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diff --git a/man/systemd-gpt-auto-generator.xml b/man/systemd-gpt-auto-generator.xml new file mode 100644 index 0000000..9ac9c24 --- /dev/null +++ b/man/systemd-gpt-auto-generator.xml @@ -0,0 +1,283 @@ +<?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-or-later --> + +<refentry id="systemd-gpt-auto-generator" conditional='HAVE_BLKID'> + + <refentryinfo> + <title>systemd-gpt-auto-generator</title> + <productname>systemd</productname> + </refentryinfo> + + <refmeta> + <refentrytitle>systemd-gpt-auto-generator</refentrytitle> + <manvolnum>8</manvolnum> + </refmeta> + + <refnamediv> + <refname>systemd-gpt-auto-generator</refname> + <refpurpose>Generator for automatically discovering and mounting root, <filename>/home/</filename>, + <filename>/srv/</filename>, <filename>/var/</filename> and <filename>/var/tmp/</filename> partitions, as + well as discovering and enabling swap partitions, based on GPT partition type GUIDs</refpurpose> + </refnamediv> + + <refsynopsisdiv> + <para><filename>/usr/lib/systemd/system-generators/systemd-gpt-auto-generator</filename></para> + </refsynopsisdiv> + + <refsect1> + <title>Description</title> + + <para><filename>systemd-gpt-auto-generator</filename> is a unit generator that automatically discovers + root, <filename>/home/</filename>, <filename>/srv/</filename>, <filename>/var/</filename>, + <filename>/var/tmp/</filename>, the EFI System Partition, the Extended Boot Loader Partition and swap + partitions and creates mount and swap units for them, based on the partition type GUIDs of GUID partition + tables (GPT), see <ulink url="https://uefi.org/specifications">UEFI Specification</ulink>, chapter 5. It + implements the <ulink url="https://systemd.io/DISCOVERABLE_PARTITIONS">Discoverable Partitions + Specification</ulink>. Note that this generator has no effect on non-GPT systems, and on specific mount + points that are directories already containing files. Also, on systems where the units are explicitly + configured (for example, listed in <citerefentry + project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>), the + units this generator creates are overridden, but additional implicit dependencies might be + created.</para> + + <para>This generator will only look for the root partition on the same physical disk where the EFI System + Partition (ESP) is located. Note that support from the boot loader is required: the EFI variable + <varname>LoaderDevicePartUUID</varname> of the <constant>4a67b082-0a4c-41cf-b6c7-440b29bb8c4f</constant> + vendor UUID is used to determine from which partition, and hence the disk from which the system was + booted. If the boot loader does not set this variable, this generator will not be able to autodetect the + root partition. See the <ulink url="https://systemd.io/BOOT_LOADER_INTERFACE">Boot Loader + Interface</ulink> for details.</para> + + <para>Similarly, this generator will only look for the other partitions on the same physical disk as the + root partition. In this case, boot loader support is not required. These partitions will not be searched + for on systems where the root file system is distributed on multiple disks, for example via btrfs RAID. + </para> + + <para><filename>systemd-gpt-auto-generator</filename> is useful for centralizing file system + configuration in the partition table and making configuration in <filename>/etc/fstab</filename> or on + the kernel command line unnecessary.</para> + + <para>This generator looks for the partitions based on their + partition type GUID. The following partition type GUIDs are + identified:</para> + + <table> + <title>Partition Type GUIDs</title> + <tgroup cols='3' align='left' colsep='1' rowsep='1'> + <colspec colname="guid" /> + <colspec colname="name" /> + <colspec colname="where" /> + <colspec colname="explanation" /> + <thead> + <row> + <entry>Partition Type GUID</entry> + <entry>Name</entry> + <entry>Mount Point</entry> + <entry>Explanation</entry> + </row> + </thead> + <tbody> + <row> + <entry><constant>SD_GPT_ROOT_X86_64</constant> <constant>4f68bce3-e8cd-4db1-96e7-fbcaf984b709</constant></entry> + <entry><filename>Root Partition (x86-64)</filename></entry> + <entry><filename>/</filename></entry> + <entry>The first partition with this type UUID, located on the same disk as the ESP, is used as the root file system <filename>/</filename> on AMD64 / 64-bit x86 systems.</entry> + </row> + <row> + <entry><constant>SD_GPT_ROOT_ARM64</constant> <constant>b921b045-1df0-41c3-af44-4c6f280d3fae</constant></entry> + <entry><filename>Root Partition (64-bit ARM)</filename></entry> + <entry><filename>/</filename></entry> + <entry>The first partition with this type UUID, located on the same disk as the ESP, is used as the root file system <filename>/</filename> on AArch64 / 64-bit ARM systems.</entry> + </row> + <row> + <entry> + <constant>SD_GPT_ROOT_ALPHA</constant> <constant>SD_GPT_ROOT_ARC</constant> <constant>SD_GPT_ROOT_ARM</constant> <constant>SD_GPT_ROOT_ARM64</constant> <constant>SD_GPT_ROOT_IA64</constant> <constant>SD_GPT_ROOT_LOONGARCH64</constant> <constant>SD_GPT_ROOT_MIPS</constant> <constant>SD_GPT_ROOT_MIPS64</constant> <constant>SD_GPT_ROOT_MIPS_LE</constant> <constant>SD_GPT_ROOT_MIPS64_LE</constant> <constant>SD_GPT_ROOT_PARISC</constant> <constant>SD_GPT_ROOT_PPC</constant> <constant>SD_GPT_ROOT_PPC64</constant> <constant>SD_GPT_ROOT_PPC64_LE</constant> <constant>SD_GPT_ROOT_RISCV32</constant> <constant>SD_GPT_ROOT_RISCV64</constant> <constant>SD_GPT_ROOT_S390</constant> <constant>SD_GPT_ROOT_S390X</constant> <constant>SD_GPT_ROOT_TILEGX</constant> <constant>SD_GPT_ROOT_X86</constant> <constant>SD_GPT_ROOT_X86_64</constant> <constant>SD_GPT_USR_ALPHA</constant> <constant>SD_GPT_USR_ARC</constant> <constant>SD_GPT_USR_ARM</constant> <constant>SD_GPT_USR_IA64</constant> <constant>SD_GPT_USR_LOONGARCH64</constant> <constant>SD_GPT_USR_MIPS_LE</constant> <constant>SD_GPT_USR_MIPS64_LE</constant> <constant>SD_GPT_USR_PARISC</constant> <constant>SD_GPT_USR_PPC</constant> <constant>SD_GPT_USR_PPC64</constant> <constant>SD_GPT_USR_PPC64_LE</constant> <constant>SD_GPT_USR_RISCV32</constant> <constant>SD_GPT_USR_RISCV64</constant> <constant>SD_GPT_USR_S390</constant> <constant>SD_GPT_USR_S390X</constant> <constant>SD_GPT_USR_TILEGX</constant> <constant>SD_GPT_USR_X86</constant> + </entry> + <entry>root partitions for other architectures</entry> + <entry><filename>/</filename></entry> + <entry>The first partition with the type UUID matching the architecture, located on the same disk as the ESP, is used as the root file system <filename>/</filename>. For the full list and constant values, see <ulink url="https://systemd.io/DISCOVERABLE_PARTITIONS">Discoverable Partitions Specification</ulink>.</entry> + </row> + <row> + <entry><constant>SD_GPT_HOME</constant> <constant>933ac7e1-2eb4-4f13-b844-0e14e2aef915</constant></entry> + <entry>Home Partition</entry> + <entry><filename>/home/</filename></entry> + <entry>The first partition with this type UUID on the same disk as the ESP is mounted to <filename>/home/</filename>.</entry> + </row> + <row> + <entry><constant>SD_GPT_SRV</constant> <constant>3b8f8425-20e0-4f3b-907f-1a25a76f98e8</constant></entry> + <entry>Server Data Partition</entry> + <entry><filename>/srv/</filename></entry> + <entry>The first partition with this type UUID on the same disk as the ESP is mounted to <filename>/srv/</filename>.</entry> + </row> + <row> + <entry><constant>SD_GPT_VAR</constant> <constant>4d21b016-b534-45c2-a9fb-5c16e091fd2d</constant></entry> + <entry>Variable Data Partition</entry> + <entry><filename>/var/</filename></entry> + <entry>The first partition with this type UUID on the same disk as the ESP is mounted to <filename>/var/</filename> — under the condition its partition UUID matches the first 128 bit of the HMAC-SHA256 of the GPT type uuid of this partition keyed by the machine ID of the installation stored in <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</entry> + </row> + <row> + <entry><constant>SD_GPT_TMP</constant> <constant>7ec6f557-3bc5-4aca-b293-16ef5df639d1</constant></entry> + <entry>Temporary Data Partition</entry> + <entry><filename>/var/tmp/</filename></entry> + <entry>The first partition with this type UUID on the same disk as the ESP is mounted to <filename>/var/tmp/</filename>.</entry> + </row> + <row> + <entry><constant>SD_GPT_SWAP</constant> <constant>0657fd6d-a4ab-43c4-84e5-0933c84b4f4f</constant></entry> + <entry>Swap</entry> + <entry>n/a</entry> + <entry>All partitions with this type UUID on the same disk as the ESP are used as swap.</entry> + </row> + <row> + <entry><constant>SD_GPT_ESP</constant> <constant>c12a7328-f81f-11d2-ba4b-00a0c93ec93b</constant></entry> + <entry>EFI System Partition (ESP)</entry> + <entry><filename>/efi/</filename> or <filename>/boot/</filename></entry> + <entry>The first partition with this type UUID located on the same disk as the root partition is mounted to <filename>/boot/</filename> or <filename>/efi/</filename>, see below.</entry> + </row> + <row> + <entry><constant>SD_GPT_XBOOTLDR</constant> <constant>bc13c2ff-59e6-4262-a352-b275fd6f7172</constant></entry> + <entry>Extended Boot Loader Partition</entry> + <entry><filename>/boot/</filename></entry> + <entry>The first partition with this type UUID located on the same disk as the root partition is mounted to <filename>/boot/</filename>, see below.</entry> + </row> + </tbody> + </tgroup> + </table> + + <para>This generator understands the following attribute flags for partitions:</para> + + <table> + <title>Partition Attribute Flags</title> + <tgroup cols='3' align='left' colsep='1' rowsep='1'> + <colspec colname="flag" /> + <colspec colname="where" /> + <colspec colname="explanation" /> + <thead> + <row> + <entry>Flag</entry> + <entry>Applicable to</entry> + <entry>Explanation</entry> + </row> + </thead> + <tbody> + <row> + <entry><constant>SD_GPT_FLAG_READ_ONLY</constant> <constant>0x1000000000000000</constant></entry> + <entry><filename>/</filename>, <filename>/home/</filename>, <filename>/srv/</filename>, <filename>/var/</filename>, <filename>/var/tmp/</filename>, Extended Boot Loader Partition</entry> + <entry>Partition is mounted read-only</entry> + </row> + + <row> + <entry><constant>SD_GPT_FLAG_NO_AUTO</constant> <constant>0x8000000000000000</constant></entry> + <entry><filename>/</filename>, <filename>/home/</filename>, <filename>/srv/</filename>, <filename>/var/</filename>, <filename>/var/tmp/</filename>, Extended Boot Loader Partition</entry> + <entry>Partition is not mounted automatically</entry> + </row> + + <row> + <entry><constant>SD_GPT_FLAG_NO_BLOCK_IO_PROTOCOL</constant> <constant>0x0000000000000002</constant></entry> + <entry>EFI System Partition (ESP)</entry> + <entry>Partition is not mounted automatically</entry> + </row> + </tbody> + </tgroup> + </table> + + <para>The <filename>/home/</filename>, <filename>/srv/</filename>, <filename>/var/</filename> and + <filename>/var/tmp/</filename> partitions may be encrypted in LUKS format. In this case, a device mapper + device is set up under the names <filename>/dev/mapper/home</filename>, + <filename>/dev/mapper/srv</filename>, <filename>/dev/mapper/var</filename> and + <filename>/dev/mapper/tmp</filename>. Note that this might create conflicts if the same partition is + listed in <filename>/etc/crypttab</filename> with a different device mapper device name.</para> + + <para>When systemd is running in the initrd the <filename>/</filename> partition may be encrypted in LUKS + format as well. In this case, a device mapper device is set up under the name <filename>/dev/mapper/root</filename>, + and a <filename>sysroot.mount</filename> is set up that mounts the device under <filename>/sysroot</filename>. + For more information, see <citerefentry><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry>. + </para> + + <para>The root partition can be specified by symlinking <filename>/run/systemd/volatile-root</filename> + to <filename>/dev/block/$major:$minor</filename>. This is especially useful if the root mount has been + replaced by some form of volatile file system (overlayfs). + </para> + + <para>Mount and automount units for the EFI System Partition (ESP) are generated on EFI systems. The ESP + is mounted to <filename>/boot/</filename> (except if an Extended Boot Loader partition exists, see + below), unless a mount point directory <filename>/efi/</filename> exists, in which case it is mounted + there. Since this generator creates an automount unit, the mount will only be activated on-demand, when + accessed. On systems where <filename>/boot/</filename> (or <filename>/efi/</filename> if it exists) is an + explicitly configured mount (for example, listed in <citerefentry + project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>) or where + the <filename>/boot/</filename> (or <filename>/efi/</filename>) mount point is non-empty, no mount units + are generated.</para> + + <para>If the disk contains an Extended Boot Loader partition, as defined in the <ulink + url="https://systemd.io/BOOT_LOADER_SPECIFICATION">Boot Loader Specification</ulink>, it is made + available at <filename>/boot/</filename> (by means of an automount point, similar to the ESP, see + above). If both an EFI System Partition and an Extended Boot Loader partition exist the latter is + preferably mounted to <filename>/boot/</filename>. Make sure to create both <filename>/efi/</filename> + and <filename>/boot/</filename> to ensure both partitions are mounted.</para> + + <para>When using this generator in conjunction with btrfs file + systems, make sure to set the correct default subvolumes on them, + using <command>btrfs subvolume set-default</command>.</para> + + <para><filename>systemd-gpt-auto-generator</filename> implements + <citerefentry><refentrytitle>systemd.generator</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para> + </refsect1> + + <refsect1> + <title>Kernel Command Line</title> + + <para><filename>systemd-gpt-auto-generator</filename> understands the following kernel command line + parameters:</para> + + <variablelist class='kernel-commandline-options'> + + <varlistentry> + <term><varname>systemd.gpt_auto</varname></term> + <term><varname>rd.systemd.gpt_auto</varname></term> + + <listitem><para>Those options take an optional boolean argument, and default to yes. + The generator is enabled by default, and a false value may be used to disable it + (e.g. <literal>systemd.gpt_auto=0</literal>). + </para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>root=</varname></term> + + <listitem><para>When used with the special value <literal>gpt-auto</literal>, automatic discovery of + the root partition based on the GPT partition type is enabled. Any other value disables this + generator.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>rw</varname></term> + <term><varname>ro</varname></term> + + <listitem><para>Mount the root partition read-write or read-only <emphasis>initially</emphasis>.</para> + + <para>Note that unlike most kernel command line options these settings do not override configuration + in the file system, and the file system may be remounted later. See + <citerefentry><refentrytitle>systemd-remount-fs.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>. + </para></listitem> + </varlistentry> + </variablelist> + </refsect1> + + <refsect1> + <title>See Also</title> + <para> + <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd-cryptsetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, + <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>, + <citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry project='man-pages'><refentrytitle>btrfs</refentrytitle><manvolnum>8</manvolnum></citerefentry> + </para> + </refsect1> + +</refentry> |