Gain insights into Docker fundamentals, delve into advanced concepts like database connectivity and Docker Compose, and discover how to monitor and scale services with Docker Swarm.

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Whether you are a DevOps beginner or just a developer who wants to start working with containers, you’re in the right place. Docker is an in-demand technology that you will be exposed to frequently while on the job.

 

Docker is used for setting up, deploying, and running applications, at scale, by containerizing them. More on that later. Docker also provides developers with a consistent environment for product development, and along with Kubernetes, makes managing the development lifecycle a breeze.

 

In this course, you will learn the fundamentals of Docker such as containers, images, and commands. You’ll then progress to more advanced concepts like connecting to a database container and how to simplify workflows with Docker Compose. At the end, you’ll learn how to monitor clusters and scale Docker services with Swarm.

Working with Containers: Docker & Docker Compose

Let's discuss some of the commands that Compose provides us to use with Compose files.

To be focused on implementation and keep what we learn within the scope of this course, we will only look at frequently-used commands.

# Docker-compose commands

## docker-compose
Every command starts with this. Anything you want to do in Compose, you have to do with commands starting with docker-compose. `docker-compose --help` will give you a list of commands provided in the installed version of docker-compose.

```
$ docker-compose --help
Define and run multi-container applications with Docker.

Usage:
  docker-compose [-f <arg>...] [options] [COMMAND] [ARGS...]
  docker-compose -h|--help

Options:
  -f, --file FILE             Specify an alternate compose file
                              (default: docker-compose.yml)
  -p, --project-name NAME     Specify an alternate project name
                              (default: directory name)
  --verbose                   Show more output
  --log-level LEVEL           Set log level (DEBUG, INFO, WARNING, ERROR, CRITICAL)
  --no-ansi                   Do not print ANSI control characters
  -v, --version               Print version and exit
  -H, --host HOST             Daemon socket to connect to

  --tls                       Use TLS; implied by --tlsverify
  --tlscacert CA_PATH         Trust certs signed only by this CA
  --tlscert CLIENT_CERT_PATH  Path to TLS certificate file
  --tlskey TLS_KEY_PATH       Path to TLS key file
  --tlsverify                 Use TLS and verify the remote
  --skip-hostname-check       Don't check the daemon's hostname against the
                              name specified in the client certificate
  --project-directory PATH    Specify an alternate working directory
                              (default: the path of the Compose file)
  --compatibility             If set, Compose will attempt to convert keys
                              in v3 files to their non-Swarm equivalent
  --env-file PATH             Specify an alternate environment file

Commands:
  build              Build or rebuild services
  config             Validate and view the Compose file
  create             Create services
  down               Stop and remove containers, networks, images, and volumes
  events             Receive real time events from containers
  exec               Execute a command in a running container
  help               Get help on a command
  images             List images
  kill               Kill containers
  logs               View output from containers
  pause              Pause services
  port               Print the public port for a port binding
  ps                 List containers
  pull               Pull service images
  push               Push service images
  restart            Restart services
  rm                 Remove stopped containers
  run                Run a one-off command
  scale              Set number of containers for a service
  start              Start services
  stop               Stop services
  top                Display the running processes
  unpause            Unpause services
  up                 Create and start containers
  version            Show the Docker-Compose version information
```

>`docker-compose <command> --help` will provide you additional information about arguments and implementation details of the command.

## docker-compose build

This command builds images of the mentioned services in the docker-compose.yml file **for which a Dockerfile is provided**.

Carefully read the statement above. The job of the 'build' command is to get the images ready to create containers. If a service is using the prebuilt image, it will skip that service.

```
$ docker-compose build
database uses an image, skipping
Building web
Step 1/11 : FROM python:3.9-rc-buster
 ---> 2e0edf7d3a8a
Step 2/11 : RUN apt-get update && apt-get install -y docker.io
``` 

## docker-compose images

This command lists images built using the current docker-compose file.

```
$ docker-compose images
          Container                  Repository        Tag       Image Id       Size  
--------------------------------------------------------------------------------------
7001788f31a9_docker_database_1   mysql/mysql-server   5.7      2a6c84ecfcb2   333.9 MB
docker_database_1                mysql/mysql-server   5.7      2a6c84ecfcb2   333.9 MB
docker_web_1                     <none>               <none>   d986d824dae4   953 MB
```

## docker-compose run <service>

Similar to `docker run` command, this one creates containers from images built for the services mentioned in the compose file.
It runs a specific service provided as an argument to the command.

```
$ docker-compose run web
Starting 7001788f31a9_docker_database_1 ... done
 * Serving Flask app "app.py" (lazy loading)
 * Environment: development
 * Debug mode: on
 * Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)
 * Restarting with stat
 * Debugger is active!
 * Debugger PIN: 116-917-688
``` 

If you look at the output closely, you'll notice that the database service also started without being mentioned in the command. That's because the web service is dependent on the database service. So, it will start all the dependent services and then, the mentioned service.

## docker-compose up

This does the job of the `docker-compose build` and `docker-compose run` commands. It initially builds the images if they are not located locally and then starts the containers.

If images are already built, it will fork the container directly. We can force it to rebuild the image by adding a `--build` argument.

```
$ docker-compose up
Creating docker_database_1 ... done
Creating docker_web_1      ... done
Attaching to docker_database_1, docker_web_1
database_1  | [Entrypoint] MySQL Docker Image 5.7.29-1.1.15
database_1  | [Entrypoint] Initializing database
web_1       |  * Serving Flask app "app.py" (lazy loading)
web_1       |  * Environment: development
web_1       |  * Debug mode: on
web_1       |  * Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)
web_1       |  * Restarting with stat
web_1       |  * Debugger is active!
web_1       |  * Debugger PIN: 855-188-665
database_1  | [Entrypoint] Database initialized
database_1  | Warning: Unable to load '/usr/share/zoneinfo/iso3166.tab' as time zone. Skipping it.
```

## docker-compose stop
This command stops the running containers of the specified services in the docker-compose file.

```
$ docker-compose stop
Stopping docker_web_1      ... done
Stopping docker_database_1 ... done
```
## docker-compose rm

This command removes the containers of the services or the containers created using the current docker-compose file. It can be containers created using the `docker-compose run` command or the `docker-compose up` command.
It will remove all the containers which have services mentioned in the docker-compose file.

```
$ docker-compose rm
Going to remove docker_web_1, docker_database_1
Are you sure? [yN] y
Removing docker_web_1      ... done
Removing docker_database_1 ... done
```

## docker-compose start
This command starts any stopped containers of the services. If all the containers are already up and running, they will just inform that all containers are starting and exit with 0 status.

```
$ docker-compose start
Starting database ... done
Starting web      ... done
```

## docker-compose restart

This command restarts all the containers of the services. 

```
$ docker-compose restart
Restarting docker_web_1      ... done
Restarting docker_database_1 ... done
```

## docker-compose ps

This lists all the containers for services mentioned in the current docker-compose file. The containers can either be running or stopped.

```
$ docker-compose ps
      Name                 Command             State               Ports         
---------------------------------------------------------------------------------
docker_database_1   /entrypoint.sh mysqld   Up (healthy)   3306/tcp, 33060/tcp   
docker_web_1        flask run               Up             0.0.0.0:5000->5000/tcp

$ docker-compose ps
      Name                 Command          State    Ports
----------------------------------------------------------
docker_database_1   /entrypoint.sh mysqld   Exit 0        
docker_web_1        flask run               Exit 0        
```

## docker-compose down

This command is similar to `docker system prune`. However, there is a small difference. It stops all the services and then cleans up the containers, networks, and images used and created by the compose file services.

```
$ docker-compose down
Removing docker_web_1      ... done
Removing docker_database_1 ... done
Removing network docker_default
(django-tuts) Venkateshs-MacBook-Air:Docker venkateshachintalwar$ docker-compose images
Container   Repository   Tag   Image Id   Size
----------------------------------------------
(django-tuts) Venkateshs-MacBook-Air:Docker venkateshachintalwar$ docker-compose ps
Name   Command   State   Ports
------------------------------
```

## docker-compose logs

This command is similar to `docker logs <container ID>`. The small difference is this prints all the logs created by all the services. We can also use the `-f` argument to see real-time logs.

```
$ docker-compose logs
Attaching to docker_web_1, docker_database_1
database_1  | [Entrypoint] MySQL Docker Image 5.7.29-1.1.15
database_1  | [Entrypoint] Initializing database
database_1  | [Entrypoint] Database initialized
database_1  | Warning: Unable to load '/usr/share/zoneinfo/iso3166.tab' as time zone. Skipping it.
database_1  | Warning: Unable to load '/usr/share/zoneinfo/leapseconds' as time zone. Skipping it.
web_1       |  * Serving Flask app "app.py" (lazy loading)
web_1       |  * Environment: development
web_1       |  * Debug mode: on
web_1       |  * Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)
web_1       |  * Restarting with stat
web_1       |  * Debugger is active!
web_1       |  * Debugger PIN: 290-944-777
```


A brief overview of Docker Compose commands

Docker-Compose Commands Overview

Introduction to Course

Why Docker?

Getting Started With Docker

Docker Fundamentals

Automation using Dockerfile

Advance Docker

Introduction to Docker-Compose

Exposure to Docker Swarm

Bonus Section

Docker-Compose Commands Overview

Docker-compose commands

docker-compose