Podman: Advanced Concepts

Pods in Podman#

Understanding Pods#

• What is a Pod? A way to run multiple containers together with shared resources and networking.
• Podman Pods vs. Kubernetes Pods – Podman pods mimic Kubernetes behavior but don’t require a full cluster.
• Use Cases – Useful for running multi-container applications (e.g., a web server and database).

Creating and Managing Pods#

• Create a Pod:

  podman pod create --name mypod -p 8080:80

• Add a container to the Pod:

  podman run -dt --pod mypod nginx

• View Pod details:

  podman pod ps
  podman pod inspect mypod

• Stop and remove a Pod:

  podman pod stop mypod
  podman pod rm mypod

Managing Container Networks#

Container Networking Basics#

• Network Modes:
  • Bridge (default): Containers get unique IPs and can communicate.
  • Host: Uses the host’s network, offering better performance but less isolation.
  • None: No networking.

Creating Custom Networks#

• List existing networks:

  podman network ls

• Create a custom network:

  podman network create mynetwork

• Run a container in a custom network:

  podman run -dt --network mynetwork nginx

• Inspect network details:

  podman network inspect mynetwork

Connecting Containers#

• Expose a container on a specific port:

  podman run -dt -p 8080:80 nginx

• Connect two containers to the same network:

  podman network connect mynetwork container1
  podman network connect mynetwork container2

Volumes and Persistent Storage#

Understanding Storage in Podman#

• Bind Mounts vs. Volumes:
  • Bind Mounts: Directly link to host paths.
  • Volumes: Managed by Podman, offering better portability.
• When to Use Persistent Storage? When data needs to outlive the container.

Managing Volumes#

• Create a volume:

  podman volume create myvolume

• Mount a volume in a container:

  podman run -dt -v myvolume:/data nginx

• List and inspect volumes:

  podman volume ls
  podman volume inspect myvolume

• Remove a volume:

  podman volume rm myvolume

Using Bind Mounts#

• Mount a host directory in a container:

  podman run -dt -v /host/data:/container/data nginx

Container Health Checks and Management#

Understanding Health Checks#

• Why? Ensures containers stay functional and responsive.
• How? Define a health check command that regularly verifies container status.

Implementing Health Checks#

• Run a container with a health check:

  podman run -d --name mywebserver \
    --health-cmd "curl -f http://localhost || exit 1" \
    --health-interval 30s nginx

• Check container health status:

  podman inspect --format='{{.State.Healthcheck}}' mywebserver

Managing Container Resources#

• Limit CPU and memory usage:

  podman run -dt --memory=512m --cpus=1 nginx

• Monitor container performance:

  podman stats

Hands-on Exercises#

1. Create and Manage a Pod with Multiple Containers#

podman pod create --name myapp -p 8080:80
podman run -dt --pod myapp nginx
podman run -dt --pod myapp redis
podman pod ps

2. Set Up a Custom Network and Connect Containers#

podman network create mynetwork
podman run -dt --network mynetwork --name webserver nginx
podman run -dt --network mynetwork --name database redis
podman network inspect mynetwork

3. Implement Health Checks for a Web Server#

podman run -d --name healthcheck-nginx \
  --health-cmd "curl -f http://localhost || exit 1" \
  --health-interval 30s \
  nginx
podman inspect --format='{{.State.Healthcheck}}' healthcheck-nginx

Summary & Next Steps#

Key Takeaways#

• Pods allow multiple containers to share resources and networking.
• Custom networks improve container communication and security.
• Persistent storage ensures data survives beyond container lifetimes.
• Health checks keep applications running smoothly.

Next Module: Building and Managing Images#

Up next: We’ll cover building container images, managing registries, and securing your images.