Integrating a revert guide

Signed-off-by: Anatoli Nicolae <[email protected]>

notes/install-podman.md

@@ -10,16 +10,22 @@ queries:
   - how to install docker
 ---
 
-<Warning>
+<Error>
 
 Podman interferes with typical ApisCP behaviour, changing firewall rules to accomodate container routing definitions.
 
 A side-effect of this behaviour manifests with containers becoming unresponsive when accessing exposed ports form the host or outside world, as firewall rules are refreshed on the panel's side efectively removing Podman-added rules.
 
+</Error>
+
+<Warning>
+
 Docker is a preferred alternative in this case.
 
 </Warning>
 
+## Installing Podman
+
 Podman is the supported drop-in replacement for RHEL 8+.
 
 To install Podman, run the following commands:
@@ -36,3 +42,51 @@ In order for containers to keep running, you need to [tell systemd to linger you
 loginctl show-user <user> --property Linger
 loginctl enable-linger <user>
 ```
+
+## Switching from Podman back to Docker
+
+Switching back is quite an easy process:
+
+```bash
+# Remove podman or other docker-related packages
+dnf remove docker docker-client docker-client-latest docker-common docker-latest docker-latest-logrotate docker-logrotate docker-engine podman runc
+
+# Add Docker CE repo
+dnf config-manager --add-repo https://download.docker.com/linux/rhel/docker-ce.repo
+
+# Install docker-ce package
+dnf install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin
+
+# Stop unit for reconfiguration
+systemctl stop docker
+
+# Fix ExecStart definition with a unit override
+mkdir -p /etc/systemd/system/docker.service.d
+cat << EOF > /etc/systemd/system/docker.service.d/override.conf
+[Service]
+# This clears any ExecStart= inherited from docker.service
+ExecStart=
+ExecStart=/usr/bin/dockerd --containerd=/run/containerd/containerd.sock
+EOF
+
+# Reload systemd daemon
+systemctl daemon-reload
+
+# Docker group should be created by default, but just in case
+groupadd --system docker
+
+# Allow docker to be accessible under /.socket
+echo -e '{\n\t"hosts": ["unix:///var/run/docker.sock", "unix:///.socket/docker.sock"],\n\t"group": "docker"\n}' > /etc/docker/daemon.json
+
+# Enable and start the unit
+systemctl enable --now docker
+
+# Check if this returns an empty list of containers. If it returns an error, investigate.
+docker ps
+```
+
+<Check>
+
+If you have systemd-backed container definitions you will need to recreate containers in Docker via `docker run` or `docker-compose`.
+
+</Check>