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| <refentry id="systemd-gpt-auto-generator"> |
| |
| <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 the EFI System |
| Partition (ESP) is located on. 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>44479540-f297-41b2-9af7-d131d5f0458a</entry> |
| <entry><filename>Root Partition (x86)</filename></entry> |
| <entry><filename>/</filename></entry> |
| <entry>On 32-bit x86 systems, the first x86 root partition on the disk the EFI ESP is located on is mounted to the root directory <filename>/</filename>.</entry> |
| </row> |
| <row> |
| <entry>4f68bce3-e8cd-4db1-96e7-fbcaf984b709</entry> |
| <entry><filename>Root Partition (x86-64)</filename></entry> |
| <entry><filename>/</filename></entry> |
| <entry>On 64-bit x86 systems, the first x86-64 root partition on the disk the EFI ESP is located on is mounted to the root directory <filename>/</filename>.</entry> |
| </row> |
| <row> |
| <entry>69dad710-2ce4-4e3c-b16c-21a1d49abed3</entry> |
| <entry><filename>Root Partition (32-bit ARM)</filename></entry> |
| <entry><filename>/</filename></entry> |
| <entry>On 32-bit ARM systems, the first ARM root partition on the disk the EFI ESP is located on is mounted to the root directory <filename>/</filename>.</entry> |
| </row> |
| <row> |
| <entry>b921b045-1df0-41c3-af44-4c6f280d3fae</entry> |
| <entry><filename>Root Partition (64-bit ARM)</filename></entry> |
| <entry><filename>/</filename></entry> |
| <entry>On 64-bit ARM systems, the first ARM root partition on the disk the EFI ESP is located on is mounted to the root directory <filename>/</filename>.</entry> |
| </row> |
| <row> |
| <entry>993d8d3d-f80e-4225-855a-9daf8ed7ea97</entry> |
| <entry><filename>Root Partition (Itanium/IA-64)</filename></entry> |
| <entry><filename>/</filename></entry> |
| <entry>On Itanium systems, the first Itanium root partition on the disk the EFI ESP is located on is mounted to the root directory <filename>/</filename>.</entry> |
| </row> |
| <row> |
| <entry>933ac7e1-2eb4-4f13-b844-0e14e2aef915</entry> |
| <entry>Home Partition</entry> |
| <entry><filename>/home/</filename></entry> |
| <entry>The first home partition on the disk the root partition is located on is mounted to <filename>/home/</filename>.</entry> |
| </row> |
| <row> |
| <entry>3b8f8425-20e0-4f3b-907f-1a25a76f98e8</entry> |
| <entry>Server Data Partition</entry> |
| <entry><filename>/srv/</filename></entry> |
| <entry>The first server data partition on the disk the root partition is located on is mounted to <filename>/srv/</filename>.</entry> |
| </row> |
| <row> |
| <entry>4d21b016-b534-45c2-a9fb-5c16e091fd2d</entry> |
| <entry>Variable Data Partition</entry> |
| <entry><filename>/var/</filename></entry> |
| <entry>The first variable data partition on the disk the root partition is located on 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>7ec6f557-3bc5-4aca-b293-16ef5df639d1</entry> |
| <entry>Temporary Data Partition</entry> |
| <entry><filename>/var/tmp/</filename></entry> |
| <entry>The first temporary data partition on the disk the root partition is located on is mounted to <filename>/var/tmp/</filename>.</entry> |
| </row> |
| <row> |
| <entry>0657fd6d-a4ab-43c4-84e5-0933c84b4f4f</entry> |
| <entry>Swap</entry> |
| <entry>n/a</entry> |
| <entry>All swap partitions located on the disk the root partition is located on are enabled.</entry> |
| </row> |
| <row> |
| <entry>c12a7328-f81f-11d2-ba4b-00a0c93ec93b</entry> |
| <entry>EFI System Partition (ESP)</entry> |
| <entry><filename>/efi/</filename> or <filename>/boot/</filename></entry> |
| <entry>The first ESP located on the disk the root partition is located on is mounted to <filename>/boot/</filename> or <filename>/efi/</filename>, see below.</entry> |
| </row> |
| <row> |
| <entry>bc13c2ff-59e6-4262-a352-b275fd6f7172</entry> |
| <entry>Extended Boot Loader Partition</entry> |
| <entry><filename>/boot/</filename></entry> |
| <entry>The first Extended Boot Loader 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 Attributes</title> |
| <tgroup cols='4' align='left' colsep='1' rowsep='1'> |
| <colspec colname="attribute" /> |
| <colspec colname="value" /> |
| <colspec colname="where" /> |
| <colspec colname="explanation" /> |
| <thead> |
| <row> |
| <entry>Name</entry> |
| <entry>Value</entry> |
| <entry>Applicable to</entry> |
| <entry>Explanation</entry> |
| </row> |
| </thead> |
| <tbody> |
| <row> |
| <entry><constant>GPT_FLAG_READ_ONLY</constant></entry> |
| <entry>0x1000000000000000</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>GPT_FLAG_NO_AUTO</constant></entry> |
| <entry>0x8000000000000000</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>GPT_FLAG_NO_BLOCK_IO_PROTOCOL</constant></entry> |
| <entry>0x0000000000000002</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>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 negative value may be used to disable it. |
| </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> |