What s the difference between Docker Compose vs Dockerfile

Question

I have been reading up and learning about Docker  and am trying to correctly choose the Django setup to use  So far there is either   Docker Compose or Dockerfile  I understand that Dockerfiles are used in Docker Compose  but I am not sure if it is good practice to put everything in one large Dockerfile with multiple FROM commands for the different images   I want to use several different images that include   uwsgi nginx postgres redis rabbitmq celery with cron   Please advise on what are best practices in setting up this type of environment using Docker   If it helps  I am on a Mac  so using boot2docker   Some Issues I ve had    Docker Compose is not compatible with Python3 I want to containerize my project  so if one large Dockerfile  is not ideal  then I feel I d need to break it up using Docker Compose I am ok to make the project Py2  amp  Py3 compatible  so am leaning towards django-compose

User · Answer

In Microservices world  having a common shared codebase   each Microservice would have a Dockerfile whereas at the root level  generally outside of all Microservices and where your parent POM resides   you would define a docker-compose yml to group all Microservices into a full-blown app   In your case  Docker Compose  is preferred over  Dockerfile    Think  App  Think  Compose

User · Answer

In my workflow  I add a Dockerfile for each part of my system and configure it that each part could run individually  Then I add a docker-compose yml to bring them together and link them   Biggest advantage  in my opinion   when linking the containers  you can define a name and ping your containers with this name  Therefore your database might be accessible with the name db and no longer by its IP

User · Answer

Dockerfile and Docker Compose are two different concepts in Dockerland  When we talk about Docker  the first things that come to mind are orchestration  OS level virtualization  images   containers  etc   I will try to explain each as follows   Image  An image is an immutable  shareable file that is stored in a Docker-trusted registry  A Docker image is built up from a series of read-only layers  Each layer represents an instruction that is being given in the image   s Dockerfile  An image holds all the required binaries to run     Container  An instance of an image is called a container  A container is just an executable image binary that is to be run by the host OS  A running image is a container     Dockerfile  A Dockerfile is a text document that contains all of the commands   build instructions  a user could call on the command line to assemble an image  This will be saved as a Dockerfile   Note the lowercase  f       Docker-Compose  Compose is a tool for defining and running multi-container Docker applications  With Compose  you use a YAML file to configure your application   s services  containers   Then  with a single command  you create and start all the services from your configuration   The Compose file would be saved as docker-compose yml

User · Answer

Imagine you are the manager of a software company and you just bought a brand new server  Just the hardware   Think of Dockerfile as a set of instructions you would tell your system adminstrator what to install on this brand new server  For example    We need a Debian linux add an apache web server we need postgresql as well install midnight commander when all done  copy all   php    jpg  etc  files of our project into the webroot of the webserver   var www    By contrast  think of docker-compose yml as a set of instructions you would tell your system administrator how the server can interact with the rest of the world  For example     it has access to a shared folder from another computer   it s port 80 is the same as the port 8000 of the host computer   and so on     This is not a precise explanation but good enough to start with

User · Answer

The answer is neither    Docker Compose  herein referred to as compose  will use the Dockerfile if you add the build command to your project s docker-compose yml    Your Docker workflow should be to build a suitable Dockerfile for each image you wish to create  then use compose to assemble the images using the build command    You can specify the path to your individual Dockerfiles using build  path to dockerfiles blah where  path to dockerfiles blah is where blah s Dockerfile lives

User · Answer

Dockerfile is a file that contains text commands to assemble an image   Docker compose is used to run a multi-container environment   In your specific scenario  if you have multiple services for each technology you mentioned  service 1 using reddis  service 2 using rabbit mq etc   then you can have a Dockerfile for each of the services and a common docker-compose yml to run all the  Dockerfile  as containers   If you want them all in a single service  docker-compose will be a viable option

User · Answer

The Compose file describes the   container in its running state  leaving the details on how to build   the container to Dockerfiles    http   deninet com blog 1587 docker-scratch-part-4-compose-and-volumes      When you define your app with Compose in development  you can use this   definition to run your application in different environments such as   CI  staging  and production    https   docs docker com compose production    It is also seems that Compose is considered production safe as of 1 11  since https   docs docker com v1 11 compose production  no longer has a warning not to use it in production like https   docs docker com v1 10 compose production  does

User · Answer

docker-compose exists to keep you having to write a ton of commands you would have to with docker-cli  docker-compose also makes it easy to startup multiple containers at the same time and automatically connect them together with some form of networking  The purpose of docker-compose is to function as docker cli but to issue multiple commands much more quickly  To make use of docker-compose  you need to encode the commands you were running before into a docker-compose yml file  You are not just going to copy paste them into the yaml file  there is a special syntax  Once created  you have to feed it to the docker-compose cli and it will be up to the cli to parse the file and create all the different containers with the correct configuration we specify  So you will have separate containers  let s say  one is redis-server and the second one is node-app  and you want that created using the Dockerfile in your current directory  Additionally  after making that container  you would map some port from the container to the local machine to access everything running inside of it  So for your docker-compose yml file  you would want to start the first line like so  version   3   That tells Docker the version of docker-compose you want to use  After that  you have to add  version   3  services     redis-server       image   redis    node-app      build     Please notice the indentation  very important  Also  notice for one service I am grabbing an image  but for another service I am telling docker-compose to look inside the current directory to build the image that will be used for the second container  Then you want to specify all the different ports that you want open on this container  version   3  services     redis-server       image   redis    node-app      build        ports        -  Please notice the dash  a dash in a yaml file is how we specify an array  In this example  I am mapping 8081 on my local machine to 8081 on the container like so  version   3  services     redis-server       image   redis    node-app      build        ports        -  quot 8081 8081 quot   So the first port is your local machine  and the other is the port on the container  you could also distinguish between the two to avoid confusion like so  version   3  services    redis-server      image   redis    node-app      build        ports        -  quot 4001 8081 quot   By developing your docker-compose yml file like this  it will create these containers on essentially the same network and they will have free access to communicate with each other any way they please and exchange as much information as they want  When the two containers are created using docker-compose  we do not need any port declarations  Now in my example  we need to do some code configuration in the Nodejs app that looks something like this  const express   require  express    const redis   require  redis     const app   express    const client   redis createClient     host   redis-server       I use this example above to make you aware that there may be some specific configuration you would have to do in addition to the docker-compose yml file that may be specific to your project  Now  if you ever find yourself working with a Nodejs app and redis  you want to ensure you are aware of the default port Nodejs uses  so I will add this  const express   require  express    const redis   require  redis     const app   express    const client   redis createClient     host   redis-server     port  6379      So Docker is going to see that the Node app is looking for redis-server and redirect that connection over to this running container  The whole time  the Dockerfile only contains this  FROM node alpine  WORKDIR   app   COPY  package json    RUN npm install COPY      CMD   quot npm quot    quot start quot    So  whereas before you would have to run docker run myimage to create an instance of all the containers or services inside the file  you can instead run docker-compose up and you don t have to specify an image because Docker will look in the current working directory and look for a docker-compose yml file inside  Before docker-compose yml  we had to deal with two separate commands of docker build   and docker run myimage  but in the docker-compose world  if you want to rebuild your images  you write docker-compose up --build  That tells Docker to start up the containers again but rebuild it to get the latest changes  So docker-compose makes it easier for working with multiple containers  The next time you need to start this group of containers in the background  you can do docker-compose up -d  and to stop them  you can do docker-compose down

User · Answer

Dockerfiles are to build an image for example from a bare bone Ubuntu  you can add mysql called mySQL on one image and mywordpress on a second image called mywordpress  Compose YAML files are to take these images and run them cohesively  For example  if you have in your docker-compose yml file a service called db  services     db       image  mySQL  --- image that you built   and a service called wordpress such as  wordpress       image  mywordpress  then inside the mywordpress container you can use db to connect to your mySQL container   This magic is possible because your docker host create a network bridge  network overlay

User · Answer

Dockerfile  A Dockerfile is a simple text file that contains the commands a user could call to assemble an image  Example   Dockerfile FROM ubuntu latest MAINTAINER john doe   RUN apt-get update RUN apt-get install -y python python-pip wget RUN pip install Flask  ADD hello py  home hello py  WORKDIR  home   Docker Compose  Docker Compose  is a tool for defining and running multi-container Docker applications   define the services that make up your app in docker-compose yml so they can be run together in an isolated environment   get an app running in one command by just running  docker-compose up   Example  docker-compose yml version   quot 3 quot  services    web      build        ports      -  5000 5000      volumes      -    code     - logvolume01  var log     links      - redis   redis      image  redis     volumes        logvolume01

User · Answer

quot better quot  is relative  It all depends on what your needs are  Docker compose is for orchestrating multiple containers  If these images already exist in the docker registry  then it s better to list them in the compose file  If these images or some other images have to be built from files on your computer  then you can describe the processes of building those images in a Dockerfile   I understand that Dockerfiles are used in Docker Compose  but I am not sure if it is good practice to put everything in one large Dockerfile with multiple FROM commands for the different images   Using multiple FROM in a single dockerfile is not a very good idea because there is a proposal to remove the feature  13026 If for instance  you want to dockerize an application which uses a database and have the application files on your computer  you can use a compose file together with a dockerfile as follows docker-compose yml mysql    image  mysql 5 7   volumes      -   db-data  var lib mysql   environment      -  quot MYSQL ROOT PASSWORD secret quot      -  quot MYSQL DATABASE homestead quot      -  quot MYSQL USER homestead quot    ports      -  quot 3307 3306 quot  app    build      context    path to Dockerfile     dockerfile  Dockerfile   volumes      -     app   working dir   app         Dockerfile FROM php 7 1-fpm  RUN apt-get update  amp  amp  apt-get install -y libmcrypt-dev     mysql-client libmagickwand-dev --no-install-recommends      amp  amp  pecl install imagick      amp  amp  docker-php-ext-enable imagick      amp  amp  docker-php-ext-install pdo mysql      amp  amp  curl -sS https   getcomposer org installer   php -- --install-dir  usr local bin --filename composer

[docker] What's the difference between Docker Compose vs. Dockerfile

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