man: import org.freedesktop.machine1(3) from the wiki

The wiki was primarily describing the D-Bus API, but it also had a large
introduction to the daemon functionality. I moved that latter part into
the page that describes the daemon, and the API description into the new
page.

This is mostly a straighforward import. Apart from some required formatting
changes, I removed obvious repetitions, and made tiny grammar and typo fixes
where I noticed them. The goal is not to have a perfect text immediately.

<interfacename>org.foo.bar</interface> is used for interface names,
<function>function()</function> for methods, and <function>signal</function>
(no parentheses) for signal names. In D-Bus, signals are similar to methods,
and docbook doesn't have a nice tag for them.

1 files changed, 79 insertions, 12 deletions

diff --git a/man/systemd-machined.service.xml b/man/systemd-machined.service.xml
index 8771434e5a..b5fad154e7 100644
--- a/man/systemd-machined.service.xml
+++ b/man/systemd-machined.service.xml
@@ -29,24 +29,91 @@
   <refsect1>
     <title>Description</title>
 
-    <para><command>systemd-machined</command> is a system service that
-    keeps track of virtual machines and containers, and processes
-    belonging to them.</para>
+    <para><command>systemd-machined</command> is a system service that keeps track of locally running virtual
+    machines and containers.</para>
+
+    <para><command>systemd-machined</command> is useful for registering and keeping track of both OS
+    containers (containers that share the host kernel but run a full init system of their own and behave in
+    most regards like a full virtual operating system rather than just one virtualized app) and full virtual
+    machines (virtualized hardware running normal operating systems and possibly different kernels).</para>
+
+    <para><command>systemd-machined</command> should <emphasis>not</emphasis> be used for registering/keeping
+    track of application sandbox containers. A <emphasis>machine</emphasis> in the context of
+    <command>systemd-machined</command> is supposed to be an abstract term covering both OS containers and
+    full virtual machines, but not application sandboxes.</para>
+
+    <para>Machines registered with machined are exposed in various ways in the system. For example:
+    <itemizedlist>
+      <listitem><para>Tools like
+      <citerefentry project='man-pages'><refentrytitle>ps</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+      will show to which machine a specific process belongs in a column of
+      its own, and so will
+      <ulink url="https://help.gnome.org/users/gnome-system-monitor/">gnome-system-monitor</ulink> or
+      <citerefentry><refentrytitle>systemd-cgls</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
+      </listitem>
+
+      <listitem><para>systemd's various tools
+      (<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>loginctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>hostnamectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>timedatectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>localectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, ...)
+      support the <option>-M</option> switch to operate on local containers instead of the host system.
+      </para></listitem>
+
+      <listitem><para><command>systemctl list-machines</command> will show the system state of all local
+      containers, connecting to the container's init system for that.</para></listitem>
+
+      <listitem><para>systemctl's <option>--recursive</option> switch has the effect of not only showing the
+      locally running services, but recursively the services of all registered containers.</para></listitem>
+
+      <listitem><para>The <command>machinectl</command> command provides access to a number of useful
+      operations on registered containers, such as introspecting them, rebooting, shutting them down, and
+      getting a login prompt on them.</para></listitem>
+
+      <listitem><para>The
+      <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry> library
+      exposes the
+      <citerefentry><refentrytitle>sd_bus_open_system_container</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+      call to connect to the system bus of any registered container.</para></listitem>
+
+      <listitem><para>The
+      <citerefentry><refentrytitle>nss-mymachines</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+      module makes sure all registered containers can be resolved via normal glibc
+      <citerefentry project='man-pages'><refentrytitle>gethostbyname</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+      or
+      <citerefentry project='man-pages'><refentrytitle>getaddrinfo</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+      calls.</para></listitem>
+    </itemizedlist></para>
 
     <para>See
     <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>
     for some examples on how to run containers with OS tools.</para>
 
-    <para>Use
-    <citerefentry><refentrytitle>nss-mymachines</refentrytitle><manvolnum>8</manvolnum></citerefentry>
-    to make the names of local containers known to
-    <command>systemd-machined</command> locally resolvable as host
-    names.</para>
+    <para>If you are interested in writing a VM or container manager that makes use of machined, please have
+    look at <ulink url="https://www.freedesktop.org/wiki/Software/systemd/writing-vm-managers">Writing
+    Virtual Machine or Container Managers</ulink>. Also see the <ulink
+    url="https://www.freedesktop.org/wiki/Software/systemd/ControlGroupInterface/">New Control Group
+    Interfaces</ulink>.</para>
 
-    <para>See the
-    <ulink url="https://www.freedesktop.org/wiki/Software/systemd/machined">
-    machined D-Bus API Documentation</ulink> for information about the
-    APIs <filename>systemd-machined</filename> provides.</para>
+    <para>The daemon provides both a C library interface
+    (which is shared with <citerefentry><refentrytitle>systemd-logind.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>)
+    as well as a D-Bus interface.
+    The library interface may be used to introspect and watch the state of virtual machines/containers.
+    The bus interface provides the same but in addition may also be used to register or terminate
+    machines.
+    For more information please consult
+    <citerefentry><refentrytitle>sd-login</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+    and
+    <citerefentry><refentrytitle>org.freedesktop.machine1</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
+    </para>
+
+    <para>A small companion daemon
+    <citerefentry><refentrytitle>systemd-importd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+    is also available, which implements importing, exporting, and downloading of container and VM images.
+    </para>
   </refsect1>
 
   <refsect1>