Bash Automation Blueprint

These scripts automate common Docker maintenance tasks. Copy, adapt, and schedule them for your environment.

Health Check Script

Monitor all running containers and alert on unhealthy ones:

#!/usr/bin/env bash
set -euo pipefail

echo "=== Docker Health Check: $(date) ==="

# Check if Docker daemon is running
if ! docker info &>/dev/null; then
    echo "CRITICAL: Docker daemon is not running!"
    exit 1
fi

# Check each running container
UNHEALTHY=0
while IFS= read -r container; do
    NAME=$(docker inspect "$container" --format '{{.Name}}' | sed 's/\///')
    STATUS=$(docker inspect "$container" --format '{{.State.Status}}')
    HEALTH=$(docker inspect "$container" --format '{{if .State.Health}}{{.State.Health.Status}}{{else}}no-healthcheck{{end}}')
    RESTARTS=$(docker inspect "$container" --format '{{.RestartCount}}')
    OOM=$(docker inspect "$container" --format '{{.State.OOMKilled}}')

    # Flag issues
    if [[ "$HEALTH" == "unhealthy" ]] || [[ "$OOM" == "true" ]] || [[ "$RESTARTS" -gt 5 ]]; then
        echo "WARNING: $NAME | status=$STATUS health=$HEALTH restarts=$RESTARTS oom=$OOM"
        UNHEALTHY=$((UNHEALTHY + 1))
    else
        echo "OK:      $NAME | status=$STATUS health=$HEALTH restarts=$RESTARTS"
    fi
done < <(docker ps -q)

echo ""
echo "Total containers: $(docker ps -q | wc -l)"
echo "Issues found: $UNHEALTHY"

exit $UNHEALTHY

Disk Usage Monitor

Check disk usage and warn when thresholds are exceeded:

#!/usr/bin/env bash
set -euo pipefail

WARN_THRESHOLD=70   # Warn at 70% disk usage
CRIT_THRESHOLD=85   # Critical at 85%

echo "=== Docker Disk Monitor: $(date) ==="

# Host disk usage for Docker data directory
DISK_USAGE=$(df /var/lib/docker --output=pcent | tail -1 | tr -d '% ')

if [[ "$DISK_USAGE" -ge "$CRIT_THRESHOLD" ]]; then
    echo "CRITICAL: Docker disk at ${DISK_USAGE}%"
    echo "Run: docker system prune -f"
elif [[ "$DISK_USAGE" -ge "$WARN_THRESHOLD" ]]; then
    echo "WARNING: Docker disk at ${DISK_USAGE}%"
else
    echo "OK: Docker disk at ${DISK_USAGE}%"
fi

# Docker-specific breakdown
echo ""
docker system df

Safe Cleanup Script

Remove old resources with safety checks:

#!/usr/bin/env bash
set -euo pipefail

DRY_RUN=${1:-"--dry-run"}

echo "=== Docker Cleanup: $(date) ==="
echo "Mode: $DRY_RUN"
echo ""

# Show current usage
echo " Current Usage "
docker system df
echo ""

if [[ "$DRY_RUN" == "--execute" ]]; then
    echo " Cleaning "
    
    # Safe operations first
    docker container prune -f
    docker image prune -f
    docker network prune -f
    docker builder prune -f
    
    echo ""
    echo " After Cleanup "
    docker system df
else
    echo " Would Remove "
    echo "Stopped containers:  $(docker ps -aq -f status=exited | wc -l)"
    echo "Dangling images:     $(docker images -f dangling=true -q | wc -l)"
    echo "Unused networks:     $(docker network ls -f dangling=true -q 2>/dev/null | wc -l)"
    echo ""
    echo "Run with --execute to perform cleanup"
    echo "NOTE: Volumes are NOT pruned by this script (data safety)"
fi

Usage:

# Preview what would be cleaned
bash cleanup.sh

# Actually clean
bash cleanup.sh --execute

Container Resource Snapshot

Capture a point-in-time resource report:

#!/usr/bin/env bash
set -euo pipefail

REPORT_FILE="docker-report-$(date +%Y%m%d-%H%M%S).txt"

{
    echo "=== Docker Resource Report ==="
    echo "Generated: $(date)"
    echo "Host: $(hostname)"
    echo ""

    echo " Docker Version "
    docker version --format '{{.Server.Version}}'
    echo ""

    echo " Disk Usage "
    docker system df
    echo ""

    echo " Running Containers "
    docker ps --format 'table {{.Names}}\t{{.Status}}\t{{.Image}}\t{{.Ports}}'
    echo ""

    echo " Resource Usage "
    docker stats --no-stream --format 'table {{.Name}}\t{{.CPUPerc}}\t{{.MemUsage}}\t{{.MemPerc}}'
    echo ""

    echo " Images "
    docker images --format 'table {{.Repository}}\t{{.Tag}}\t{{.Size}}\t{{.CreatedSince}}'
    echo ""

    echo " Volumes "
    docker volume ls
} > "$REPORT_FILE"

echo "Report saved to: $REPORT_FILE"

Scheduling with Cron

# Edit crontab
crontab -e

# Health check every 5 minutes
*/5 * * * * /opt/scripts/docker-health.sh >> /var/log/docker-health.log 2>&1

# Disk monitor every hour
0 * * * * /opt/scripts/docker-disk.sh >> /var/log/docker-disk.log 2>&1

# Safe cleanup weekly (Sunday 3 AM)
0 3 * * 0 /opt/scripts/docker-cleanup.sh --execute >> /var/log/docker-cleanup.log 2>&1

# Resource report daily
0 6 * * * /opt/scripts/docker-report.sh

Key Takeaways

• Use dry-run mode for cleanup scripts before executing in production.
• Schedule health checks and disk monitoring with cron.
• Never auto-prune volumes -- the cleanup script above intentionally skips them.
• Save resource reports for trend analysis and capacity planning.

What's Next

• Continue to Python Audit and Reporting.