root-x86-verity</constant></entry>
+                <entry>Verity data for the x86 (32bit) root file system partition</entry>
+              </row>
+
+              <row>
+                <entry><constant>root-x86-64</constant></entry>
+                <entry>Root file system partition for the x86_64 (64bit, aka amd64) architecture</entry>
+              </row>
+
+              <row>
+                <entry><constant>root-x86-64-verity</constant></entry>
+                <entry>Verity data for the x86_64 (64bit) root file system partition</entry>
+              </row>
+
+              <row>
+                <entry><constant>root-arm</constant></entry>
+                <entry>Root file system partition for the ARM (32bit) architecture</entry>
+              </row>
+
+              <row>
+                <entry><constant>root-arm-verity</constant></entry>
+                <entry>Verity data for the ARM (32bit) root file system partition</entry>
+              </row>
+
+              <row>
+                <entry><constant>root-arm64</constant></entry>
+                <entry>Root file system partition for the ARM (64bit, aka aarch64) architecture</entry>
+              </row>
+
+              <row>
+                <entry><constant>root-arm64-verity</constant></entry>
+                <entry>Verity data for the ARM (64bit, aka aarch64) root file system partition</entry>
+              </row>
+
+              <row>
+                <entry><constant>root-ia64</constant></entry>
+                <entry>Root file system partition for the ia64 architecture</entry>
+              </row>
+
+              <row>
+                <entry><constant>root-ia64-verity</constant></entry>
+                <entry>Verity data for the ia64 root file system partition</entry>
+              </row>
+            </tbody>
+          </tgroup>
+        </table>
+
+        <para>This setting defaults to <constant>linux-generic</constant>.</para>
+
+        <para>Most of the partition type UUIDs listed above are defined in the <ulink
+        url="https://systemd.io/DISCOVERABLE_PARTITIONS">Discoverable Partitions
+        Specification</ulink>.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>Label=</varname></term>
+
+        <listitem><para>The textual label to assign to the partition if none is assigned yet. Note that this
+        setting is not used for matching. It is also not used when a label is already set for an existing
+        partition. It is thus only used when a partition is newly created or when an existing one had a no
+        label set (that is: an empty label). If not specified a label derived from the partition type is
+        automatically used.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>Priority=</varname></term>
+
+        <listitem><para>A numeric priority to assign to this partition, in the range -2147483648…2147483647,
+        with smaller values indicating higher priority, and higher values indicating smaller priority. This
+        priority is used in case the configured size constraints on the defined partitions do not permit
+        fitting all partitions onto the available disk space. If the partitions do not fit, the highest
+        numeric partition priority of all defined partitions is determined, and all defined partitions with
+        this priority are removed from the list of new partitions to create (which may be multiple, if the
+        same priority is used for multiple partitions). The fitting algorithm is then tried again. If the
+        partitions still do not fit, the now highest numeric partition priority is determined, and the
+        matching partitions removed too, and so on. Partitions of a priority of 0 or lower are never
+        removed. If all partitions with a priority above 0 are removed and the partitions still do not fit on
+        the device the operation fails. Note that this priority has no effect on ordering partitions, for
+        that use the alphabetical order of the filenames of the partition definition files. Defaults to
+        0.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>Weight=</varname></term>
+
+        <listitem><para>A numeric weight to assign to this partition in the range 0…1000000. Available disk
+        space is assigned the defined partitions according to their relative weights (subject to the size
+        constraints configured with <varname>SizeMinBytes=</varname>, <varname>SizeMaxBytes=</varname>), so
+        that a partition with weight 2000 gets double the space as one with weight 1000, and a partition with
+        weight 333 a third of that. Defaults to 1000.</para>
+
+        <para>The <varname>Weight=</varname> setting is used to distribute available disk space in an
+        "elastic" fashion, based on the disk size and existing partitions. If a partition shall have a fixed
+        size use both <varname>SizeMinBytes=</varname> and <varname>SizeMaxBytes=</varname> with the same
+        value in order to fixate the size to one value, in which case the weight has no
+        effect.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>PaddingWeight=</varname></term>
+
+        <listitem><para>Similar to <varname>Weight=</varname> but sets a weight for the free space after the
+        partition (the "padding"). When distributing available space the weights of all partitions and all
+        defined padding is summed, and then each partition and padding gets the fraction defined by its
+        weight. Defaults to 0, i.e. by default no padding is applied.</para>
+
+        <para>Padding is useful if empty space shall be left for later additions or a safety margin at the
+        end of the device or between partitions.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>SizeMinBytes=</varname></term>
+        <term><varname>SizeMaxBytes=</varname></term>
+
+        <listitem><para>Specifies minimum and maximum size constraints in bytes. Takes the usual K, M, G, T,
+        …  suffixes (to the base of 1024). If <varname>SizeMinBytes=</varname> is specified the partition is
+        created at or grown to at least the specified size. If <varname>SizeMaxBytes=</varname> is specified
+        the partition is created at or grown to at most the specified size. The precise size is determined
+        through the weight value value configured with <varname>Weight=</varname>, see above. When
+        <varname>SizeMinBytes=</varname> is set equal to <varname>SizeMaxBytes=</varname> the configured
+        weight has no effect as the partition is explicitly sized to the specified fixed value. Note that
+        partitions are never created smaller than 4096 bytes, and since partitions are never shrunk the
+        previous size of the partition (in case the partition already exists) is also enforced as lower bound
+        for the new size. The values should be specified as multiples of 4096 bytes, and are rounded upwards
+        (in case of <varname>SizeMinBytes=</varname>) or downwards (in case of
+        <varname>SizeMaxBytes=</varname>) otherwise. If the backing device does not provide enough space to
+        fulfill the constraints placing the partition will fail. For partitions that shall be created,
+        depending on the setting of <varname>Priority=</varname> (see above) the partition might be dropped
+        and the placing algorithm restarted. By default no size constraints are set.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>PaddingMinBytes=</varname></term>
+        <term><varname>PaddingMaxBytes=</varname></term>
+
+        <listitem><para>Specifies minimum and maximum size constrains in bytes for the free space after the
+        partition (the "padding"). Semantics are similar to <varname>SizeMinBytes=</varname> and
+        <varname>SizeMaxBytes=</varname>, except that unlike partition sizes free space can be shrunk and can
+        be as small as zero. By default no size constraints on padding are set, so that only
+        <varname>PaddingWeight=</varname> determines the size of the padding applied.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>FactoryReset=</varname></term>
+
+        <listitem><para>Takes a boolean argument. If specified the partition is marked for removal during a
+        factory reset operation. This functionality is useful to implement schemes where images can be reset
+        into their original state by removing partitions and creating them anew. Defaults to off.</para></listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+
+  <refsect1>
+    <title>Examples</title>
+
+    <example>
+      <title>Grow the root partition to the full disk size at first boot</title>
+
+      <para>With the following file the root partition is automatically grown to the full disk if possible during boot.</para>
+
+      <para><programlisting># /usr/lib/repart.d/50-root.conf
+[Partition]
+Type=root
+</programlisting></para>
+    </example>
+
+    <example>
+      <title>Create a swap and home partition automatically on boot, if missing</title>
+
+      <para>The home partition gets all available disk space while the swap partition gets 1G at most and 64M
+      at least. We set a priority > 0 on the swap partition to ensure the swap partition is not used if not
+      enough space is available. For every three bytes assigned to the home partition the swap partition gets
+      assigned one.</para>
+
+      <para><programlisting># /usr/lib/repart.d/60-home.conf
+[Partition]
+Type=home
+</programlisting></para>
+
+      <para><programlisting># /usr/lib/repart.d/70-swap.conf
+[Partition]
+Type=swap
+SizeMinBytes=64M
+SizeMaxBytes=1G
+Priority=1
+Weight=333
+</programlisting></para>
+    </example>
+
+    <example>
+      <title>Create B partitions in an A/B Verity setup, if missing</title>
+
+      <para>Let's say the vendor intends to update OS images in an A/B setup, i.e. with two root partitions
+      (and two matching Verity partitions) that shall be used alternatingly during upgrades. To minimize
+      image sizes the original image is shipped only with one root and one Verity partition (the "A" set),
+      and the second root and Verity partitions (the "B" set) shall be created on first boot on the free
+      space on the medium.</para>
+
+      <para><programlisting># /usr/lib/repart.d/50-root.conf
+[Partition]
+Type=root
+SizeMinBytes=512M
+SizeMaxBytes=512M
+</programlisting></para>
+
+      <para><programlisting># /usr/lib/repart.d/60-root-verity.conf
+[Partition]
+Type=root-verity
+SizeMinBytes=64M
+SizeMaxBytes=64M
+</programlisting></para>
+
+      <para>The definitions above cover the "A" set of root partition (of a fixed 512M size) and Verity
+      partition for the root partition (of a fixed 64M size). Let's use symlinks to create the "B" set of
+      partitions, since after all they shall have the same properties and sizes as the "A" set.</para>
+
+<para><programlisting># ln -s 50-root.conf /usr/lib/repart.d/70-root-b.conf
+# ln -s 60-root-verity.conf /usr/lib/repart.d/80-root-verity-b.conf
+</programlisting></para>
+    </example>
+
+  </refsect1>
+
+  <refsect1>
+    <title>See Also</title>
+    <para>
+      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>systemd-repart</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+      <citerefentry project='man-pages'><refentrytitle>sfdisk</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+    </para>
+  </refsect1>
+
+</refentry>
diff --git a/man/rules/meson.build b/man/rules/meson.build
index 90376da775..3dc0a045a7 100644
--- a/man/rules/meson.build
+++ b/man/rules/meson.build
@@ -47,6 +47,7 @@ manpages = [
  ['pam_systemd', '8', [], 'HAVE_PAM'],
  ['portablectl', '1', [], 'ENABLE_PORTABLED'],
  ['pstore.conf', '5', ['pstore.conf.d'], 'ENABLE_PSTORE'],
+ ['repart.d', '5', [], ''],
  ['resolvectl', '1', ['resolvconf'], 'ENABLE_RESOLVE'],
  ['resolved.conf', '5', ['resolved.conf.d'], 'ENABLE_RESOLVE'],
  ['runlevel', '8', [], ''],
@@ -769,6 +770,7 @@ manpages = [
   'ENABLE_RANDOMSEED'],
  ['systemd-rc-local-generator', '8', [], ''],
  ['systemd-remount-fs.service', '8', ['systemd-remount-fs'], ''],
+ ['systemd-repart', '8', ['systemd-repart.service'], ''],
  ['systemd-resolved.service', '8', ['systemd-resolved'], 'ENABLE_RESOLVE'],
  ['systemd-rfkill.service',
   '8',
diff --git a/man/systemd-makefs@.service.xml b/man/systemd-makefs@.service.xml
index 8514af67bc..d07d90315a 100644
--- a/man/systemd-makefs@.service.xml
+++ b/man/systemd-makefs@.service.xml
@@ -80,6 +80,7 @@
       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>systemd-repart</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
       <citerefentry project='man-pages'><refentrytitle>mkfs.btrfs</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
       <citerefentry project='man-pages'><refentrytitle>mkfs.cramfs</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
       <citerefentry project='man-pages'><refentrytitle>mkfs.ext4</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
diff --git a/man/systemd-repart.xml b/man/systemd-repart.xml
new file mode 100644
index 0000000000..cffcb5403a
--- /dev/null
+++ b/man/systemd-repart.xml
@@ -0,0 +1,269 @@
+<?xml version='1.0'?> <!--*-nxml-*-->
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+<!-- SPDX-License-Identifier: LGPL-2.1+ -->
+
+<refentry id="systemd-repart"
+    xmlns:xi="http://www.w3.org/2001/XInclude">
+
+  <refentryinfo>
+    <title>systemd-repart</title>
+    <productname>systemd</productname>
+  </refentryinfo>
+
+  <refmeta>
+    <refentrytitle>systemd-repart</refentrytitle>
+    <manvolnum>8</manvolnum>
+  </refmeta>
+
+  <refnamediv>
+    <refname>systemd-repart</refname>
+    <refname>systemd-repart.service</refname>
+    <refpurpose>Automatically grow and add partitions</refpurpose>
+  </refnamediv>
+
+  <refsynopsisdiv>
+    <cmdsynopsis>
+      <command>systemd-repart</command>
+      <arg choice="opt" rep="repeat">OPTIONS</arg>
+      <arg choice="opt" rep="repeat"><replaceable><optional>BLOCKDEVICE</optional></replaceable></arg>
+    </cmdsynopsis>
+
+    <para><filename>systemd-repart.service</filename></para>
+  </refsynopsisdiv>
+
+  <refsect1>
+    <title>Description</title>
+
+    <para><command>systemd-repart</command> grows and adds partitions to a partition table, based on the
+    configuration files described in
+    <citerefentry><refentrytitle>repart.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
+    </para>
+
+    <para>If invoked with no arguments, it operates on the block device backing the root file system partition
+    of the OS, thus growing and adding partitions of the booted OS image itself. When called in the initial
+    RAM disk it operates on the block device backing <filename>/sysroot/</filename> instead, i.e. on the
+    block device the system will soon transition into. The <filename>systemd-repart.service</filename>
+    service is generally run at boot in the initial RAM disk, in order to augment the partition table of the
+    OS before its partitions are mounted. <command>systemd-repart</command> (mostly) operates in a purely
+    incremental mode: it only grows existing and adds new partitions; it does not shrink, delete or move
+    existing partitions. The service is intended to be run on every boot, but when it detects that the
+    partition table already matches the installed <filename>repart.d/*.conf</filename> configuration
+    files, it executes no operation.</para>
+
+    <para><command>systemd-repart</command> is intended to be used when deploying OS images, to automatically
+    adjust them to the system they are running on, during first boot. This way the deployed image can be
+    minimal in size and may be augmented automatically at boot when needed, taking possession of disk space
+    available but not yet used. Specifically the following use cases are among those covered:</para>
+
+    <itemizedlist>
+      <listitem><para>The root partition may be grown to cover the whole available disk space</para></listitem>
+      <listitem><para>A <filename>/home/</filename>, swap or <filename>/srv</filename> partition can be added in</para></listitem>
+      <listitem><para>A second (or third, …) root partition may be added in, to cover A/B style setups
+      where a second version of the root file system is alternatingly used for implementing update
+      schemes. The deployed image would carry only a single partition ("A") but on first boot a second
+      partition ("B") for this purpose is automatically created.</para></listitem>
+    </itemizedlist>
+
+    <para>The algorithm executed by <command>systemd-repart</command> is roughly as follows:</para>
+
+    <orderedlist>
+      <listitem><para>The <filename>repart.d/*.conf</filename> configuration files are loaded and parsed,
+      and ordered by filename (without the directory suffix). </para></listitem>
+
+      <listitem><para>The partition table already existing on the block device is loaded and
+      parsed.</para></listitem>
+
+      <listitem><para>The existing partitions in the partition table are matched up with the
+      <filename>repart.d/*.conf</filename> files by GPT partition type UUID. The first existing partition
+      of a specific type is assigned the first configuration file declaring the same type. The second
+      existing partition of a specific type is then assigned the second configuration file declaring the same
+      type, and so on. After this iterative assigning is complete any left-over existing partitions that have
+      no matching configuration file are considered "foreign" and left as they are. And any configuration
+      files for which no partition currently exists are understood as a request to create such a
+      partition.</para></listitem>
+
+      <listitem><para>Taking the size constraints and weights declared in the configuration files into
+      account, all partitions that shall be created are now allocated to the disk, taking up all free space,
+      always respecting the size and padding requests. Similar, existing partitions that are determined to
+      grow are grown. New partitions are always appended to the end of the existing partition table, taking
+      the first partition table slot whose index is greater than the indexes of all existing
+      partitions. Partition table slots are never reordered and thus partition numbers are ensured to remain
+      stable. Note that this allocation happens in RAM only, the partition table on disk is not updated
+      yet.</para></listitem>
+
+      <listitem><para>All existing partitions for which configuration files exist and which currently have no
+      GPT partition label set will be assigned a label, either explicitly configured in the configuration or
+      (if that's missing) derived automatically from the partition type. The same is done for all partitions
+      that are newly created. These assignments are done in RAM only, too, the disk is not updated
+      yet.</para></listitem>
+
+      <listitem><para>Similarly, all existing partitions for which configuration files exist and which
+      currently have an all-zero identifying UUID will be assigned a new UUID. This UUID is cryptographically
+      hashed from a common seed value together with the partition type UUID (and a counter in case multiple
+      partitions of the same type are defined), see below. The same is done for all partitions that are
+      created anew. These assignments are done in RAM only, too, the disk is not updated
+      yet.</para></listitem>
+
+      <listitem><para>Similarly, if the disk's volume UUID is all zeroes it is also initialized, also
+      cryptographically hashed from the same common seed value. Also, in RAM only, too.</para></listitem>
+
+      <listitem><para>The disk space assigned to new partitions (i.e. what was previously considered free
+      space but is no longer) is now erased. Specifically, all file system signatures are removed, and if the
+      device supports it the <constant>BLKDISCARD</constant> I/O control command is issued to inform the
+      hardware that the space is empty now. In addition any "padding" between partitions and at the end of
+      the device is similarly erased.</para></listitem>
+
+      <listitem><para>The new partition table is finally written to disk. The kernel is asked to reread the
+      partition table.</para></listitem>
+    </orderedlist>
+
+    <para>As exception to the normally strictly incremental operation, when called in a special "factory
+    reset" mode <command>systemd-repart</command> may also be used to erase select existing partitions to
+    reset an installation back to vendor defaults. This mode of operation is used when either the
+    <option>--factory-reset=yes</option> switch is passed on the tool's command line, or the
+    <option>systemd.factory_reset=yes</option> option specified on the kernel command line, or the
+    <varname>FactoryReset</varname> EFI variable (vendor UUID
+    <constant>8cf2644b-4b0b-428f-9387-6d876050dc67</constant>) is set to "yes". It alters the algorithm above
+    slightly: between the 3rd and the 4th step above the any partition marked explicitly via the
+    <varname>FactoryReset=</varname> boolean is deleted, and the algorithm restarted, thus immediately
+    re-creating these partitions anew empty.</para>
+
+    <para>Note that <command>systemd-repart</command> only changes partition tables, it does not create or
+    resize any file systems within these partitions. A separate mechanism should be used for that, for
+    example
+    <citerefentry><refentrytitle>systemd-growfs</refentrytitle><manvolnum>8</manvolnum></citerefentry> and
+    <command>systemd-makefs</command>.</para>
+
+    <para>The UUIDs identifying the new partitions created (or assigned to existing partitions that have no
+    UUID yet), as well as the disk as a whole are hashed cryptographically from a common seed value. This
+    seed value is usually the
+    <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry> of the
+    system, so that the machine ID reproducibly determines the UUIDs assigned to all partitions. If the
+    machine ID cannot be read (or the user passes <option>--seed=random</option>, see below) the seed is
+    generated randomly instead, so that the partition UUIDs are also effectively random. The seed value may
+    also be set explicitly, formatted as UUID via the <option>--seed=</option> option. By hashing these UUIDs
+    from a common seed images prepared with this tool become reproducible and the result of the algorithm
+    above deterministic.</para>
+  </refsect1>
+
+  <refsect1>
+    <title>Options</title>
+
+    <para>The following options are understood:</para>
+
+    <variablelist>
+      <varlistentry>
+        <term><option>--dry-run=</option></term>
+        <listitem><para>Takes a boolean. If this switch is not specified <option>--dry-run=yes</option> is
+        the implied default. Controls whether <filename>systemd-repart</filename> executes the requested
+        re-partition operations or whether it should only show what it would do. Unless
+        <option>--dry-run=no</option> is specified <filename>systemd-repart</filename> will not actually
+        touch the device's partition table.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><option>--empty=</option></term>
+        <listitem><para>Takes one of <literal>refuse</literal>, <literal>allow</literal>,
+        <literal>require</literal> or <literal>force</literal>. Controls how to operate on block devices that
+        are entirely empty, i.e. carry no partition table/disk label yet. If this switch is not specified the
+        implied default is <literal>refuse</literal>.</para>
+
+        <para>If <literal>refuse</literal> <command>systemd-repart</command> requires that the block device
+        it shall operate on already carries a partition table and refuses operation if none is found. If
+        <literal>allow</literal> the command will extend an existing partition table or create a new one if
+        none exists. If <literal>require</literal> the command will create a new partition table if none
+        exists so far, and refuse operation if one already exists. If <literal>force</literal> it will create
+        a fresh partition table unconditionally, erasing the disk fully in effect. If
+        <literal>force</literal> no existing partitions will be taken into account or survive the
+        operation. Hence: use with care, this is a great way to lose all your data.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><option>--discard=</option></term>
+
+        <listitem><para>Takes a boolean. If this switch is not specified <option>--discard=yes</option> is
+        the implied default. Controls whether to issue the <constant>BLKDISCARD</constant> I/O control
+        command on the space taken up by any added partitions or on the space in between them. Usually, it's
+        a good idea to issue this request since it tells the underlying hardware that the covered blocks
+        shall be considered empty, improving performance.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><option>--factory-reset=</option></term>
+
+        <listitem><para>Takes boolean. If this switch is not specified <option>--factory=reset=no</option> is
+        the implied default. Controls whether to operate in "factory reset" mode, see above. If set to true
+        this will remove all existing partitions marked with <varname>FactoryReset=</varname> set to yes
+        early while executing the re-partitioning algorithm. Use with care, this is a great way to lose all
+        your data. Note that partition files need to explicitly turn <varname>FactoryReset=</varname> on, as
+        the option defaults to off. If no partitions are marked for factory reset this switch has no
+        effect. Note that there are two other methods to request factory reset operation: via the kernel
+        command line and via an EFI variable, see above.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><option>--can-factory-reset</option></term>
+
+        <listitem><para>If this switch is specified the disk is not re-partitioned. Instead it is determined
+        if any existing partitions are marked with <varname>FactoryReset=</varname>. If there are the tool
+        will exit with exit status zero, otherwise non-zero. This switch may be used to quickly determine
+        whether the running system supports a factory reset mechanism built on
+        <command>systemd-repart</command>.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><option>--root=</option></term>
+
+        <listitem><para>Takes a path to a directory to use as root file system when searching for
+        <filename>repart.d/*.conf</filename> files and for the machine ID file to use as seed. By default
+        when invoked on the regular system this defaults to the host's root file system
+        <filename>/</filename>. If invoked from the initial RAM disk this defaults to
+        <filename>/sysroot/</filename>, so that the tool operates on the configuration and machine ID stored
+        in the root file system later transitioned into itself.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><option>--seed=</option></term>
+
+        <listitem><para>Takes a UUID as argument or the special value <constant>random</constant>. If a UUID
+        is specified the UUIDs to assign to partitions and the partition table itself are derived via
+        cryptographic hashing from it. If not specified it is attempted to read the machine ID from the host
+        (or more precisely, the root directory configured via <option>--root=</option>) and use it as seed
+        instead, falling back to a randomized seed otherwise. Use <option>--seed=random</option> to force a
+        randomized seed. Explicitly specifying the seed may be used to generated strictly reproducible
+        partition tables.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><option>--pretty=</option></term>
+
+        <listitem><para>Takes a boolean argument. If this switch is not specified, it defaults to on when
+        called from an interactive terminal and off otherwise. Controls whether to show a user friendly table
+        and graphic illustrating the changes applied.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><option>--definitions=</option></term>
+
+        <listitem><para>Takes a file system path. If specified the <filename>*.conf</filename> are directly
+        read from the specified directory instead of searching in
+        <filename>/usr/lib/repart.d/*.conf</filename>, <filename>/etc/repart.d/*.conf</filename>,
+        <filename>/run/repart.d/*.conf</filename>.</para></listitem>
+      </varlistentry>
+
+      <xi:include href="standard-options.xml" xpointer="help" />
+      <xi:include href="standard-options.xml" xpointer="version" />
+    </variablelist>
+  </refsect1>
+
+  <refsect1>
+    <title>See Also</title>
+    <para>
+      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>repart.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+    </para>
+  </refsect1>
+
+</refentry>