Docker file and compose update

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I have created a simple tech stack using Docker. PHP 7.2 on CentOS.

Below is the docker file

FROM centos:7

# Install Apache
RUN yum -y update
RUN yum -y install httpd httpd-tools

# Install EPEL Repo
RUN rpm -Uvh https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm \
 && rpm -Uvh https://mirror.webtatic.com/yum/el7/webtatic-release.rpm

# Install PHP
RUN yum -y install php72w php72w-bcmath php72w-cli php72w-common php72w-gd php72w-intl php72w-ldap php72w-mbstring \
    php72w-mysql php72w-pear php72w-soap php72w-xml php72w-xmlrpc

# Update Apache Configuration
RUN sed -E -i -e '/<Directory "\/var\/www\/html">/,/<\/Directory>/s/AllowOverride None/AllowOverride All/' /etc/httpd/conf/httpd.conf
RUN sed -E -i -e 's/DirectoryIndex (.*)$/DirectoryIndex index.php \1/g' /etc/httpd/conf/httpd.conf

EXPOSE 80

# Start Apache
CMD ["/usr/sbin/httpd","-D","FOREGROUND"]

Below is the docker-compose.yml

version: '3.2'
  services:
   centos-php-apache:
     build:
       context: ./
     ports:
      - "8080:80"
     volumes:
      - ./code:/var/www/html

All is now running fine. After few days, I decided to update the following -

(i) Update “dockerfile” by adding another php-module or php-extension

(ii) Update the docker compose.yml by adding another service (say) “mariadb”.

I would like to do this update, without effecting or deleting any files from the previous setup. In fact, this is a common scenario, where developers may need additional extensions or service in the future - without redoing everything right from the beginning.

Should I directly edit the "dockerfile" and add the php extension and edit the docker-compose.yml file and add the service as usual and then run the docker-compose up command. Of course before running the "up" command, I will first bring it down using the docker-compose down command.

Can anyone throw some light, on how I can accomplish this.

dockerfile docker-compose docker
2 Answers

It would be best if you used docker-compose up --build centos-php-apache instead of docker-compose up . And you do not want to worry about data. They are persistent with your volume map. Also, make sure to use another volume map for your mariadb data.

user_70379490

I am adding a dummy setup, together with the contents of the files:

tree
.
├── docker-compose.yml
├── mariadb
│   └── Dockerfile
└── web-app
    └── Dockerfile

------------------------

cat docker-compose.yml
version: "3"
services:
  webapp:
    build:
      context: ./web-app
      dockerfile: Dockerfile
  mariadb:
    build:
      context: ./mariadb
      dockerfile: Dockerfile
    environment:
      - MYSQL_ROOT_PASSWORD=supersecret

------------

cat mariadb/Dockerfile 
FROM mariadb
RUN echo "hello from mariadb"

------------

cat web-app/Dockerfile 
FROM nginx
RUN echo "Hello"
RUN echo "from web-app"
# ^^ that's an example for a change that you want to perform(adding a new module) ^^

Assuming that you just performed the change in the web-app/Dockerfile, you have a couple of options:

Option A:

You rebuild one specific image, while the current containers are not affected:

docker-compose build webapp

Building webapp
Step 1/3 : FROM nginx
 ---> 2622e6cca7eb
Step 2/3 : RUN echo "Hello"
 ---> Using cache
 ---> ad39a2920d75
Step 3/3 : RUN echo "from web-app"
 ---> Running in ea62a9e81110
from web-app
Removing intermediate container ea62a9e81110
 ---> 9fc79785a4c4

When you are comfortable with the image that you built, redeploy the containers that suffered image changes(note that if you run docker-compose up, only the web-app is redeployed):

docker-compose up -d  

stack-example_mariadb_1 is up-to-date
Recreating stack-example_webapp_1 ... done

Option B:

If your confident with the changes that you performed on the Dockerfile, go for the one-liner with the --build option:

docker-compose up -d --build 

Building webapp
Step 1/4 : FROM nginx
 ---> 2622e6cca7eb
Step 2/4 : RUN echo "Hello"
 ---> Using cache
 ---> ad39a2920d75
Step 3/4 : RUN echo "from web-appi"
 ---> Running in 8cbd41c34d35
from web-appi
Removing intermediate container 8cbd41c34d35
 ---> ed7bc1950d4c
Step 4/4 : RUN echo "change 2"
 ---> Running in f52be965609f
change 2
Removing intermediate container f52be965609f
 ---> da600ed3f0ed
Successfully built da600ed3f0ed
Successfully tagged stack-example_webapp:latest
Building mariadb
Step 1/2 : FROM mariadb
 ---> 8075b7694a2d
Step 2/2 : RUN echo "hello from mariadb"
 ---> Using cache
 ---> 89f75af407fe
Successfully built 89f75af407fe
Successfully tagged stack-example_mariadb:latest
Recreating stack-example_webapp_1 ... 
Recreating stack-example_webapp_1 ... done
user_137365250
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