alternatives: New page with alternatives workaround

Workaround for [1] while we wait for [2] to get fixed.

[1] coreos/fedora-coreos-tracker#676
[2] fedora-sysv/chkconfig#9

modules/ROOT/nav.adoc

@@ -28,6 +28,7 @@
 *** xref:customize-nic.adoc[How to Customize a NIC Name]
 *** xref:sysconfig-configure-swaponzram.adoc[Configuring SwapOnZRAM]
 *** xref:kernel-args.adoc[Modifying Kernel Arguments]
+*** xref:alternatives.adoc[Setting alternatives]
 ** OS updates
 *** xref:update-streams.adoc[Update Streams]
 *** xref:auto-updates.adoc[Auto-Updates]

modules/ROOT/pages/alternatives.adoc

@@ -0,0 +1,37 @@
+= Setting alternatives
+
+Due to an https://github.com/fedora-sysv/chkconfig/issues/9[ongoing issue] in how alternatives configurations are stored on the system, Fedora CoreOS systems can not use the usual `alternatives` commands to configure them.
+
+Instead, until this issue is resolved, you can set the symlinks directly in `/etc/alternatives`. For example, to use the nftables based variants of `iptables` commands:
+
+[source,yaml]
+----
+variant: fcos
+version: 1.2.0
+storage:
+  links:
+    - path: /etc/alternatives/iptables
+      target: /usr/sbin/iptables-nft
+      overwrite: true
+      hard: false
+    - path: /etc/alternatives/iptables-restore
+      target: /usr/sbin/iptables-nft-restore
+      overwrite: true
+      hard: false
+    - path: /etc/alternatives/iptables-save
+      target: /usr/sbin/iptables-nft-save
+      overwrite: true
+      hard: false
+    - path: /etc/alternatives/ip6tables
+      target: /usr/sbin/ip6tables-nft
+      overwrite: true
+      hard: false
+    - path: /etc/alternatives/ip6tables-restore
+      target: /usr/sbin/ip6tables-nft-restore
+      overwrite: true
+      hard: false
+    - path: /etc/alternatives/ip6tables-save
+      target: /usr/sbin/ip6tables-nft-save
+      overwrite: true
+      hard: false
+----