Multiple Dockerfiles - docker

Question

I am trying to use docker and want to create an Ubuntu base with three containers that do the following:
Container: Install Wildfly
Container: Install MySQL
Container: Other Required Packages
Does that mean, I have to create three Dockerfiles in three different directories containing each the following top line?:
FROM ubuntu:18.04

Answer 1

Orchestrate the containers with docker-compose
1- Create docker-compose.yml
2- Inside define:
version: '3'
services:
wildly:
build:
context: .
dockerfile: Dockerfile_Wildfly
mysql:
build:
context: .
dockerfile: Dockerfile_Mysql
anotherpackages:
build:
context: .
dockerfile: Dockerfile_AnotherPackages
it is not always the case that you need to write a docker file, for example for the database service you can simply pull the image from the docker hub and use it directly.
something like below
db:
image: mysql
3- Create files and both define commands you prefer:
Dockerfile_Wildfly
FROM wildfly
Dockerfile_Mysql
FROM mariadb
Dockerfile_AnotherPackages
FROM node
FROM nginx

Answer 2

You can create many Dockerfile and precise their name in the build command as suggested in another answer (#Krumelur's answer), but you can also use docker compose by calling directly the image from docker.io (if the base image for those dependecies in the hub match your neeed)
In this way you dont need any Dockerfile at all.
It should looks like this :
version: '3.3'
services:
wildfly:
#this image will be automatically downloaded from your registry (by default Docker hub)
image: jboss/wildfly
ports:
- '8080:8080'
- '9990:9990'
volumes:
- 'wildfly_data:/wildfly_data'
environment:
- WILDFLY_PASSWORD=password
mysql:
#this image will be automatically downloaded from your registry (by default Docker hub)
image: mysql:5.7
restart: always
environment:
MYSQL_DATABASE: 'db'
# So you don't have to use root, but you can if you like
MYSQL_USER: 'user'
# You can use whatever password you like
MYSQL_PASSWORD: 'password'
# Password for root access
MYSQL_ROOT_PASSWORD: 'password'
ports:
# <Port exposed> : < MySQL Port running inside container>
- '3306:3306'
expose:
# Opens port 3306 on the container
- '3306'
# Where our data will be persisted
volumes:
- my-db:/var/lib/mysql
otherService :
image: busybox
volumes:
my-db:
wildfly_data:
Then you just need to call the command : docker-compose up

Answer 3

You can have more than one Dockerfile in the same directory if desired. To specify the Dockerfile to use, use the -f argument, e.g
docker build -f wildfly.Dockerfile ./wildfly
docker build -f mysql.Dockerfile ./mysql
docker build -f other.Dockerfile ./other
In Compose, these arguments correspond to the dockerfile and context properties.
It is not always the case that you need to write a docker file, for example for the database service you can simply pull the image from the docker hub and use it directly.
something like below
db:
image: mysql
You can, of course, have them share the same context, e.g.
docker build -f wildfly.Dockerfile .
docker build -f mysql.Dockerfile .
docker build -f other.Dockerfile .
Just be aware that the context is sent in full to the daemon (respecting .dockerignore) so this might lead to longer build times if there is a lot of redundant data.
If there is a lot of reuse between the Dockerfiles, you can even have all of them in one file, e.g.
FROM ubuntu:20.04 as base
...
FROM base AS wildfly
(install wildfly)
FROM base AS mysql
(install mysql)
...
Then you can build the specific image with e.g.
docker build --target wildfly .
In Compose, these arguments correspond to the target and context properties.
This is called multi-stage builds, and is not always a good idea but is sometimes helpful to mitigate Docker's lack of support for #include.