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devops/containers/podman/SKILL.md

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+---
+name: podman
+description: Manage containers using Podman, the daemonless container engine. Run rootless containers, create pods, manage images, and use Docker-compatible commands. Use when working with Podman or requiring rootless container operations.
+license: MIT
+metadata:
+  author: devops-skills
+  version: "1.0"
+---
+
+# Podman
+
+Run and manage containers without a daemon using Podman's rootless container engine.
+
+## When to Use This Skill
+
+Use this skill when:
+- Running containers without root privileges
+- Managing containers on systems without Docker
+- Creating pod-based container groups
+- Using systemd for container management
+- Working in security-conscious environments
+
+## Prerequisites
+
+- Podman installed (4.x+)
+- For rootless: user namespaces enabled
+- Basic container concepts understanding
+
+## Key Differences from Docker
+
+| Feature | Docker | Podman |
+|---------|--------|--------|
+| Architecture | Client-daemon | Daemonless |
+| Root required | Default | Optional (rootless) |
+| Pod support | No | Yes (Kubernetes-style) |
+| Systemd integration | Limited | Native |
+| Socket | docker.sock | podman.sock (optional) |
+
+## Basic Commands
+
+### Container Operations
+
+```bash
+# Run container (identical to Docker)
+podman run -d --name webserver -p 8080:80 nginx
+
+# List containers
+podman ps -a
+
+# Stop and remove
+podman stop webserver
+podman rm webserver
+
+# Execute command
+podman exec -it webserver /bin/sh
+
+# View logs
+podman logs -f webserver
+```
+
+### Image Management
+
+```bash
+# Pull image
+podman pull docker.io/library/nginx:latest
+
+# List images
+podman images
+
+# Build image
+podman build -t myapp:latest .
+
+# Push to registry
+podman push myapp:latest registry.example.com/myapp:latest
+
+# Remove image
+podman rmi nginx:latest
+```
+
+## Rootless Containers
+
+### Setup
+
+```bash
+# Check user namespace support
+cat /proc/sys/user/max_user_namespaces
+
+# Enable if needed (as root)
+echo "user.max_user_namespaces=28633" | sudo tee /etc/sysctl.d/userns.conf
+sudo sysctl -p /etc/sysctl.d/userns.conf
+
+# Configure subuid/subgid for user
+sudo usermod --add-subuids 100000-165535 --add-subgids 100000-165535 $USER
+
+# Verify
+podman unshare cat /proc/self/uid_map
+```
+
+### Running Rootless
+
+```bash
+# Run as regular user (no sudo)
+podman run -d --name myapp -p 8080:80 nginx
+
+# Check user namespace mapping
+podman unshare id
+
+# Verify non-root
+podman top myapp user
+```
+
+### Port Considerations
+
+```bash
+# Rootless cannot bind to ports < 1024 by default
+# Use ports >= 1024
+podman run -d -p 8080:80 nginx
+
+# Or enable unprivileged ports (as root)
+echo "net.ipv4.ip_unprivileged_port_start=80" | sudo tee /etc/sysctl.d/ports.conf
+sudo sysctl -p /etc/sysctl.d/ports.conf
+```
+
+## Pods
+
+### Creating Pods
+
+```bash
+# Create pod
+podman pod create --name mypod -p 8080:80 -p 5432:5432
+
+# Add containers to pod
+podman run -d --pod mypod --name web nginx
+podman run -d --pod mypod --name db postgres:15
+
+# List pods
+podman pod ps
+
+# Containers share network namespace
+podman exec web curl localhost:5432
+```
+
+### Pod Management
+
+```bash
+# Start/stop pod (affects all containers)
+podman pod start mypod
+podman pod stop mypod
+
+# Remove pod and containers
+podman pod rm -f mypod
+
+# View pod details
+podman pod inspect mypod
+
+# Generate Kubernetes YAML from pod
+podman generate kube mypod > mypod.yaml
+```
+
+## Systemd Integration
+
+### Generate Systemd Unit
+
+```bash
+# Generate unit file for container
+podman generate systemd --new --name myapp > ~/.config/systemd/user/container-myapp.service
+
+# For pod
+podman generate systemd --new --name mypod --files
+
+# Reload systemd
+systemctl --user daemon-reload
+
+# Enable and start
+systemctl --user enable --now container-myapp.service
+```
+
+### Quadlet (Podman 4.4+)
+
+```ini
+# ~/.config/containers/systemd/webapp.container
+[Container]
+Image=docker.io/library/nginx:latest
+PublishPort=8080:80
+Volume=webapp-data:/usr/share/nginx/html
+
+[Service]
+Restart=always
+
+[Install]
+WantedBy=default.target
+```
+
+```bash
+# Reload to generate service
+systemctl --user daemon-reload
+
+# Start the service
+systemctl --user start webapp
+```
+
+## Compose Compatibility
+
+### Using Podman Compose
+
+```bash
+# Install podman-compose
+pip install podman-compose
+
+# Run compose file
+podman-compose up -d
+
+# Or use Docker Compose with Podman socket
+systemctl --user enable --now podman.socket
+export DOCKER_HOST=unix:///run/user/$UID/podman/podman.sock
+docker-compose up -d
+```
+
+### Native Podman Kube
+
+```bash
+# Play Kubernetes YAML
+podman kube play deployment.yaml
+
+# Stop and remove
+podman kube down deployment.yaml
+```
+
+## Networking
+
+### Network Management
+
+```bash
+# Create network
+podman network create mynetwork
+
+# Run on network
+podman run -d --network mynetwork --name app myapp
+
+# Connect container to network
+podman network connect mynetwork existing-container
+
+# List networks
+podman network ls
+
+# Inspect network
+podman network inspect mynetwork
+```
+
+### DNS Resolution
+
+```bash
+# Containers on same network can resolve by name
+podman run -d --network mynetwork --name db postgres:15
+podman run -d --network mynetwork --name app \
+  -e DATABASE_HOST=db myapp
+```
+
+## Storage
+
+### Volume Management
+
+```bash
+# Create volume
+podman volume create mydata
+
+# Use volume
+podman run -d -v mydata:/data myapp
+
+# List volumes
+podman volume ls
+
+# Inspect volume
+podman volume inspect mydata
+
+# Rootless volumes location
+ls ~/.local/share/containers/storage/volumes/
+```
+
+### Bind Mounts
+
+```bash
+# Bind mount with SELinux label
+podman run -v ./data:/app/data:Z myapp
+
+# Z = private label (single container)
+# z = shared label (multiple containers)
+```
+
+## Registry Configuration
+
+### Configure Registries
+
+```bash
+# Edit registries.conf
+# ~/.config/containers/registries.conf
+```
+
+```toml
+unqualified-search-registries = ["docker.io", "quay.io"]
+
+[[registry]]
+prefix = "docker.io"
+location = "docker.io"
+
+[[registry.mirror]]
+location = "mirror.gcr.io"
+```
+
+### Authentication
+
+```bash
+# Login to registry
+podman login docker.io
+
+# Login to private registry
+podman login registry.example.com
+
+# Credentials stored in
+# ~/.config/containers/auth.json
+```
+
+## Building Images
+
+### Buildah Integration
+
+```bash
+# Podman uses Buildah for builds
+podman build -t myapp:latest .
+
+# Build with specific format
+podman build --format docker -t myapp .
+
+# Multi-stage build
+podman build --target production -t myapp:prod .
+```
+
+### Buildah Commands
+
+```bash
+# Create container from scratch
+buildah from scratch
+buildah copy working-container ./app /app
+buildah config --entrypoint '["/app/main"]' working-container
+buildah commit working-container myapp:minimal
+```
+
+## Common Issues
+
+### Issue: Permission Denied
+**Problem**: Cannot access files in mounted volumes
+**Solution**: Use `:Z` or `:z` suffix for SELinux, or check ownership
+
+### Issue: Cannot Connect to Container
+**Problem**: Port not accessible in rootless mode
+**Solution**: Use ports >= 1024 or configure unprivileged port start
+
+### Issue: Slow Image Pulls
+**Problem**: Images download slowly
+**Solution**: Configure registry mirrors in registries.conf
+
+### Issue: Systemd Service Fails
+**Problem**: Container doesn't start via systemd
+**Solution**: Enable lingering: `loginctl enable-linger $USER`
+
+## Best Practices
+
+- Use rootless mode for enhanced security
+- Leverage pods for related containers
+- Generate systemd units for production
+- Use Quadlet for declarative container services
+- Configure SELinux labels for bind mounts
+- Enable user lingering for persistent services
+- Use podman auto-update for automatic updates
+- Alias `docker` to `podman` for compatibility
+
+## Related Skills
+
+- [docker-management](../docker-management/) - Docker fundamentals
+- [kubernetes-ops](../../orchestration/kubernetes-ops/) - K8s orchestration
+- [container-hardening](../../../security/hardening/container-hardening/) - Security