systemd/man/repart.d.xml
2020-09-19 21:20:16 +02:00

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<?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" conditional='ENABLE_REPART'
xmlns:xi="http://www.w3.org/2001/XInclude">
<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 definitions may only be used to created and initialize new partitions or grow
existing ones. In the latter case it will not grow the contained files systems however; separate
mechanisms, such as
<citerefentry><refentrytitle>systemd-growfs</refentrytitle><manvolnum>8</manvolnum></citerefentry> may be
used to 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>
<row>
<entry><constant>usr</constant></entry>
<entry><filename>/usr/</filename> file system partition type appropriate for the local architecture (an alias for an architecture <filename>/usr/</filename> file system partition type listed below, e.g. <constant>usr-x86-64</constant>)</entry>
</row>
<row>
<entry><constant>usr-verity</constant></entry>
<entry>Verity data for the <filename>/usr/</filename> file system partition for the local architecture</entry>
</row>
<row>
<entry><constant>usr-secondary</constant></entry>
<entry><filename>/usr/</filename> 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>usr-secondary-verity</constant></entry>
<entry>Verity data for the <filename>/usr/</filename> file system partition of the secondary architecture</entry>
</row>
<row>
<entry><constant>usr-x86</constant></entry>
<entry><filename>/usr/</filename> file system partition for the x86 (32bit, aka i386) architecture</entry>
</row>
<row>
<entry><constant>usr-x86-verity</constant></entry>
<entry>Verity data for the x86 (32bit) <filename>/usr/</filename> file system partition</entry>
</row>
<row>
<entry><constant>usr-x86-64</constant></entry>
<entry><filename>/usr/</filename> file system partition for the x86_64 (64bit, aka amd64) architecture</entry>
</row>
<row>
<entry><constant>usr-x86-64-verity</constant></entry>
<entry>Verity data for the x86_64 (64bit) <filename>/usr/</filename> file system partition</entry>
</row>
<row>
<entry><constant>usr-arm</constant></entry>
<entry><filename>/usr/</filename> file system partition for the ARM (32bit) architecture</entry>
</row>
<row>
<entry><constant>usr-arm-verity</constant></entry>
<entry>Verity data for the ARM (32bit) <filename>/usr/</filename> file system partition</entry>
</row>
<row>
<entry><constant>usr-arm64</constant></entry>
<entry><filename>/usr/</filename> file system partition for the ARM (64bit, aka aarch64) architecture</entry>
</row>
<row>
<entry><constant>usr-arm64-verity</constant></entry>
<entry>Verity data for the ARM (64bit, aka aarch64) <filename>/usr/</filename> file system partition</entry>
</row>
<row>
<entry><constant>usr-ia64</constant></entry>
<entry><filename>/usr/</filename> file system partition for the ia64 architecture</entry>
</row>
<row>
<entry><constant>usr-ia64-verity</constant></entry>
<entry>Verity data for the ia64 <filename>/usr/</filename> 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. Simple specifier expansion is supported, see below.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>UUID=</varname></term>
<listitem><para>The UUID 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 UUID 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
all-zero UUID set. If not specified a UUID 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 a minimum size constraint of 10M and no maximum size
constraint is set.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>PaddingMinBytes=</varname></term>
<term><varname>PaddingMaxBytes=</varname></term>
<listitem><para>Specifies minimum and maximum size constraints 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>CopyBlocks=</varname></term>
<listitem><para>Takes a path to a regular file, block device node or directory. If specified and the
partition is newly created the data from the specified path is written to the newly created
partition, on the block level. If a directory is specified the backing block device of the file
system the directory is on is determined and the data read directly from that. This option is useful
to efficiently replicate existing file systems on the block level on a new partition, for example to
build a simple OS installer or OS image builder.</para>
<para>The file specified here must have a size that is a multiple of the basic block size 512 and not
be empty. If this option is used, the size allocation algorithm is slightly altered: the partition is
created as least as big as required to fit the data in, i.e. the data size is an additional minimum
size value taken into consideration for the allocation algorithm, similar to and in addition to the
<varname>SizeMin=</varname> value configured above.</para>
<para>This option has no effect if the partition it is declared for already exists, i.e. existing
data is never overwritten. Note that the data is copied in before the partition table is updated,
i.e. before the partition actually is persistently created. This provides robustness: it is
guaranteed that the partition either doesn't exist or exists fully populated; it is not possible that
the partition exists but is not or only partially populated.</para>
<para>This option cannot be combined with <varname>Format=</varname> or
<varname>CopyFiles=</varname>.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>Format=</varname></term>
<listitem><para>Takes a file system name, such as <literal>ext4</literal>, <literal>btrfs</literal>,
<literal>xfs</literal> or <literal>vfat</literal>, or the special value <literal>swap</literal>. If
specified and the partition is newly created it is formatted with the specified file system (or as
swap device). The file system UUID and label are automatically derived from the partition UUID and
label. If this option is used, the size allocation algorithm is slightly altered: the partition is
created as least as big as required for the minimal file system of the specified type (or 4KiB if the
minimal size is not known).</para>
<para>This option has no effect if the partition already exists.</para>
<para>Similar to the behaviour of <varname>CopyBlocks=</varname> the file system is formatted before
the partition is created, ensuring that the partition only ever exists with a fully initialized
file system.</para>
<para>This option cannot be combined with <varname>CopyBlocks=</varname>.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>CopyFiles=</varname></term>
<listitem><para>Takes a pair of colon separated absolute file system paths. The first path refers to
a source file or directory on the host, the second path refers to a target in the file system of the
newly created partition and formatted file system. This setting may be used to copy files or
directories from the host into the file system that is created due to the <varname>Format=</varname>
option. If <varname>CopyFiles=</varname> is used without <varname>Format=</varname> specified
explicitly, <literal>Format=</literal> with a suitable default is implied (currently
<literal>ext4</literal>, but this may change in the future). This option may be used multiple times
to copy multiple files or directories from host into the newly formatted file system. The colon and
second path may be omitted in which case the source path is also used as the target path (relative to
the root of the newly created file system). If the source path refers to a directory it is copied
recursively.</para>
<para>This option has no effect if the partition already exists: it cannot be used to copy additional
files into an existing partition, it may only be used to populate a file system created anew.</para>
<para>The copy operation is executed before the file system is registered in the partition table,
thus ensuring that a file system populated this way only ever exists fully initialized.</para>
<para>This option cannot be combined with <varname>CopyBlocks=</varname>.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>Encrypt=</varname></term>
<listitem><para>Takes a boolean parameter, defaulting to false. If true the partition will be
formatted with a LUKS2 superblock, before the blocks configured with <varname>CopyBlocks=</varname>
are copied in or the file system configured with <varname>Format=</varname> is created.</para>
<para>The LUKS2 UUID is automatically derived from the partition UUID in a stable fashion. A single
key is added to the LUKS2 superblock, configurable with the <option>--key-file=</option> switch to
<command>systemd-repart</command>.</para>
<para>When used this slightly alters the size allocation logic as the implicit, minimal size limits
of <varname>Format=</varname> and <varname>CopyBlocks=</varname> are increased by the space necessary
for the LUKS2 superblock (see above).</para>
<para>This option has no effect if the partition already exists.</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>Specifiers</title>
<para>Specifiers may be used in the <varname>Label=</varname> setting. The following expansions are understood:</para>
<table class='specifiers'>
<title>Specifiers available</title>
<tgroup cols='3' align='left' colsep='1' rowsep='1'>
<colspec colname="spec" />
<colspec colname="mean" />
<colspec colname="detail" />
<thead>
<row>
<entry>Specifier</entry>
<entry>Meaning</entry>
<entry>Details</entry>
</row>
</thead>
<tbody>
<xi:include href="standard-specifiers.xml" xpointer="a"/>
<xi:include href="standard-specifiers.xml" xpointer="b"/>
<xi:include href="standard-specifiers.xml" xpointer="B"/>
<xi:include href="standard-specifiers.xml" xpointer="H"/>
<xi:include href="standard-specifiers.xml" xpointer="l"/>
<xi:include href="standard-specifiers.xml" xpointer="m"/>
<xi:include href="standard-specifiers.xml" xpointer="o"/>
<xi:include href="standard-specifiers.xml" xpointer="v"/>
<xi:include href="standard-specifiers.xml" xpointer="w"/>
<xi:include href="standard-specifiers.xml" xpointer="W"/>
<xi:include href="standard-specifiers.xml" xpointer="percent"/>
</tbody>
</tgroup>
</table>
</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>