Dockerfile Instructions And Docker Run Commands: A Comprehensive Guide

Docker has revolutionized containerization, making it essential for developers and IT professionals to master Dockerfile instructions and run commands. Below is a detailed breakdown of key Docker components, followed by practical examples.

Dockerfile Instructions

FROM: Sets the base image for the container.
```
FROM ubuntu:20.04 
```

RUN: Executes commands inside the container.

RUN apt-get update && apt-get install -y curl

MAINTAINER (Deprecated): Identifies the image creator (use LABEL instead).
LABEL: Adds metadata to the image.
```
LABEL maintainer="[email protected]" 
```
ADD: Copies files from a source (supports URLs and tar extraction).
```
ADD https://example.com/file.tar.gz /app/ 
```
COPY: Copies files without URL or extraction support.
```
COPY ./src /app/src 
```
VOLUME: Creates a shared mount point.
```
VOLUME /data 
```
EXPOSE: Specifies the container’s listening port.
```
EXPOSE 8080 
```
WORKDIR: Sets the working directory.
```
WORKDIR /app 
```
USER: Defines the user for running processes.
```
USER appuser 
```
STOPSIGNAL: Specifies the stop signal (default: SIGTERM).
```
STOPSIGNAL SIGKILL 
```
ENTRYPOINT: Sets the primary command.
```
ENTRYPOINT ["python", "app.py"] 
```
CMD: Sets default arguments for ENTRYPOINT.
```
CMD ["--port=8080"] 
```
ENV: Sets environment variables.
```
ENV DB_HOST=localhost 
```

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.
-t, –tty: Allocates a pseudo-TTY.
```
docker run -it ubuntu /bin/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 restart policy.
```
docker run --restart=always nginx 
```

Core Docker Concepts

Docker Image: A read-only template (e.g., nginx:latest).
Docker Container: A running instance of an image.
Docker Client: CLI tool (docker command).
Docker Daemon: Background service managing containers.
Docker Registry: Stores images (e.g., Docker Hub).

You Should Know:

1. Building and Running a Docker Container

docker build -t myapp:1.0 . 
docker run -d -p 8080:80 myapp:1.0

2. Managing Containers

docker ps -a  List all containers 
docker stop <ID>  Stop a container 
docker rm <ID>  Remove a container 
docker logs <ID>  View logs

3. Managing Images

docker images  List images 
docker rmi <ID>  Remove an image 
docker pull nginx  Download an image

4. Networking in Docker

docker network ls  List networks 
docker network create my_network 
docker run --network=my_network nginx

5. Docker Compose (Multi-Container Setup)

version: '3' 
services: 
web: 
image: nginx 
ports: 
- "80:80" 
db: 
image: mysql 
environment: 
MYSQL_ROOT_PASSWORD: password

Run with:

docker-compose up -d

What Undercode Say

Docker is a powerful tool for DevOps, cloud deployments, and microservices. Mastering `Dockerfile` instructions and `docker run` commands ensures efficient container management. Always follow best practices:
– Use `.dockerignore` to exclude unnecessary files.
– Prefer `COPY` over `ADD` unless URL/tar extraction is needed.
– Use multi-stage builds to reduce image size.
– Secure containers by running as non-root (USER instruction).

Expected Output:

A fully functional Dockerized application with optimized images, proper networking, and automated deployments.

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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Dockerfile Instructions and Docker Run Commands: A Comprehensive Guide