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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> |