Dockerfile Instructions And Docker Run Commands: A Comprehensive Guide

Dockerfile Instructions

FROM: Sets the base image for subsequent instructions.
```
FROM ubuntu:20.04 
```
RUN: Executes commands in a new layer on top of the current image.
```
RUN apt-get update && apt-get install -y curl 
```
MAINTAINER (Deprecated): Identifies the image creator. Use LABEL instead.
```
LABEL maintainer="[email protected]" 
```

LABEL: Adds metadata to the image.

LABEL version="1.0" description="My Docker Image"

ADD: Copies files from a source (supports URLs and tar extraction).
```
ADD https://example.com/file.tar.gz /tmp/ 
```
COPY: Copies files from host to container (no URL support).
```
COPY ./app /usr/src/app 
```
VOLUME: Creates a mount point for external storage.
```
VOLUME /data 
```
EXPOSE: Declares a container’s listening port.
```
EXPOSE 8080 
```
WORKDIR: Sets the working directory for subsequent commands.
```
WORKDIR /app 
```
USER: Specifies the user for running processes.
```
USER appuser 
```
STOPSIGNAL: Sets the system call signal for stopping the container.
```
STOPSIGNAL SIGTERM 
```
ENTRYPOINT: Configures the container’s main executable.
```
ENTRYPOINT ["python", "app.py"] 
```
CMD: Provides default arguments for the ENTRYPOINT or runs a command.
```
CMD ["--help"] 
```
ENV: Sets environment variables.
```
ENV API_KEY=12345 
```

Docker Run Commands

–name: Assigns a name to the container.
```
docker run --name my_container nginx 
```
-v, –volume: Mounts a host directory into the container.
```
docker run -v /host/path:/container/path nginx 
```
–network: Connects the container to a network.
```
docker run --network=bridge nginx 
```
-d, –detach: Runs the container in the background.
```
docker run -d nginx 
```
-i, –interactive: Keeps STDIN open for interaction.
```
docker run -i ubuntu bash 
```
-t, –tty: Allocates a pseudo-TTY.
```
docker run -it ubuntu bash 
```
–rm: Automatically removes the container after exit.
```
docker run --rm alpine echo "Hello" 
```
-e, –env: Sets environment variables.
```
docker run -e "ENV=prod" nginx 
```
–restart: Defines the container’s restart policy.
```
docker run --restart=always nginx 
```

Core Docker Concepts

Docker Image: A read-only template with instructions for creating a container.
Docker Container: A runnable instance of an image.
Docker Client: CLI tool for interacting with Docker.
Docker Daemon: Background service managing Docker objects.
Docker Registry: Hosts Docker images (e.g., Docker Hub).

You Should Know:

Essential Docker Commands

1. List Running Containers

docker ps

2. List All Containers (Including Stopped Ones)

docker ps -a

3. Build a Docker Image

docker build -t my-image:1.0 .

4. Remove a Container

docker rm container_name

5. Remove All Stopped Containers

docker container prune

6. Pull an Image from Docker Hub

docker pull nginx:latest

7. Execute a Command Inside a Running Container

docker exec -it container_name bash

8. View Logs of a Container

docker logs container_name

9. Inspect a Container’s Details

docker inspect container_name

10. Stop a Running Container

docker stop container_name

What Undercode Say

Docker is a powerful tool for containerization, enabling consistent environments across development, testing, and production. Mastering Dockerfile instructions and docker run commands is essential for DevOps engineers, cloud architects, and developers.

Additional Linux & Windows Commands for Docker Management

Linux Disk Space Cleanup (Remove Unused Docker Objects)
```
docker system prune -a 
```
Windows PowerShell Docker Cleanup
```
docker system prune --volumes 
```
Check Docker Disk Usage
```
docker system df 
```
Run a Temporary Alpine Linux Container
```
docker run --rm -it alpine sh 
```

Export a Docker Container to a Tar File

docker export container_name > backup.tar

Import a Docker Image from a Tar File

docker import backup.tar my-image:restored

Tag and Push an Image to Docker Hub

docker tag local-image:tag username/repo:tag 
docker push username/repo:tag

Run a Docker Container with Resource Limits

docker run -it --memory="1g" --cpus="1.5" ubuntu

Create a Docker Network for Multi-Container Apps
```
docker network create my-network 
```

Connect a Container to a Network

docker network connect my-network container_name

Expected Output:

A structured, detailed guide on Dockerfile instructions, Docker run commands, and essential Docker management techniques for IT professionals.

Prediction:

Docker will continue to dominate containerization, with tighter Kubernetes integration and improved security features in future releases.

References:

Reported By: Satya619 %F0%9D%90%83%F0%9D%90%A8%F0%9D%90%9C%F0%9D%90%A4%F0%9D%90%9E%F0%9D%90%AB%F0%9D%90%9F%F0%9D%90%A2%F0%9D%90%A5%F0%9D%90%9E – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

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