Container_automation

Chapter 40: Container Automation Scripts

Overview

This chapter covers container automation scripts using Docker and Podman. These scripts are essential for DevOps engineers managing containerized applications.

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Docker Basics

Common Docker Commands

# Container management
docker ps                    # List running containers
docker ps -a               # List all containers
docker run                 # Run a container
docker start              # Start a container
docker stop               # Stop a container
docker rm                 # Remove a container

# Image management
docker images             # List images
docker pull              # Pull an image
docker rmi               # Remove an image
docker build             # Build an image

# Logs and stats
docker logs              # Container logs
docker stats             # Container stats
docker exec              # Execute command in container

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Container Management Scripts

List Containers

#!/usr/bin/env bash
# list_containers.sh - List all containers

docker ps -a --format "table {{.ID}}\t{{.Names}}\t{{.Status}}\t{{.Image}}\t{{.Ports}}"

Container Health Check

#!/usr/bin/env bash
# check_container_health.sh - Check container health

set -euo pipefail

CONTAINER="${1:-}"

if [[ -z "$CONTAINER" ]]; then
    echo "Usage: $0 <container_name>"
    exit 1
fi

# Check if container is running
if docker ps --format '{{.Names}}' | grep -q "^${CONTAINER}$"; then
    echo "Container $CONTAINER is running"

    # Check health status
    health=$(docker inspect --format='{{.State.Health.Status}}' "$CONTAINER" 2>/dev/null || echo "none")
    echo "Health status: $health"

    exit 0
else
    echo "Container $CONTAINER is not running"
    exit 1
fi

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Docker Compose Scripts

Start/Stop Services

#!/usr/bin/env bash
# docker_services.sh - Manage docker-compose services

set -euo pipefail

COMPOSE_FILE="${COMPOSE_FILE:-docker-compose.yml}"
ACTION="${1:-up}"

case "$ACTION" in
    up)
        echo "Starting services..."
        docker-compose -f "$COMPOSE_FILE" up -d
        ;;
    down)
        echo "Stopping services..."
        docker-compose -f "$COMPOSE_FILE" down
        ;;
    restart)
        echo "Restarting services..."
        docker-compose -f "$COMPOSE_FILE" restart
        ;;
    logs)
        echo "Showing logs..."
        docker-compose -f "$COMPOSE_FILE" logs -f
        ;;
    *)
        echo "Usage: $0 {up|down|restart|logs}"
        exit 1
        ;;
esac

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Container Monitoring

Resource Usage

#!/usr/bin/env bash
# container_stats.sh - Show container resource usage

docker stats --no-stream --format "table {{.Name}}\t{{.CPUPerc}}\t{{.MemUsage}}\t{{.NetIO}}\t{{.BlockIO}}"

Container Logs

#!/usr/bin/env bash
# container_logs.sh - View container logs

set -euo pipefail

CONTAINER="${1:-}"
LINES="${2:-100}"

if [[ -z "$CONTAINER" ]]; then
    echo "Usage: $0 <container> [lines]"
    exit 1
fi

docker logs --tail "$LINES" -f "$CONTAINER"

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Image Management

Cleanup Images

#!/usr/bin/env bash
# cleanup_images.sh - Clean up unused Docker images

set -euo pipefail

echo "Cleaning up Docker resources..."

# Remove stopped containers
echo "Removing stopped containers..."
docker container prune -f

# Remove unused images
echo "Removing unused images..."
docker image prune -a -f

# Remove unused volumes
echo "Removing unused volumes..."
docker volume prune -f

# Remove unused networks
echo "Removing unused networks..."
docker network prune -f

echo "Cleanup complete"

Build and Tag

#!/usr/bin/env bash
# build_image.sh - Build and tag Docker image

set -euo pipefail

IMAGE_NAME="${1:-}"
TAG="${2:-latest}"
DOCKERFILE="${3:-Dockerfile}"
CONTEXT="${4:-.}"

if [[ -z "$IMAGE_NAME" ]]; then
    echo "Usage: $0 <image_name> [tag] [dockerfile] [context]"
    exit 1
fi

echo "Building image: $IMAGE_NAME:$TAG"

docker build \
    -t "$IMAGE_NAME:$TAG" \
    -f "$DOCKERFILE" \
    "$CONTEXT"

echo "Image built successfully"

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Docker Registry

Push to Registry

#!/usr/bin/env bash
# push_image.sh - Push image to registry

set -euo pipefail

IMAGE="${1:-}"
REGISTRY="${REGISTRY:-docker.io}"

if [[ -z "$IMAGE" ]]; then
    echo "Usage: $0 <image> [registry]"
    exit 1
fi

echo "Pushing $IMAGE to $REGISTRY..."

docker tag "$IMAGE" "$REGISTRY/$IMAGE"
docker push "$REGISTRY/$IMAGE"

echo "Image pushed successfully"

Pull Latest

#!/usr/bin/env bash
# pull_latest.sh - Pull latest image

set -euo pipefail

IMAGE="${1:-}"

if [[ -z "$IMAGE" ]]; then
    echo "Usage: $0 <image>"
    exit 1
fi

echo "Pulling latest $IMAGE..."

docker pull "$IMAGE"

echo "Image pulled successfully"

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Backup and Restore Containers

Backup Container

#!/usr/bin/env bash
# backup_container.sh - Backup container data

set -euo pipefail

CONTAINER="${1:-}"
BACKUP_DIR="${2:-/tmp/container_backups}"

if [[ -z "$CONTAINER" ]]; then
    echo "Usage: $0 <container> [backup_dir]"
    exit 1
fi

mkdir -p "$BACKUP_DIR"

timestamp=$(date +%Y%m%d_%H%M%S)
backup_file="$BACKUP_DIR/${CONTAINER}_${timestamp}.tar.gz"

echo "Backing up container $CONTAINER..."

docker export "$CONTAINER" | gzip > "$backup_file"

echo "Backup created: $backup_file"

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Multi-Container Management

Deploy Stack

#!/usr/bin/env bash
# deploy_stack.sh - Deploy Docker stack

set -euo pipefail

STACK_NAME="${1:-myapp}"
COMPOSE_FILE="${2:-docker-compose.yml}"

echo "Deploying stack: $STACK_NAME"

docker stack deploy -c "$COMPOSE_FILE" "$STACK_NAME"

echo "Stack deployed successfully"
docker stack ps "$STACK_NAME"

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Health Checks

Container Health Monitor

#!/usr/bin/env bash
# monitor_containers.sh - Monitor container health

set -euo pipefail

ALERT_EMAIL="${ALERT_EMAIL:-admin@example.com}"

check_containers() {
    local unhealthy=0

    for container in $(docker ps --format '{{.Names}}'); do
        health=$(docker inspect --format='{{.State.Health.Status}}' "$container" 2>/dev/null || echo "none")

        if [[ "$health" == "unhealthy" ]]; then
            echo "ALERT: $container is unhealthy"
            ((unhealthy++))
        fi
    done

    if [[ $unhealthy -gt 0 ]]; then
        echo "Sending alert..."
        # Send alert email
        echo "$unhealthy containers are unhealthy" | mail -s "Container Alert" "$ALERT_EMAIL"
        return 1
    fi

    echo "All containers healthy"
    return 0
}

check_containers

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Summary

In this chapter, you learned:

• ✅ Docker basics and common commands
• ✅ Container management scripts
• ✅ Docker Compose automation
• ✅ Container monitoring
• ✅ Image management and cleanup
• ✅ Docker registry operations
• ✅ Container backup and restore
• ✅ Multi-container deployment
• ✅ Health check monitoring

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Next Steps

Continue to the next chapter to learn about Coprocesses.

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