mirror of
https://github.com/systemd/systemd.git
synced 2026-08-09 17:38:42 +00:00
104970a8bd
Adds dm-clone device setup at boot via a new /etc/clonetab config file, following the crypttab/veritytab pattern. - Add systemd-clonesetup-generator to parse /etc/clonetab and generate units. - Add systemd-clonesetup binary to create/remove dm-clone devices via ioctl. - Add clonesetup.target for ordering dm-clone activation at boot. - Add region_size= option in clonetab to configure dm-clone hydration granularity. - Add clonetab(5) and systemd-clonesetup-generator(8) man pages. Fixes: https://github.com/systemd/systemd/issues/39500
122 lines
5.3 KiB
XML
122 lines
5.3 KiB
XML
<?xml version="1.0"?>
|
|
<!--*-nxml-*-->
|
|
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
|
|
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
|
|
<!--
|
|
SPDX-License-Identifier: LGPL-2.1-or-later
|
|
-->
|
|
<refentry id="clonetab" xmlns:xi="http://www.w3.org/2001/XInclude">
|
|
|
|
<refentryinfo>
|
|
<title>clonetab</title>
|
|
<productname>systemd</productname>
|
|
</refentryinfo>
|
|
|
|
<refmeta>
|
|
<refentrytitle>clonetab</refentrytitle>
|
|
<manvolnum>5</manvolnum>
|
|
</refmeta>
|
|
|
|
<refnamediv>
|
|
<refname>clonetab</refname>
|
|
<refpurpose>Configuration for dm-clone block devices</refpurpose>
|
|
</refnamediv>
|
|
|
|
<refsynopsisdiv>
|
|
<para><filename>/etc/clonetab</filename></para>
|
|
</refsynopsisdiv>
|
|
|
|
<refsect1>
|
|
<title>Description</title>
|
|
|
|
<para>The <filename>/etc/clonetab</filename> file describes
|
|
dm-clone block devices that are set up during system boot.</para>
|
|
|
|
<para>Empty lines and lines starting with the <literal>#</literal>
|
|
character are ignored. Each of the remaining lines describes one
|
|
dm-clone device. Fields are delimited by white space.</para>
|
|
|
|
<para>Each line is in the form<programlisting><replaceable>name</replaceable> <replaceable>source-device</replaceable> <replaceable>destination-device</replaceable> <replaceable>metadata-device</replaceable> [<replaceable>options</replaceable>]</programlisting>
|
|
The first four fields are mandatory, the fifth is optional.</para>
|
|
|
|
<para>The five fields of <filename>/etc/clonetab</filename> are defined as follows:</para>
|
|
|
|
<orderedlist>
|
|
|
|
<listitem><para>The first field contains the name of the resulting dm-clone device; its
|
|
block device is set up below <filename>/dev/mapper/</filename>.</para></listitem>
|
|
|
|
<listitem><para>The second field contains a path to the read-only source block device.
|
|
This is the device whose data is cloned to the destination device. Reads to regions not
|
|
yet hydrated are served directly from this device.</para></listitem>
|
|
|
|
<listitem><para>The third field contains a path to the writable destination block device.
|
|
The source device's data is copied here in the background. It must be at least as
|
|
large as the source device.</para></listitem>
|
|
|
|
<listitem><para>The fourth field contains a path to the metadata block device. This
|
|
small device tracks which regions of the destination have been hydrated and is managed
|
|
exclusively by dm-clone.</para></listitem>
|
|
|
|
<listitem><para>The fifth field, if present, contains comma-separated <literal>key=value</literal>
|
|
options. The following option is supported:</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><option>region-size=<replaceable>BYTES</replaceable></option></term>
|
|
<listitem><para>Controls the granularity of background hydration copying — how much
|
|
data is copied at a time. Region size is specified in bytes (standard suffixes like
|
|
<literal>K</literal>, <literal>M</literal>, <literal>G</literal> are supported), and must
|
|
correspond to a power of two between 4 KiB and 1 GiB. For example,
|
|
<literal>region-size=4K</literal> or <literal>region-size=4096</literal> sets a 4 KiB region size.</para>
|
|
|
|
<para>
|
|
One region is the atomic unit dm-clone tracks: it is either fully hydrated (copied to the destination)
|
|
or not, never partially. If a copy is interrupted mid-region, that whole region is
|
|
retried from scratch on next boot. Smaller regions mean finer progress tracking;
|
|
larger regions reduce metadata overhead. Defaults to <literal>4K</literal>. For background, see
|
|
<ulink url="https://www.kernel.org/doc/html/latest/admin-guide/device-mapper/dm-clone.html">dm-clone kernel documentation</ulink>.
|
|
</para>
|
|
|
|
<xi:include href="version-info.xml" xpointer="v262"/></listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
<para>If no options are needed, the field may be omitted entirely or
|
|
<literal>-</literal> may be used as a placeholder.</para>
|
|
</listitem>
|
|
|
|
</orderedlist>
|
|
|
|
<para>At early boot and when the system manager configuration is reloaded, this file is
|
|
translated into native systemd units by
|
|
<citerefentry><refentrytitle>systemd-clonesetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Examples</title>
|
|
|
|
<example>
|
|
<title>Simple clone without options</title>
|
|
<para>Clone a source device to a destination, using a separate metadata device:</para>
|
|
<programlisting>mydevice /dev/sdb /dev/sdc /dev/sdd</programlisting>
|
|
</example>
|
|
|
|
<example>
|
|
<title>Clone with custom region size</title>
|
|
<para>Clone a source device to a destination with a custom region size of 8 KiB:</para>
|
|
<programlisting>mydevice /dev/sdb /dev/sdc /dev/sdd region-size=8K</programlisting>
|
|
</example>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>See Also</title>
|
|
<para><simplelist type="inline">
|
|
<member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
|
|
<member><citerefentry><refentrytitle>systemd-clonesetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
|
|
<member><citerefentry project='die-net'><refentrytitle>dmsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
|
|
</simplelist></para>
|
|
</refsect1>
|
|
|
|
</refentry>
|