Running example and Docker commands extracted from Server for hackers free series on containers.

# Docker commands

What are images and containers in Docker? To make an analogy with PHP:

images are like classes (ex: SomeClass.php)
containers are like objects (ex: $container = new SomeClass())

Notes: Make sure that the scripts inside a container does not run as a daemon (in the background), keep them in the foreground for Docker to see them and debug (ex: nginx, php).

List all commands and args availabe

$ docker --help

Show available args for a command (ex: ps, images)

$ docker <command-name> --help

List all images

$ docker image ls

List only the images ids

$ docker image ls -q

Remove an image

$ docker image rm <image-name>:<tag-name>

Remove all images $(docker image ls -q) - returns a complete list with all the containers ids

$ docker image rm $(docker image ls -q)

List all containers (including the ones not running) -a - show all the containers

$ docker ps -a

List all running containers

$ docker ps

Stops container with id <container-id> (ex: as5335fsa639ggf) It will also remove it if the container has been started with -rm flag

$ docker stop <container-id>

Remove container with id <container-id> (ex: as5335fsa639ggf)

$ docker rm <container-id>

Create a container from an image
--rm - destroy the container after is done running
-d - run the container in the background
-v $(pwd)/<directory-name>:/var/ww/html - share (symlink/mount/bind) a directory. It shares <directory-name> from the current directory ($(pwd)) and place it in the docker container at /var/ww/html
-p 8080:80 - share port 8080 from localhost to port 80 inside of the container
--name - give the container a name
- e <enviroment-variable-name> - pass a gloabal enviroment variable to the container
--network=<network-name> - join the network that we created called <network-name> (ex: appnet)
-w <path-to/directory-name> - set the current working directory. So, the container will spin up, will cd into this directory and it will run the <command(s)> appended
<image-name> - the image name from which to create the container (ex: rabbitmq, mailhog/mailhog, php)
<command> <args...> (optional) - run this command inside the container after has run (ex: nginx, nginx -g 'daemon off;')

# Note: replace -d with -it to output logs in the console.
$ docker run --rm -d -v $(pwd)/<directory-name>:/var/ww/html -p 8080:80 <image-name>:<image-tag> <command> <args...>

# or on multipe lines.
$ docker run --rm -d \
    -v $(pwd):/application:/var/www/html \
    -p 8080:80 \
    <image-name>:<image-tag> <command> <args...>
    
# example 2: install a project via composer 
$ docker run --rm -d -p 8080:80 -v $(pwd):/var/ww/html -w /var/ww/html <image-name>:<image-tag> composer create-project laravel/laravel <directory-name>
    
# Give the container a name
$ docker run ... --name=mydb

# Pass enviroment variables to the container
$ docker run ... --name=my_db -e MYSQL_ROOT_PASSWORD=secret -e MYSQL_DATABASE=my_datatabse_name

# Join a network ('my_db' will be the container name inside the network)
$ docker run ... --name=my_db --network=appnet

Create a new container and run a service in it
--rm - destroy the container after is done running.
-it - interact with the container (is just like I would ssh into the container...but is not actual ssh)
<image-name> - the image name from which to create the container (ex: ubuntu:18.04)
<service-name> - which service to run in the container after it has started (ex: bash - open bash inside the container, nginx - run nginx inside the container etc.)
-d - run the container in the background

# example of service names: bash, php, nginx
$ docker run --rm -it <image-name> <service-name>

# example 1: running a container in the background and start nginx 
$ docker run -d <image-name> nginx

Execute a command inside a running container
-it - interact with the container (is just like I would ssh into the container...but is not actual ssh)
<container-id> (or <host-name> ex: my_db) - the id of the running container. Get it with docker ps (ex: 91ec754c8351)
<command> - the command to run inside the container (ex: bash, cat)
-w <path-to/directory> - execute a command in the specified directory (ex: /var/www/html)

$ docker exec -it <container-id> <command>

# if we give the container a name (ex: --name=my_db) we can replace <container-id> with the <host-name> (ex: my_db)
$ docker exec -it <host-name> <command>

# execute a command in a directory inside the container
$ docker exec -it -w <path-to/directory> <host-name> <command>

#example: 'app' is the <host-name> and `php artisan list` is the command
$ docker exec -it -w /var/html/www app php artisan list

Show the modifications made to a container from the base image
ex: If I create a container from ubuntu:18.04 image, then I login into it and install apache, if I run the command it will show me that I installed apache

$ docker diff <container-id>

Create a new image from a container with the commit command
Example: If I installed some packages in a container (ex: apache, php, yarn etc.) and I want to save them, I commit the changes and a new image will be created. Of course, that image will show up in the images list ($ docker image ls) and from it I can spin up a new container, identical to the initial one.
-a "<author-name>" - the author of the commit (ex: "John doe")
-m "<message-body>" - a commit message (ex: "Installed apache")
<container-id> - the id of the container to commit (ex: as5335fsa639ggf)
<new-image-name>:<tag-name> - the name of the new image that will be created (ex: myapache, myapache:latest, myapache:1.0). Note: latest and 1.0 are called image tags. If no tag is specified latest will be added by default.

$ docker commit -a "<author-name>" -m "<message-body>" <container-id> <new-image-name>:<tag-name>

Create a new image from a Dockerfile with the build command
Is similar to how we commit changes to a container to make a new image (see above)
-t <new-image-name>:<tag-name> - name and tag of the new image (ex: myapp, myapp:latest, myapp/nginx:latest). Note myapp/nginx represents the app name (namespaced name) and them the image name
-f <path-to-dockerfile> - name of the Dockerfile (Default is 'PATH/Dockerfile') (ex: docker/nginx/Dockerfile)
<dockerfile-context> - the context in which the Dockerfile to run (from where does Dockerfile gets it's resources described in his content) (ex: docker/nginx)

$ docker build -t <new-image-name>:<tag-name>
    -f <path-to-dockerfile>
    <dockerfile-context>

Read Docker logs output
-f(follow) - pass this flag to see the log output in real-time (when new output gets sent to the logs)
<container-id> - the id of the container from which to output the logs (get it by running docker ps command)\

How it works?
If a process (nginx, supervisor, php etc.) running inside a container outputs to /dev/stdout or /dev/stderr, that output is sent to the Docker logging mechanism. So, the command will output the content of the Docker logging mechanism populated with the logs from /dev/stdout and /dev/stderr.
Note: We need to configure each process (nginx, supervisor, php etc.) to output to /dev/stdout and /dev/stderr.

# basic usage
$ docker logs <container-id>

# see the container logs output in real-time by passing the "-f" (follow) flag
$ docker logs -f <container-id>

# Docker `network` - video

For two, or more, containers to communicate with each other, they need to be part of the same network. For example the app container which has php and nginx with the mysql container with the DB.

List all networks
Note: By default Docker has 3 networks defined (bridge, host and none)

$ docker network ls

Create a network @docs
<name> - the network name (ex: appnet)\

Note: the default network type will be bridge. See @docs for more details

$ docker network create <name>

Inspect a network @docs
<name> - the network name (ex: appnet)

$ docker network inspect <name>

Remove a network
<name> - the network name (ex: appnet)

$ docker network rm <name>

# Docker `volume` - video

List all volumes

$ docker volume ls

Create a new volume
<name> - the volume name (ex: mydata)

$ docker volume create <name>

Remove a volume
<name> - the volume name (ex: mydata)

$ docker volume rm <name>

# remove all volumes
$ docker volume rm $(docker volume ls -q)

How to avoid losing data, with Docker volume, after a container has been destroyed\

If we create and run a container off an image (ex: a myslq 5.7 container) and then we destroy the container, we will lost all the data saved in the mysql databases.

To avoid this, we can save the container data (state) in a volume (ex: mydata), so, when we recreate the container later on and bind it to our volume (ex: mydata), all the information will be there, not lost anymore.

Note: /var/lib/mysql - is the folder where mysql stores the data

# create 'mydata' volume
$ docker volume create mydata
# bind 'mydata' volume to the container data directory ('/var/lib/mysql' in our case)
$ docker run .... -v mydata:/var/lib/mysql ...

# Docker `Dockerfile`

CMD - Run a command inside the container after it has been started (on docker run ...)

Why would we add it to Dockerfile? An option would have been to pass the <command> to run directly to docker run ... <command>, but by adding it in the Dockerfile it is not needed anymore and it will be runned automaticly.

Note: The command can be overwritten by passing to the command docker run ... <another-command> another command <another-command>. In this case, our command from insede the Dockerfile will NOT be runned anymore!

CMD ["<command>"]

# Example - this will run "supervisord"
CMD ["supervisord"]

ENTRYPOINT - Run a command or multiple commands inside a container using a bash/shell script - video

Note: The ENTRYPOINT will be used every time when we run a container, is not like a CMD which can be overwritten (see CMD details above)

How to example:

Define a bash/shell script start-container.sh on our localhost
In Dockerfile add a new line to ADD/COPY start-container.sh inside the container from out localhost (ex: ADD start-container.sh /usr/bin/start-container)
In Dockerfile add a RUN command to set permissions for read/write the file in the container (ex: RUN chmod +x /usr/bin/start-container)
Final step, add ENTRYPOINT ["<path-to/bash-script-inside-the-container>"] to Dockerfile

<path-to/bash-script-inside-the-container> - the path (FROM INSIDE the container) to the script with all the commands to run inside that container

ENTRYPOINT ["<path-to/bash-script-inside-the-container>"]

# Example: "start-container" is the name of the file inside the container NOT in our localhost
ENTRYPOINT ["start-container"]

############ Example of "start-container" script

## Note: To get 'bash' path, access the container (docker exec <container-id>) and run the command `which bash`
#!/usr/bin/env bash
##
# Ensure /.composer exists and is writable
#
if [ ! -d /.composer ]; then
    mkdir /.composer
fi

chmod -R ugo+rw /.composer

##
# Run a command or start supervisord
#
if [ $# -gt 0 ];then
    # If we passed a command, run it
    exec "$@"
else
    # Otherwise start supervisord
    /usr/bin/supervisord
fi

`Dockerfile` example - best practices

FROM <image-name> - creates a layer from the Docker image (ex: ubuntu:18.04)\
LABEL <key>="<value>" - add labels to your image to help organize images by project, record licensing information, to aid in automation, or for other reasons\
ENV <VAR_NAME>=<value> - environment variables specific to services you wish to containerize (ex: ADMIN_USER="john", APP_VERSION=9.3.4, DEBIAN_FRONTEND=noninteractive - this var will be used inside Ubuntu config on install...is like setting a global var)\
RUN <command(s)> - executes command(s) in a new layer and creates a new image. It is often used for installing software packages. (ex: RUN apt-get update && apt-get install -y)\
ADD <path-to/local-file> <path-to/container-file> - add a file from local directory to container provided path\
COPY <path-to/local-file> <path-to/container-file> - the same as ADD. Copy the file from local directory to the container. Note: COPY is preferred over ADD (see best practices)\
CMD [<command>, <parameter(s)>] - sets default command and/or parameters, which can be overwritten from command line when docker container runs (ex: CMD ["php", "-a"]). Note: <parameter(s)> is optional (ex: CMD ["supervisord"] - start supervisord by default after the container starts running)

FROM ubuntu:18.04

LABEL maintainer="Chris Fidao"

ENV DEBIAN_FRONTEND=noninteractive
ENV ADMIN_USER="john"

RUN apt-get update \
    && apt-get install -y gnupg tzdata \
    ...

RUN apt-get update \
    && apt-get install -y curl zip unzip git supervisor sqlite3 \
       nginx php7.2-fpm php7.2-cli \
       ...
    && php -r "readfile('http://getcomposer.org/installer');" | php -- --install-dir=/usr/bin/ --filename=composer \
    && mkdir /run/php \
   ...
   
RUN echo $ADMIN_USER > ./john

ADD default /etc/nginx/sites-available/default
COPY supervisord.conf /etc/supervisor/conf.d/supervisord.conf

CMD ["supervisord"]

# `docker-compose` - videos

Require a variable inside a docker-compose.yml file like this: ${<VAR_NAME>} (ex: ${APP_NAME}).
The variable can be set globally:

with the command export <VAR_NAME>=value and the run any docker-compose command
OR it can be set in an .env file, located at the same level as docker-compose.yml

List all (only) the containers created from docker-compose.yml

$ docker-compose ps -a

List all (only) the active containers created from docker-compose.yml

$ docker-compose ps

Start all containers
<args...> (optional) - pass optional argumets (ex: --help, -d etc.)\

Note: As an workflow, is recommanded to use up and down commands, NOT start and stop

$ docker-compose up <args...>

Stop and destroy all running containers
Note: As an workflow, is recommanded to use up and down commands, NOT start and stop

$ docker-compose down

Restart all containers
Note: It will reset and regrab the new settings from docker-compose.yml. In case I did changes to the composer file it will apply them.

$ docker-compose restart

Executea a command inside a container
Note: If we didn't set a working directory (working_dir) in docker-compose.yml file for our application container, we will need to specify it in the command like this: -w <path-to/working-directory> (ex: -w /var/www/html)
<container-name> - name of the container. Get it with command docker-compose ps
<command> - the command you want to run inside the container (ex: bash, php artisan migrate, composer require ...)

$ docker-compose exec <container-name> <command>
# example including setting the working directory
$ docker-compose exec -w /var/www/html app composer require predis/predis

`docker-compose.yml` example

version: '3'
services:
  app:
    # If the image doesn't exsit on Docker Hub we need to add a 'build' parameter. 'build' + 'image' is the same as 'docker build -t shippingdocker/app:latest -f docker/app/Dockerfile docker/app'
    build:
      context: ./docker/app
      dockerfile: Dockerfile
    image: shippingdocker/app:latest
    networks:
      - appnet
    volumes:
      # "." is the path to the laravel application. In our case docker-compose.yml is in the same directory with the laravel application 
      - .:/var/www/html
    ports:
      - ${APP_PORT}:80
    working_dir: /var/www/html
  cache:
    image: redis:alpine
    networks:
      - appnet
    volumes:
      # see docs - https://hub.docker.com/_/redis and here https://github.com/docker-library/redis/blob/7ccc22760cc9b659916678a52654be8f43757551/6.0/alpine/Dockerfile
      - cachedata:/data
    ports:
      - 6379:6379
  db:
    image: mysql:5.7
    environment:
      MYSQL_ROOT_PASSWORD: secret
      MYSQL_DATABASE: homestead
      MYSQL_USER: homestead
      MYSQL_PASSWORD: secret
    networks:
      - appnet
    volumes:
      # more details in the docs - https://hub.docker.com/_/mysql
      - dbdata:/var/lib/mysql
    ports:
      - ${DB_PORT}:3306
  node:
    build:
      context: ./docker/node
      dockerfile: Dockerfile
    image: shippingdocker/node:latest
    networks:
      - appnet
    volumes:
      # "." is the path to the laravel application. In our case docker-compose.yml is in the same directory with the laravel application 
      - .:/opt
    working_dir: /opt
    command: echo hi
networks:
  appnet:
    driver: bridge
volumes:
  dbdata:
    driver: local
  cachedata:
    driver: local

# Linux commands geeksforgeeks.org

pwd(print working directory) - Print path of the current working directory

$ pwd
# Use it in docker commands like a dynamic variable, to share for example a directory into a docker container
$ docker run -d -p 8080:80 -v $(pwd)/myapplication:/var/www/html/public myimage:latest ...

which - Locate the executable file associated with the given command by searching it in the path environment variable
<name> - can be one or multiple names

$ which <name>
# example 
$ which nginx, php, redis

ps(Process Status) - show the processes running under the logged in user account from the current terminal
a - prints the running processes from all users
u - shows user or owner column in output
x - prints the processes those have not been executed from the terminal
aux (all the above options together) - print all the running processes in the system regardless from where they have been executed

$ ps aux

getent - get entries from administrative database (ex: hosts, passwd, group, service, protocols etc.) - @docs

$ getent <administrative-database> <name>

# example 1: get the IPs a hostname (mysql) points to.
$ getent hosts mysql

# example 2: without parameters, this will show you all the groups found on the server
$ getent group

# Mysql commands

How to create MySQL users accounts and grant privileges - @see docs

How to show a list of all databases - @see docs

How to show tables in a database - @see docs

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README.md

README.md

Running example and Docker commands extracted from Server for hackers free series on containers.

# Docker commands

# Docker `network` - video

# Docker `volume` - video

# Docker `Dockerfile`

`Dockerfile` example - best practices

# `docker-compose` - videos

`docker-compose.yml` example

# Linux commands geeksforgeeks.org

# Mysql commands

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Running example and Docker commands extracted from Server for hackers free series on containers.

# Docker commands

# Docker network - video

# Docker volume - video

# Docker Dockerfile

Dockerfile example - best practices

# docker-compose - videos

docker-compose.yml example

# Linux commands geeksforgeeks.org

# Mysql commands

# Docker `network` - video

# Docker `volume` - video

# Docker `Dockerfile`

`Dockerfile` example - best practices

# `docker-compose` - videos

`docker-compose.yml` example