Merge pull request #2903 from ccin2p3/documentation/libvirt

add some useful info to libvirt manpage

diff --combined src/collectd.conf.pod
index 6e6d6ea,5590c5b..b1f8eb4
--- 1/src/collectd.conf.pod
--- 2/src/collectd.conf.pod
+++ b/src/collectd.conf.pod
@@@ -7359,7 -7359,6 +7359,7 @@@ parameters and set of user-defined quer
      <Node "example">
          Host "localhost"
          Port "6379"
 +        #Socket "/var/run/redis/redis.sock"
          Timeout 2000
          ReportCommandStats false
          ReportCpuUsage true
@@@ -7393,11 -7392,6 +7393,11 @@@ The B<Port> option is the TCP port on w
  connections. Either a service name of a port number may be given. Please note
  that numerical port numbers must be given as a string, too.
  
 +=item B<Socket> I<Path>
 +
 +Connect to Redis using the UNIX domain socket at I<Path>. If this
 +setting is given, the B<Hostname> and B<Port> settings are ignored.
 +
  =item B<Password> I<Password>
  
  Use I<Password> to authenticate when connecting to I<Redis>.
@@@ -9106,6 -9100,40 +9106,40 @@@ only on the host system
  
  Only I<Connection> is required.
  
+ Consider the following example config:
+ 
+  <Plugin "virt">
+    Connection "qemu:///system"
+    HostnameFormat "hostname"
+    InterfaceFormat "address"
+    PluginInstanceFormat "name"
+  </Plugin>
+ 
+ It will generate the following values:
+ 
+   node42.example.com/virt-instance-0006f26c/disk_octets-vda
+   node42.example.com/virt-instance-0006f26c/disk_ops-vda
+   node42.example.com/virt-instance-0006f26c/if_dropped-ca:fe:ca:fe:ca:fe
+   node42.example.com/virt-instance-0006f26c/if_errors-ca:fe:ca:fe:ca:fe
+   node42.example.com/virt-instance-0006f26c/if_octets-ca:fe:ca:fe:ca:fe
+   node42.example.com/virt-instance-0006f26c/if_packets-ca:fe:ca:fe:ca:fe
+   node42.example.com/virt-instance-0006f26c/memory-actual_balloon
+   node42.example.com/virt-instance-0006f26c/memory-available
+   node42.example.com/virt-instance-0006f26c/memory-last_update
+   node42.example.com/virt-instance-0006f26c/memory-major_fault
+   node42.example.com/virt-instance-0006f26c/memory-minor_fault
+   node42.example.com/virt-instance-0006f26c/memory-rss
+   node42.example.com/virt-instance-0006f26c/memory-swap_in
+   node42.example.com/virt-instance-0006f26c/memory-swap_out
+   node42.example.com/virt-instance-0006f26c/memory-total
+   node42.example.com/virt-instance-0006f26c/memory-unused
+   node42.example.com/virt-instance-0006f26c/memory-usable
+   node42.example.com/virt-instance-0006f26c/virt_cpu_total
+   node42.example.com/virt-instance-0006f26c/virt_vcpu-0
+ 
+ You can get information on the metric's units from the online libvirt documentation.
+ For instance, I<virt_cpu_total> is in nanoseconds.
+ 
  =over 4
  
  =item B<Connection> I<uri>
@@@ -9208,7 -9236,8 +9242,8 @@@ B<uuid> means use the guest's UUID. Thi
  same guest across migrations.
  
  B<hostname> means to use the global B<Hostname> setting, which is probably not
- useful on its own because all guests will appear to have the same name.
+ useful on its own because all guests will appear to have the same name. This is
+ useful in conjunction with B<PluginInstanceFormat> though.
  
  You can also specify combinations of these fields. For example B<name uuid>
  means to concatenate the guest name and UUID (with a literal colon character