Containerization

By definition : is the method by which packaging software and their dependencies are turned into lightweight, portable unit called containers.

Unlike virtual machines, containers share the host operating system, making them more efficient in terms of resources.

In isolating software applications and their dependencies, containers are a great way to simplify development, deployment, and scaling of features. We commonly see Docker and Kubernetes as sources for managing containers and viewing their application details.

Docker

In Linux we commonly use Docker, and to do so we want to first allow access to it in the terminal.

# sudo dnf config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.rep

As well as install Docker and the needed dependencies.

# sudo dnf install -y docker-ce docker-ce-cli containerd.io docker-compose-plug

The following code proceeds the previous steps:

# sudo systemctl start docker

# sudo systemctl enable docker

and final step to using docker for containerization is to allow non-root access:

# sudo usermod -aG docker $USER

To verify that the correct steps were followed use the following:

docker --version

docker run hello-world

Now that we have verified docker is working, here is a list of code we use and what they do.

docker pull {image_name} -> image can be found on docker.io

docker run {image} -> allows the image to be implimented

docker ps -> verifys which containers are actively running
docker ps -a -> views all containers

docker stop {container ID or name} -> stops the container from running

docker rm {container ID or name} -> removes/deletes the container

docker images -> shows the pulled containers

Docker Storage

We can also add storage to containers which gives a variety of benefits; for example an archive of file logs.

There are three varieties: 1. Temporary storage - resides inside of conatiners, only remains while container is active. While stopped the files are retained, but when deleted so are the files.

2. Volumes - storage that is self-contained and can be connected to a container. Easy to backup or share between containers.

3. Bind mounts - storage that is a folder on your system that you want to be accessible from the container. Can be done by mapping a folder to a folder inside a container.

Docker code for storage purposes:

# docker run -it --name {name or storage} 

# docker start -it --name -> -it allows an interactive terminal.

# docker start -i {name} -> starts container again

# docker volume create {name}

# docker exec -it {container name or ID} bash

# docker stop volume

# docker rm volume

# docker volume ls

networking

Allows containers to communicate with each other.

# docker network ls

# docker network create {name}

# docker run -id --network {name} --name {conatiner name} {operating system}

# docker network inspect {network name}

# docker network connect {network name} {container name or ID}

# docker network disconnect bridge {container name or ID}

# docker network rm {network name}