How Containers work?
- Refer Here for the docker internals.
Trails
- Every docker container has a command that gets executed when the container is created/started. As long as that command is running the container will be in running state, if that command has finished execution container will be stopped or exited
Lets create a docker container and install our application in it
- to run the container in the background mode (detached mode) we use -d
- The application which i want to run is apache server
sudo apt update
sudo apt install apache2 -y
- Apache runs on port 80
- Create a docker contianer with ubuntu image. Run it in the interactive mode.
- Ensure port forwarding is set
docker container run -p 8081:80 -it ubuntu:22.04 /bin/bash
# apt update
# apt install apache2 -y
# service apache2 start
-
Now access the
http://<ip of docker host>:8081
- This might run the application but is not a good way as i need to do installation for every container created.
Lets create a docker image by manually installing softwares in container
- Lets install a nginx in some container and create a image out of it
- lets create a container in a interactive mode
docker container run -p 8082:80 -it ubuntu:22.04 /bin/bash
# apt update
# apt install nginx -y
# service nginx start
- Now lets create a docker image from running container
- In the docker host
docker commit <container-name/id>
* Now lets create an image and tag based the image id
* This approach creates images but no history of changes are available.
Dockerfile approach
- Dockerfile approach is all about using instrcutions to inform docker what needs to be done when creating the image, starting the contianer. What are the metadata about your image
- Dockerfile has instructions to containerize the application.
- Dockerfile can be written in any text file, but file a name
Dockerfileis most commonly used - Lets take a very simple Dockerfile
FROM alpine:latest
CMD ["echo", "Welcome to container world"]
- Now lets try to build
- Create a new folder and create a file with name
Dockerfilewith the above content
- Now check images
- Lets run the container from the image
