The services section in a docker-compose file is an array of containers which are to be built and run together when the docker-compose file is executed. Each container under a docker-compose file is indicated with a user specific "service_name" which is used by other containers for communication among themselves. These "service names" need to be unique within a docker-compose file and are auto resolved for their respective containers by the docker.

version: '3'
services: 
    redis-server:
        build: .
        ports:
            - 8000:6379
     angular-app:
        build: .
        ports:
            - 8080:80

A Dockerfile is a set of instructions about how a container for an application shall be built from the scratch using a base image. A docker-compose is a yaml script which comprises of how multiple docker containers grouped under a single subnet shall be built and run.

A docker-compose file runs on top of a Dockerfile and requires a path for the Dockerfile to be specified in the script for custom containers.

A docker-compose is a command which comes out of the box along with the docker installation, that helps in keeping instructions to run a container out of an image simple without missing out on any instruction which needs to be passed on while creating a container. A Docker-compose file is a yaml script, which contains an elaborated set of instructions about how to build and run a docker container.

A Dockerfile can be built and run in the same way a normal container is created and run.

> docker build -t <docker_hub_user_id>/<repository_name>[:version_tag] <path_to_dockerfile>

Where -t refers to an image_tag: a unique readable name assigned to the created image by the developer for future references.

Example:

> docker build -t refebruvuser/mynpm .

And is run as:

> docker run -i -t <docker_hub_user_id>/<repository_name>[:version_tag]

A Dockerfile is a file of same name with no extension. It typically contains three parts or steps in which a container shall be built.

1. Specify a base Image
2. Instructions on how to build and deploy the application onto the base Image
3. A Startup command to specify how the container should behave once started

A Dockerfile is a configuration file which contains instructions for docker on how to build a customized image from an existing base image and how to get things started. It can be treated as a build script for a docker container.

docker PS command gives user the ability to monitor all the created containers in the system.

> docker ps

Command shows all the containers which are currently running in the system. Adding an -a flag to the command shows all the containers which are available in the system (both running and stopped).

The "it" flag is used in a RUN or EXEC command, which is a combination of two individual flags i and t.

i stands for interactive, which connects the user terminal to the STDIN of the container. The t flag refers to pseudo-tty which pretty prints the STDOUT channel of the container.

Example:

> docker run -it ubuntu bash

The above command runs an ubuntu container and connects the bash command output to the user terminal, which results in the ability for user to send and receive I/O onto the container.