Add documentation for static IP address on FCOS (#30)

* Add documentation for static IP address on FCOS

* Make changes based on input from @miabbott

* Fix copy/paste error

modules/ROOT/nav.adoc

@@ -8,6 +8,7 @@
 *** xref:producing-ign.adoc[Producing an Ignition File]
 *** xref:fcct-config.adoc[FCCT Specification]
 *** xref:using-fcct.adoc[Using FCCT]
+*** xref:static-ip-config.adoc[Configuring a Static IP Address]
 *** xref:sysctl.adoc[Kernel Tuning]
 *** xref:running-containers.adoc[Running Containers]
 ** OS updates

modules/ROOT/pages/static-ip-config.adoc

@@ -0,0 +1,46 @@
+:experimental:
+= Configuring FCOS to Use a Static IP Address
+By default, an FCOS instance will attempt to grab a DHCP address from the local network. However, if you need FCOS to use a static IP address, you can do so by specifying the NetworkManager configuration in the Ignition configuration file.
+
+As with any custom configuration on FCOS, you can write specific files in the xref:ign-storage.adoc[`storage` node] of the Ignition file.
+
+The following snippet shows how to assign the following to eth0:
+
+* static IP: `192.0.2.10/24`
+* gateway: `192.0.2.1`
+* DNS: `192.168.124.1;1.1.1.1;8.8.8.8`
+* DNS search domain: `redhat.com`
+
+.Example assignment of static IP address
+[source, yaml]
+----
+variant: fcos
+version: 1.0.0
+storage:
+  files:
+    - path: /etc/NetworkManager/system-connections/eth0.nmconnection
+      mode: 0600
+      overwrite: true
+      contents:
+        inline:
+          [connection]
+          type=ethernet
+          interface-name=eth0
+
+          [ethernet]
+          mac-address=<insert MAC address>
+
+          [ipv4]
+          method=manual
+          addresses=192.0.2.10/24
+          gateway=192.0.2.1
+          dns=192.168.124.1;1.1.1.1;8.8.8.8
+          dns-search=redhat.com
+----
+NOTE: During the initramfs portion of the boot process, dracut will attempt to grab a DHCP address. When it times out, Ignition will take over and write the above configuration into the filesystem.
+
+If the interface does not come up correctly on first boot, issue the following commands to force the static IP to take effect:
+
+`nmcli connection down eth0`
+
+`nmcli connection up eth0`