systemctl: make "systemctl is-system-running" return "offline" if we are not booted with systemd

This sounds like the better place to expose this than in "systemd-notify
--booted".

Also document the so far undocumented "unknown" state the command might
return. And rearrange the table of states documented to be more like the
one for "is-running".

Also, don't document the precise exit code of this function, just say
errors are reported != 0 or > 0...

3 files changed, 49 insertions, 14 deletions

diff --git a/man/systemctl.xml b/man/systemctl.xml
index c1359d1678..9e9ba5a5b6 100644
--- a/man/systemctl.xml
+++ b/man/systemctl.xml
@@ -1120,9 +1120,9 @@ kobject-uevent 1 systemd-udevd-kernel.socket systemd-udevd.service
               <tgroup cols='3'>
                 <thead>
                   <row>
-                    <entry>Printed string</entry>
-                    <entry>Meaning</entry>
-                    <entry>Return value</entry>
+                    <entry>Name</entry>
+                    <entry>Description</entry>
+                    <entry>Exit Code</entry>
                   </row>
                 </thead>
                 <tbody>
@@ -1137,7 +1137,7 @@ kobject-uevent 1 systemd-udevd-kernel.socket systemd-udevd.service
                   <row>
                     <entry><literal>linked</literal></entry>
                     <entry morerows='1'>Made available through a symlink to the unit file (permanently or just in <filename>/run</filename>).</entry>
-                    <entry morerows='1'>1</entry>
+                    <entry morerows='1'>&gt; 0</entry>
                   </row>
                   <row>
                     <entry><literal>linked-runtime</literal></entry>
@@ -1145,7 +1145,7 @@ kobject-uevent 1 systemd-udevd-kernel.socket systemd-udevd.service
                   <row>
                     <entry><literal>masked</literal></entry>
                     <entry morerows='1'>Disabled entirely (permanently or just in <filename>/run</filename>).</entry>
-                    <entry morerows='1'>1</entry>
+                    <entry morerows='1'>&gt; 0</entry>
                   </row>
                   <row>
                     <entry><literal>masked-runtime</literal></entry>
@@ -1163,7 +1163,7 @@ kobject-uevent 1 systemd-udevd-kernel.socket systemd-udevd.service
                   <row>
                     <entry><literal>disabled</literal></entry>
                     <entry>Unit file is not enabled.</entry>
-                    <entry>1</entry>
+                    <entry>&gt; 0</entry>
                   </row>
                 </tbody>
               </tgroup>
@@ -1474,22 +1474,25 @@ kobject-uevent 1 systemd-udevd-kernel.socket systemd-udevd.service
 
           <listitem>
             <para>Checks whether the system is operational. This
-            returns success when the system is fully up and running,
-            meaning not in startup, shutdown or maintenance
-            mode. Failure is returned otherwise. In addition, the
+            returns success (exit code 0) when the system is fully up
+            and running, specifically not in startup, shutdown or
+            maintenance mode, and with no failed services. Failure is
+            returned otherwise (exit code non-zero). In addition, the
             current state is printed in a short string to standard
             output, see table below. Use <option>--quiet</option> to
             suppress this output.</para>
 
             <table>
-              <title>Manager Operational States</title>
-              <tgroup cols='2'>
-                <colspec colname='name' />
-                <colspec colname='description' />
+              <title><command>is-system-running</command> output</title>
+              <tgroup cols='3'>
+                <colspec colname='name'/>
+                <colspec colname='description'/>
+                <colspec colname='exit-code'/>
                 <thead>
                   <row>
                     <entry>Name</entry>
                     <entry>Description</entry>
+                    <entry>Exit Code</entry>
                   </row>
                 </thead>
                 <tbody>
@@ -1499,32 +1502,53 @@ kobject-uevent 1 systemd-udevd-kernel.socket systemd-udevd.service
                     <filename>basic.target</filename> is reached
                     or the <varname>maintenance</varname> state entered.
                     </para></entry>
+                    <entry>&gt; 0</entry>
                   </row>
                   <row>
                     <entry><varname>starting</varname></entry>
                     <entry><para>Late bootup, before the job queue
                     becomes idle for the first time, or one of the
                     rescue targets are reached.</para></entry>
+                    <entry>&gt; 0</entry>
                   </row>
                   <row>
                     <entry><varname>running</varname></entry>
                     <entry><para>The system is fully
                     operational.</para></entry>
+                    <entry>0</entry>
                   </row>
                   <row>
                     <entry><varname>degraded</varname></entry>
                     <entry><para>The system is operational but one or more
                     units failed.</para></entry>
+                    <entry>&gt; 0</entry>
                   </row>
                   <row>
                     <entry><varname>maintenance</varname></entry>
                     <entry><para>The rescue or emergency target is
                     active.</para></entry>
+                    <entry>&gt; 0</entry>
                   </row>
                   <row>
                     <entry><varname>stopping</varname></entry>
                     <entry><para>The manager is shutting
                     down.</para></entry>
+                    <entry>&gt; 0</entry>
+                  </row>
+                  <row>
+                    <entry><varname>offline</varname></entry>
+                    <entry><para>The manager is not
+                    running. Specifically, this is the operational
+                    state if an incompatible program is running as
+                    system manager (PID 1).</para></entry>
+                    <entry>&gt; 0</entry>
+                  </row>
+                  <row>
+                    <entry><varname>unknown</varname></entry>
+                    <entry><para>The operational state could not be
+                    determined, due to lack of resources or another
+                    error cause.</para></entry>
+                    <entry>&gt; 0</entry>
                   </row>
                 </tbody>
               </tgroup>
diff --git a/man/systemd-notify.xml b/man/systemd-notify.xml
index 06d5ae5319..5832cc6759 100644
--- a/man/systemd-notify.xml
+++ b/man/systemd-notify.xml
@@ -124,7 +124,12 @@
         systemd, non-zero otherwise. If this option is passed, no
         message is sent. This option is hence unrelated to the other
         options. For details about the semantics of this option, see
-        <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
+        <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>. An
+        alternative way to check for this state is to call
+        <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+        with the <command>is-system-running</command> command. It will
+        return <literal>offline</literal> if the system was not booted
+        with systemd.  </para></listitem>
       </varlistentry>
 
       <xi:include href="standard-options.xml" xpointer="help" />
diff --git a/src/systemctl/systemctl.c b/src/systemctl/systemctl.c
index 56c7982b8f..2b9de5d016 100644
--- a/src/systemctl/systemctl.c
+++ b/src/systemctl/systemctl.c
@@ -5753,6 +5753,12 @@ static int is_system_running(sd_bus *bus, char **args) {
         _cleanup_free_ char *state = NULL;
         int r;
 
+        if (arg_transport == BUS_TRANSPORT_LOCAL && !sd_booted()) {
+                if (!arg_quiet)
+                        puts("offline");
+                return EXIT_FAILURE;
+        }
+
         r = sd_bus_get_property_string(
                         bus,
                         "org.freedesktop.systemd1",