machine-id-commit: merge machine-id-commit functionality into machine-id-setup

And remove machine-id-commit as separate binary.

There's really no point in keeping this separate, as the sources are
pretty much identical, and have pretty identical interfaces. Let's unify
this in one binary.

Given that machine-id-commit was a private binary of systemd (shipped in
/usr/lib/) removing the tool is not an API break.

While we are at it, improve the documentation of the command substantially.

1 files changed, 74 insertions, 26 deletions

diff --git a/man/systemd-machine-id-setup.xml b/man/systemd-machine-id-setup.xml
index 182717f524..efcf408332 100644
--- a/man/systemd-machine-id-setup.xml
+++ b/man/systemd-machine-id-setup.xml
@@ -1,4 +1,4 @@
-<?xml version='1.0'?> <!--*-nxml-*-->
+<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
 
@@ -35,6 +35,12 @@
         <surname>Poettering</surname>
         <email>lennart@poettering.net</email>
       </author>
+      <author>
+        <contrib>Developer</contrib>
+        <firstname>Didier</firstname>
+        <surname>Roche</surname>
+        <email>didrocks@ubuntu.com</email>
+      </author>
     </authorgroup>
   </refentryinfo>
 
@@ -59,30 +65,43 @@
 
     <para><command>systemd-machine-id-setup</command> may be used by
     system installer tools to initialize the machine ID stored in
-    <filename>/etc/machine-id</filename> at install time with a
-    randomly generated ID. See
+    <filename>/etc/machine-id</filename> at install time, with a
+    provisioned or randomly generated ID. See
     <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>
     for more information about this file.</para>
 
-    <para>This tool will execute no operation if
-    <filename>/etc/machine-id</filename> is already
-    initialized.</para>
-
-    <para>If a valid D-Bus machine ID is already configured for the
-    system, the D-Bus machine ID is copied and used to initialize the
-    machine ID in <filename>/etc/machine-id</filename>.</para>
-
-    <para>If run inside a KVM virtual machine and a UUID is passed via
-    the <option>-uuid</option> option, this UUID is used to initialize
-    the machine ID instead of a randomly generated one. The caller
-    must ensure that the UUID passed is sufficiently unique and is
-    different for every booted instanced of the VM.</para>
-
-    <para>Similar, if run inside a Linux container environment and a
-    UUID is set for the container this is used to initialize the
-    machine ID. For details see the documentation of the <ulink
-    url="http://www.freedesktop.org/wiki/Software/systemd/ContainerInterface">Container
-    Interface</ulink>.</para>
+    <para>If the tool is invoked without the <option>--commit</option>
+    switch <filename>/etc/machine-id</filename> is initialized with a
+    valid, new machined ID if it is missing or empty. The new machine
+    ID will be acquired in the following fashion:</para>
+
+    <orderedlist>
+      <listitem><para>If a valid D-Bus machine ID is already
+      configured for the system, the D-Bus machine ID is copied and
+      used to initialize the machine ID in
+      <filename>/etc/machine-id</filename>.</para></listitem>
+
+      <listitem><para>If run inside a KVM virtual machine and a UUID
+      is was configured (via the <option>-uuid</option>
+      option), this UUID is used to initialize the machine ID. The
+      caller must ensure that the UUID passed is sufficiently unique
+      and is different for every booted instance of the
+      VM.</para></listitem>
+
+      <listitem><para>Similar, if run inside a Linux container
+      environment and a UUID is configured for the container this is
+      used to initialize the machine ID. For details see the
+      documentation of the <ulink
+      url="http://www.freedesktop.org/wiki/Software/systemd/ContainerInterface">Container
+      Interface</ulink>.</para></listitem>
+
+      <listitem><para>Otherwise a new ID is randomly
+      generated.</para></listitem>
+    </orderedlist>
+
+    <para>The <option>--commit</option> switch may be used to commit a
+    transient machined ID to disk, making it persistent. For details,
+    see below.</para>
 
     <para>Use
     <citerefentry><refentrytitle>systemd-firstboot</refentrytitle><manvolnum>1</manvolnum></citerefentry>
@@ -97,13 +116,41 @@
     <para>The following options are understood:</para>
 
     <variablelist>
+
       <varlistentry>
         <term><option>--root=<replaceable>root</replaceable></option></term>
-        <listitem><para>Takes a directory path as an argument. All
-        paths will be prefixed with the given alternate
-        <replaceable>root</replaceable> path, including config search
-        paths. </para></listitem>
+        <listitem><para>Takes a directory path as argument. All paths
+        operated will be prefixed with the given alternate
+        <replaceable>root</replaceable> path, including the path for
+        <filename>/etc/machine-id</filename> itself.</para></listitem>
       </varlistentry>
+
+      <varlistentry>
+        <term><option>--commit</option></term>
+        <listitem><para>Commit a transient machine ID to disk. This
+        command may be used to convert a transient machine ID into a
+        persistent one. A transient machine ID file is one that was
+        bind mounted from a memory file system (usually
+        <literal>tmpfs</literal>) to
+        <filename>/etc/machine-id</filename> during the early phase of
+        the boot process. This may happen because
+        <filename>/etc</filename> is initially read-only and was
+        missing a valid machine ID file at that point.</para>
+
+        <para>This command will execute no operation if
+        <filename>/etc/machine-id</filename> is not mounted from a
+        memory file system, or if <filename>/etc</filename> is
+        read-only. The command will write the current transient
+        machine ID to disk and unmount the
+        <filename>/etc/machine-id</filename> mount point in a
+        race-free manner to ensure that this file is always valid and
+        accessible for other processes.</para>
+
+        <para>This command is primarily used by the
+        <citerefentry><refentrytitle>systemd-machine-id-commit.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+        early-boot service.</para></listitem>
+      </varlistentry>
+
       <xi:include href="standard-options.xml" xpointer="help" />
       <xi:include href="standard-options.xml" xpointer="version" />
     </variablelist>
@@ -122,6 +169,7 @@
     <para>
       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>systemd-machine-id-commit.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
       <citerefentry project='dbus'><refentrytitle>dbus-uuidgen</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>systemd-firstboot</refentrytitle><manvolnum>1</manvolnum></citerefentry>
     </para>