Virtualization - Old Hat?

This is a collection of tips and tricks I picked up while learning and working with Docker and Docker Compose on my home server and web server. Container Configuration Environment Variables Where to Define Environment Variables Environment variables are a common way to configure containers. To keep things organized, don’t put them in your Compose file but into dedicated files with the extension env. env_file vs. .env .env file: this “special” file can be used to set environment variable for use in the Compose file. The variables specified in .env are not available in the container. env_file: this section in the Docker Compose file lets you specify files that contain environment variables for use in the container. The variables specified in this section are not available in the Compose file. Bind Mounts vs. Docker Volumes Bind mounts let you control the directory structure. This has the advantage that you know exactly what gets stored where in the host’s file system. It has the disadvantage that you need to create the directory structure before you can start a container. Docker volumes are managed by the Docker engine. They’re stored in /var/lib/docker, “far away” from the Compose file. Personally, I very much prefer bind mounts because of the control they offer. I use subdirectories relative to the Compose file, e.g., ./data:/data. Keeping the container configuration and the container data in one place facilitates backups. Networking Expose vs. Ports Expose serves as documentation which ports a container is accessible on. Note: container ports are always accessible from other containers on the same Docker network. Ports makes container ports accessible to the host. Most of my services are accessible through the Caddy reverse proxy only. Opening ports to the host is, therefore, only rarely necessary. Static IP Address on the Host Network Use the Macvlan Docker network to attach a container directly to the host’s local network. Assign a static IP address by specifying the ip_range parameter in the ipam section of the Docker Compose file. See this configuration for an example. Disable Macvlan Container/Host Isolation Containers on a Macvlan network are isolated from the host. While the container can contact other machines on the local network, communications with the host are blocked. To work around that, create a virtual link with a route that points to the container’s IP address (example). Time Zone Containers should know about your local time zone. To achieve that, make it a habit to pass in /etc/localtime as a read-only volume to every container: