Add Docker CE installation instructions page

modules/ROOT/nav.adoc

@@ -35,6 +35,7 @@
 ** xref:proxy.adoc[Proxied Internet Access]
 ** xref:sysconfig-setting-keymap.adoc[Setting Keyboard Layout]
 ** xref:os-extensions.adoc[Adding OS extensions]
+** xref:docker-ce.adoc[Installing Docker CE]
 ** xref:customize-nic.adoc[How to Customize a NIC Name]
 ** xref:sysconfig-configure-swaponzram.adoc[Configuring SwapOnZRAM]
 ** xref:sysconfig-configure-wireguard.adoc[Configuring WireGuard]

modules/ROOT/pages/docker-ce.adoc

@@ -0,0 +1,60 @@
+= Installing Docker CE
+
+By default, Fedora CoreOS comes with out-of-the-box support for `docker` CLI (as provided via https://mobyproject.org/[Moby]).
+However, in some cases Docker Community Edition (CE) may be preferred for various reasons.
+This page explains how to replace the provided version with the latest from the upstream Docker sources.
+
+The recommended approach from the official https://docs.docker.com/engine/install/fedora/[Docker documentation] is to add the Docker repository to your system.
+You can then install and update Docker CE from this repository.
+
+
+== Installing Docker CE on first boot
+
+On provisioning, you can install Docker CE during the first boot of the system via ignition configuration.
+
+.Example Butane config for setting up Docker CE
+[source,yaml,subs="attributes"]
+----
+variant: fcos
+version: {butane-latest-stable-spec}
+systemd:
+  units:
+    # Install Docker CE
+    - name: rpm-ostree-install-docker-ce.service
+      enabled: true
+      contents: |
+        [Unit]
+        Description=Install Docker CE
+        Wants=network-online.target
+        After=network-online.target
+        Before=zincati.service
+        ConditionPathExists=!/var/lib/%N.stamp
+
+        [Service]
+        Type=oneshot
+        RemainAfterExit=yes
+        ExecStart=/usr/bin/curl --output-dir "/etc/yum.repos.d" --remote-name https://download.docker.com/linux/fedora/docker-ce.repo
+        ExecStart=/usr/bin/rpm-ostree override remove moby-engine containerd runc --install docker-ce
+        ExecStart=/usr/bin/touch /var/lib/%N.stamp
+        ExecStart=/usr/bin/systemctl --no-block reboot
+
+        [Install]
+        WantedBy=multi-user.target
+----
+
+
+== Installing Docker CE on a running system
+
+First, download and setup the Docker repository.
+Then you need to remove `moby-engine` and several other conflicting packages that ship by default in the Fedora CoreOS image, install the necessary Docker CE packages, and reboot the system.
+
+[source, bash]
+----
+curl --remote-name https://download.docker.com/linux/fedora/docker-ce.repo
+sudo install --owner 0 --group 0 --mode 644 docker-ce.repo /etc/yum.repos.d/docker-ce.repo
+sudo rpm-ostree override remove moby-engine containerd runc --install docker-ce --reboot
+----
+
+=== Upgrading Docker CE
+
+Docker CE should be upgraded automatically with each new release of Fedora CoreOS.