docker-compose cheat sheet

docker-compose cheat sheet

#=====================================================================

services:        # Define the services (containers) in this Compose file
  nagios:        # Service name: nagios
    image: nagios459-debian12:latest  # Use the pre-built Nagios Debian 12 image
    container_name: nagios             # Assign a custom container name for easier reference
    restart: unless-stopped            # Restart policy: restart container unless explicitly stopped
    environment:                       # Define environment variables for the container
      NAGIOS_FQDN: nagios.example.com # Fully Qualified Domain Name for Nagios
      NAGIOSADMIN_USER: nagiosadmin   # Admin username for Nagios web interface
      NAGIOSADMIN_PASS: nagios        # Admin password for Nagios web interface
      DEBIAN_FRONTEND: noninteractive # Avoid interactive prompts during apt installs
    ports:                             # Map container ports to host ports
      - "80:80"      # Host port 80 → container port 80 for Nagios web interface
      - "5667:5667"  # Host port 5667 → container port 5667 for NRPE checks
    volumes:                           # Mount persistent volumes to container paths
      - nagios_var:/opt/nagios/var            # Nagios runtime data
      - nagios_etc:/opt/nagios/etc            # Nagios configuration files
      - apache_logs:/var/log/apache2          # Apache log files
      - nagios_plugins:/opt/Custom-Nagios-Plugins # Custom Nagios plugins
      - nagiosgraph_var:/opt/nagiosgraph/var # NagiosGraph runtime data
      - nagiosgraph_etc:/opt/nagiosgraph/etc # NagiosGraph configuration files
    tty: true                           # Allocate a pseudo-TTY (useful for interactive shell)
    stdin_open: true                    # Keep STDIN open for interactive sessions

volumes:                                # Define named Docker volumes (persistent storage)
  nagios_var:                            # Volume for Nagios runtime data
  nagios_etc:                            # Volume for Nagios configuration
  apache_logs:                           # Volume for Apache logs
  nagios_plugins:                        # Volume for custom Nagios plugins
  nagiosgraph_var:                       # Volume for NagiosGraph runtime data
  nagiosgraph_etc:                       # Volume for NagiosGraph configuration

#=====================================================================
You’re using named volumes like nagios_var, nagios_etc, etc., under the volumes: section.

    Named volumes are managed by Docker, not tied to a specific host directory.

    Docker will automatically create these volumes the first time you run docker-compose up.

Paths inside the container (e.g., /opt/nagios/var) will be populated by Docker when the container starts.

If you wanted to bind a host directory instead of a Docker volume, you would use a host path like:

    volumes:
      - ./nagios_var:/opt/nagios/var

    In that case, the ./nagios_var directory must exist on the host (Docker won’t create it automatically).

✅ Summary: With your current docker-compose.yml using named volumes, Docker handles creation automatically. You can just run:

docker-compose -f docker-compose.yml.debian up -d

and it will create the necessary volumes and start the Nagios container.

#=====================================================================
# 1️⃣ Build the image from the Dockerfile
docker-compose -f docker-compose.yml.debian build
# -f docker-compose.yml.debian : specify the Compose file
# build : build the Docker image defined in the Compose file
# This step creates the 'nagios459-debian12:latest' image if not already built

# 2️⃣ Start the container in detached mode
docker-compose -f docker-compose.yml.debian up -d
# up : start the services defined in the Compose file
# -d : run in detached mode (in background)
# Creates and starts the 'nagios' container, applies volumes, environment variables, and port mappings

# 3️⃣ View container logs (optional)
docker-compose -f docker-compose.yml.debian logs -f nagios
# logs -f : follow the logs in real-time
# nagios : view logs of the Nagios service

# 4️⃣ Access an interactive shell inside the running container
docker-compose -f docker-compose.yml.debian exec nagios bash
# exec : execute a command inside a running container
# bash : start a Bash shell for manual inspection or troubleshooting

# 5️⃣ Stop the container
docker-compose -f docker-compose.yml.debian stop
# stop : stop the running container gracefully
# Container still exists on disk, volumes are preserved

# 6️⃣ Restart the container (if needed)
docker-compose -f docker-compose.yml.debian restart
# restart : stop and immediately start the container again

# 7️⃣ Remove the container without deleting volumes
docker-compose -f docker-compose.yml.debian rm -f nagios
# rm : remove the container
# -f : force removal without confirmation
# Volumes are preserved unless explicitly removed

# 8️⃣ Tear down everything including networks and optionally volumes
docker-compose -f docker-compose.yml.debian down -v
# down : stop and remove containers, networks, and default Docker Compose setup
# -v : also remove associated named volumes
# Use this to completely reset the environment

#=====================================================================
Docker Compose Commands

    Build the image (if you want Compose to build from Dockerfile):

docker-compose -f docker-compose.yml.debian build

    Since you already built nagios459-debian12:latest, this step is optional unless you change the Dockerfile.

    Start container:

docker-compose -f docker-compose.yml.debian up -d

    -d → detached mode (runs in background).

    View logs (Nagios output, Apache logs):

docker-compose -f docker-compose.yml.debian logs -f

    Stop container:

docker-compose -f docker-compose.yml.debian stop

    Restart container:

docker-compose -f docker-compose.yml.debian restart

    Destroy container and volumes:

docker-compose -f docker-compose.yml.debian down -v

    -v deletes all associated volumes (nagios_var, nagios_etc, etc.)

    down removes the container and network created by Compose.

Extra Tips

    To enter the container interactively:

docker exec -it nagios bash

    To rebuild after Dockerfile changes:

docker-compose -f docker-compose.yml.debian build --no-cache
docker-compose -f docker-compose.yml.debian up -d
#=====================================================================
 To clean up all dangling images:

Run:

docker image prune

You'll be prompted to confirm.

To skip the prompt:

docker image prune -f

If you only want to remove dangling images (those with <none> tag):

docker images -f "dangling=true"

To delete them:

docker rmi $(docker images -f "dangling=true" -q)

If any containers are still using these images (even stopped ones), Docker will refuse to delete them.

To check if an image is still in use:

docker ps -a --filter "ancestor=<IMAGE_ID>"


 Best Practice for Local Dev Environments

    Use docker compose down --volumes to reset state only when needed.

    Use docker volume prune regularly to clean up dangling volumes.

    Use docker image prune -a or docker builder prune to clean up old images/cache.
#=====================================================================
ports:
  - target: 8000
    published: 7778
    protocol: tcp

target: 8000 = the internal port inside the container where LibreNMS runs its web server.

published: 7778 = the external host port you want to expose to access LibreNMS in the browser.

This maps http://<your-host>:7778 → container's :8000.
#=====================================================================
Restart containers after changes
docker compose down -v
docker compose up -d --build

Rebuild and restart the container

From the top-level directory where docker-compose.yml is:

docker compose down
docker compose build librenms
docker compose up 
#=====================================================================
docker volume rm librenms-logs

Option 3: Check for processes locking the volume on host

If you use a bind mount or named volume mapped to host directory, check if some host process (e.g. another container or file handle) is locking the directory.

On Linux, you can check:

lsof +D /path/to/mounted/logs
#=====================================================================
If you want to clean up orphan containers, run:

docker compose down --remove-orphans -v
#=====================================================================
Why the user and data persisted despite docker compose down -v

Even though you used docker compose down -v (which does delete named or anonymous volumes created by Docker Compose), your docker-compose.yml includes this line

volumes:
  - "./librenms:/data"

The ./librenms folder on your host stores LibreNMS data.

When you did docker compose down -v, Docker:

    Removed volumes it manages (like the db volume, if it's named).

    Did not touch bind-mounted folders like ./librenms.

So when you brought the containers up again with docker compose up -d --build, the container saw:

    "Oh, the /data directory already has previous config, users, etc."
    
    
#=====================================================================
docker compose exec librenms mysql -h db -u librenms -p

#=====================================================================

$ docker compose up -d --build

#=====================================================================

docker compose up -d --build
write /var/lib/docker/tmp/GetImageBlob1490303091: no space left on device

df -h
/dev/sda8        71G   11G   57G  16% /home
/dev/sda5       6.4G  6.3G     0 100% /var

explain how to fix this, there is much space on /home

Docker stores all its images, containers, volumes, and temporary files under /var/lib/docker by default. Since /var is a small (6.4 GB) and full partition, Docker cannot proceed — even though /home has plenty of space

Solution: Move Docker storage to /home

We will move Docker's storage location from /var/lib/docker to /home/docker-data (or another directory with more space).

tep-by-step Instructions
1. Stop Docker

sudo systemctl stop docker

2. Create a new directory on /home

sudo mkdir -p /home/docker-data

3. Move existing Docker data (if any)

sudo rsync -aP /var/lib/docker/ /home/docker-data/

4. Configure Docker to use the new location

Create or edit Docker’s daemon config:

sudo mkdir -p /etc/docker
sudo nano /etc/docker/daemon.json

Add:

{
  "data-root": "/home/docker-data"
}

5. Restart Docker

sudo systemctl start docker

6. Verify

Run:

docker info | grep "Docker Root Dir"

You should see:

Docker Root Dir: /home/docker-data

💡 Optional: Clean up old data

Once you're sure everything works, you can delete the old directory:

sudo rm -rf /var/lib/docker

#=====================================================================
docker compose -f docker-compose.json up #use JSON instead of YAML compose file
#=====================================================================
docker compose -f ~/hello_world/docker-compose.yml build
docker compose -f ~/hello_world/docker-compose.yml up -d
docker compose ps # Lists containers.
docker compose stop
docker compose start # Starts existing containers for a service.
docker compose stop # Stops running containers without removing them.
docker compose pause # Pauses running containers of a service.
docker compose unpause # Unpauses paused containers of a service
docker compose up #Builds, (re)creates, starts, and attaches to containers for a service
docker compose up -d #Create docker image and run container in the background
docker compose down # Stops containers and removes containers, networks, volumes, and images created by up.
docker compose down -v # tear down the containers and volumes
docker compose --version
docker compose ps
docker compose images #List images used by the created containers
docker compose stop
docker compose run web
docker compose down
	
docker compose -f docker-compose-dev.yml up -d app1
docker compose -f docker-compose-test-local.yml run --rm unit
docker compose -f docker-compose-test-local.yml build app -> as an alternative, define build arguments inside a Docker Compose file
docker compose build

docker compose config

docker compose -f docker-compose-test-local.yml up -d staging-dep
docker compose -f docker-compose-test-local.yml ps
docker compose -f docker-compose-test-local.yml run --rm staging
docker compose -f docker-compose-test-local.yml down
docker compose -f docker-compose-local.yml up -d registry
#=====================================================================
docker compose logs
docker compose logs -f initializer #track progress
docker compose logs initializer | grep "Admin password:" #obtain admin credentials

stream logs in real-time, use the -f (follow) flag:
docker compose -f librenms/docker-master/examples/compose/compose.yml logs -f

limit the number of lines displayed using the --tail option
docker compose -f librenms/docker-master/examples/compose/compose.yml logs --tail=100

docker compose -f librenms/docker-master/examples/compose/compose.yml logs --timestamps

for a specific service
docker compose -f librenms/docker-master/examples/compose/compose.yml logs --timestamps web

View logs for all services
docker-compose logs

View logs for Nginx (web)
docker-compose logs web

save logs for analysis, redirect output
docker-compose logs web > web_logs.txt

Checking Logs of a Specific Container
docker ps
docker logs -f <container_id>

Use docker compose logs -f librenms-app to monitor LibreNMS logs.
docker logs librenms-app
docker logs librenms-app --tail 50 --follow


#=====================================================================
docker compose up -d #Create docker image and run container in the background
docker compose exec kali /bin/bash #Create docker image and run container in the background
#=====================================================================
docker build -t kalicmd . --file=/vagrant/dockerfiles/kalilinux/toolkali
docker compose --file /vagrant/dockerfiles/kalilinux/docker-compose.yml run kali-service
docker compose --file /vagrant/dockerfiles/kalilinux/docker-compose.yml ps #Lists containers

cat docker-compose.yml
version: '3'
services:
  kali-service:
    image: "kalicmd"
    volumes:
      - /mnt/share-kali:/share
      - /mnt/share-kali/.bash_history:/root/.bash_history
#=====================================================================
docker compose build --no-cache #Force the execution of each step/instruction in the Dockerfile
docker compose build --no-cache && docker compose up -d --force-recreate #t recreate all containers
docker build --pull --no-cache --tag myimage:version #force rebuilding of layers already available
#=====================================================================
#=====================================================================
WINDOWS
#=====================================================================
docker compose version
#=====================================================================
#=====================================================================
#=====================================================================
#=====================================================================
#environment variable, non-default dockere file name
#docker-compose.yaml
version: '3.8'
services:
  myservice:
    build:
      context: .
      dockerfile: ./docker/Dockerfile.myservice
    image: myself/myservice
    env_file:
     - ./var.env
    environment:
     - VAR_C=C
     - VAR_D=D
    volumes:
     - $HOME/myfolder:/myfolder
    ports:
     - "5000:5000"

#=====================================================================
cat Dockerfile.test
cat docker-compose.test.yml
docker compose -f ~/hello_world/docker-compose.test.yml -p ci build
docker compose -f ~/hello_world/docker-compose.test.yml -p ci up -d
docker compose -p ci stop
#=====================================================================
                  Docker Compose v2	          Docker compose v3
 Multi-host	      No	                        Yes                  
 Start services	  docker compose up -d	      docker stack deploy --compose-file=docker-compose.yml  
 Scale service	  docker compose scale =	    docker service scale =
 Shutdown	        docker compose down	        docker stack rm

#=====================================================================
# docker-compose.yml
version: '3'

services:
  web:
    build: .
    # build from Dockerfile
    context: ./Path
    dockerfile: Dockerfile
    ports:
     - "5000:5000"
    volumes:
     - .:/code
  redis:
    image: redis
#=====================================================================
# Builds, (re)creates, starts, and attaches to containers for a service.
docker compose up
# Stops containers and removes containers, networks, volumes, and images created by up.
docker compose down
#=====================================================================
web:
  # build from Dockerfile
  build: .
#=====================================================================
  # build from custom Dockerfile
  build:
    context: ./dir
    dockerfile: Dockerfile.dev
#=====================================================================
  # build from image
  image: ubuntu
#=====================================================================
ports:
    - "3000"
    - "8000:80"  # guest:host
#=====================================================================
  # expose ports to linked services (not to host)
  expose: ["3000"]
#=====================================================================
# command to execute
  command: bundle exec thin -p 3000
  command: [bundle, exec, thin, -p, 3000]
#=====================================================================
  # override the entrypoint
  entrypoint: /app/start.sh
  entrypoint: [php, -d, vendor/bin/phpunit]
#=====================================================================
  volumes:
    - /var/lib/mysql
    - ./_data:/var/lib/mysql

version: '2'
  services:
    cms:
       image: <IMAGE>:<TAG>
       ports:
       - <LOCAL_PORT>:<CONTAINER_PORT>
       volumes:
       - <LOCAL_PATH>:<CONTAINER_PATH>
       
#=====================================================================
# join a pre-existing network
networks:
  default:
    external:
      name: frontend
#=====================================================================
# creates a custom network called `frontend`
networks:
  frontend:
#=====================================================================
  # makes the `db` service available as the hostname `database`
  # (implies depends_on)
  links:
    - db:database
    - redis
#=====================================================================
  # make sure `db` is alive before starting
  depends_on:
    - db
#=====================================================================
services:
  web:
    dns: 8.8.8.8
    dns:
      - 8.8.8.8
      - 8.8.4.4
#=====================================================================
a Bash script to automate the creation of a superuser for NetBox using Docker Compose. It uses the provided username, email, and password, and bypasses the password validation prompt.

#!/bin/bash

# Variables
USERNAME="admin"
EMAIL="[email protected]"
PASSWORD="Netbox2025!"

# Run the createsuperuser command non-interactively
sudo docker compose -f netbox-docker/docker-compose.yml exec netbox /opt/netbox/netbox/manage.py createsuperuser \
    --username "$USERNAME" \
    --email "$EMAIL" \
    --no-input || true

# Set password using Django shell
sudo docker compose -f netbox-docker/docker-compose.yml exec netbox /opt/netbox/netbox/manage.py shell -c "
from django.contrib.auth import get_user_model;
User = get_user_model();
user = User.objects.get(username='$USERNAME');
user.set_password('$PASSWORD');
user.save();
print('✅ Superuser created successfully with provided password.')
"

echo "🎉 NetBox superuser created with username '$USERNAME' and email '$EMAIL'"

#=====================================================================