Docs: Add containerd setup instructions for Ubuntu 18.04/20.04

Author: karras

content/en/docs/setup/production-environment/container-runtimes.md

@@ -124,6 +124,24 @@ sudo mkdir -p /etc/containerd
 sudo containerd config default > /etc/containerd/config.toml
 ```
 
+```shell
+# Restart containerd
+sudo systemctl restart containerd
+```
+{{% /tab %}}
+{{% tab name="Ubuntu 18.04/20.04" %}}
+
+```shell
+# (Install containerd)
+sudo apt-get update && sudo apt-get install -y containerd
+```
+
+```shell
+# Configure containerd
+sudo mkdir -p /etc/containerd
+sudo containerd config default > /etc/containerd/config.toml
+```
+
 ```shell
 # Restart containerd
 sudo systemctl restart containerd