The below docker commands should give you a basic understanding of how docker works. This is obviously not a comprehensive lesson, but should give you enough information to take off on your own.
Create an account
Login to docker hub
docker login
Search docker hub
docker search centos
Run a basic container
Run in detached mode on internal port 80, external port 5001 using the httpd:2.4 image on docker hub, and name the container itsmetommy-httpd.
docker run -d --name itsmetommy-httpd -p 5001:80 httpd:2.4
- -name <container_name>
- -d detached mode
- -p <external_port>:<internal_port>
- <image_name>:<version> (e.g. httpd:2.4)
View your URL
View your images
docker images | grep httpd
View running docker containers
docker ps
View running and stopped docker containers
docker ps -a
Run centos in interactive and tty mode
docker run -it --name itsmetommy-centos centos
Exit the container.
exit
- -it instructs Docker to allocate a pseudo-TTY connected to the container’s stdin; creating an interactive bash shell in the container
- exit out of the container
View your running docker containers
docker ps
View your running and stopped docker containers
Notice that itsmetommy-centos is stopped. This is due to you not running in detached mode.
docker ps -a
Start itsmetommy/centos back up
docker start itsmetommy-centos
View your running docker containers
Notice that itsmetommy/centos is now running.
docker ps
Lets connect to itsmetommy/centos
docker attach itsmetommy-centos
If you type ‘exit’ you will by design stop the container.
This is where pressing CTRL P + Q comes in handy.
CTRL P + Q
You can see that itsmetommy-centos is still running.
docker ps
Stop the docker containers
docker stop itsmetommy-httpd;docker stop itsmetommy-centos
View your running and stopped docker containers
docker ps -a
Remove the docker containers
docker rm itsmetommy-httpd;docker rm itsmetommy-centos
Create a project directory
mkdir learn-docker;cd learn-docker
Create a public-html directory with index.html
mkdir public-html;echo "Hello World" > public-html/index.html
Create a Dockerfile
What if we want to record our changes and build our own image? Dockerfiles to the rescue!
This will download the httpd image from docker hub and copy the contents from public-html into /usr/local/apache2/htdocs within the httpd container.
vi Dockerfile
FROM httpd:2.4
COPY ./public-html/ /usr/local/apache2/htdocs/
EXPOSE 80
Build
This will build a new image called itsmetommy/learn-docker based on the Dockerfile.
docker build -t itsmetommy/learn-docker .
- -t tag
Push
Important: Create a repository on docker hub. My repository is named itsmetommy.
Now push your new image to your docker hub repository.
Important: Substitute itsmetommy with your repository name.
docker push itsmetommy/learn-docker
https://hub.docker.com/u/itsmetommy/
Volumes
Volumes give a running container the ability to see files on the host machines file system. They DO NOT change the image.
If you ever wanted to make any changes to lets say index.html, it would be a pain to have to re-build the image every time you test a change. This is where mounting your local volume within the container comes into play.
Lets run the container again except with a volume mount.
Note: You must put the full path (not relative).
docker run -d -p 5001:80 -v /Users/$USER/learn-docker/public-html:/usr/local/apache2/htdocs/ --name itsmetommy-learn-docker itsmetommy/learn-docker
IMPORTANT: If you update any files, you will need to re-build the image to get an updated copy of the image.
Test
Now update your local index.html file.
echo "Hello $USER" > public-html/index.html
http://localhost:5001 # refresh browser
Awesome right? 🙂
Clean up: Stop/remove/delete the container
docker stop itsmetommy-learn-docker;docker rm itsmetommy-learn-docker;docker rmi itsmetommy/learn-docker
Doing a bunch of docker run commands can be a huge pain.
That’s where docker-compose saves the day.
Docker-compose: Create a learn-docker-compose folder and cd into it
mkdir learn-docker-compose; cd learn-docker-compose
Docker-compose: Create the httpd and nginx folders and files
mkdir -p httpd/public-html nginx/public-html; echo "Hello HTTPD" > httpd/public-html/index.html; echo "Hello NGINX" > nginx/public-html/index.html
Docker-compose: Create docker-compose.yml
vi docker-compose.yml
version: '3'
services:
apache2:
build: ./httpd
image: httpd
volumes:
- ./httpd/public-html:/usr/local/apache2/htdocs
ports:
- 5001:80
container_name: itsmetommy-httpd
nginx:
build: ./nginx
image: nginx
volumes:
- ./nginx/public-html:/usr/share/nginx/html
ports:
- 5002:80
container_name: itsmetommy-nginx
Docker-compose: Run docker-compose up
docker-compose up -d
- -d detached mode
Docker-compose: View your sites
http://localhost:5001
http://localhost:5002
Docker-compose: Update index.html and refresh browsers
Update the httpd and nginx index.html file.
echo "Hello HTTPD 2.0" > httpd/public-html/index.html echo "Hello NGINX 2.0" > nginx/public-html/index.html
http://localhost:5001 # refresh
http://localhost:5002 # refresh
Docker-compose: List containers
docker-compose ps
Docker-compose: Run docker-compose stop
This stops the containers.
docker-compose stop
Docker-compose: Run docker-compose kill
If the containers won’t stop, you can issue a kill.
docker-compose kill
Docker-compose: Finally, remove the containers
docker-compose rm
