Day 28: Docker - Building and managing images

Debakar Roy included in DevOps Software Development Automation Infrastructure Containerization Docker

2023-05-16 1299 words 7 minutes

Contents

Content

Part 1: Introduction to DevOps

Part 2: Version Control Systems

Part 3: Continuous Integration and Continuous Deployment (CI/CD)

Part 4: Configuration Management

Part 5: Infrastructure as Code

Part 6: Containerization

Day 26: Introduction to containerization
Day 27: Docker - Installation and configuration
Day 28: Docker - Building and managing images
Day 29: Docker - Running and managing containers
Day 30: Docker Compose and best practices

Part 7: Container Orchestration

Day 31: Introduction to container orchestration
Day 32: Kubernetes - Architecture and components
Day 33: Kubernetes - Deployments, services, and storage
Day 34: Kubernetes - ConfigMaps and secrets
Day 35: Kubernetes - Best practices and Helm

Part 8: Monitoring and Logging

Day 36: Introduction to monitoring and logging
Day 37: Prometheus - Installation and configuration
Day 38: Prometheus - Querying and alerting
Day 39: Grafana - Installation and configuration
Day 40: ELK Stack (Elasticsearch, Logstash, Kibana) - Overview and comparison

Part 9: Cloud Platforms

Day 41: Introduction to cloud platforms
Day 42: AWS - EC2, S3, and RDS
Day 43: AWS - IAM, VPC, and ELB
Day 44: Azure - Virtual Machines, Storage, and SQL Database
Day 45: Google Cloud Platform - Compute Engine, Storage, and Cloud SQL

Part 10: DevOps Security

Day 46: Introduction to DevOps security
Day 47: Security best practices for CI/CD pipelines
Day 48: Infrastructure and application security
Day 49: Container and Kubernetes security
Day 50: Cloud security and compliance

Building docker image

A Docker image is a lightweight, standalone, and executable software package that includes everything needed to run a piece of software, including the code, runtime, system tools, libraries, and system dependencies. These images are built based on instructions provided in a Dockerfile, which contains a set of commands and configurations.

A Dockerfile might look something like this:

# This line specifies the base image for our Docker image. 
# In this case, we're using the official Python 3.9-slim image as the starting point.
FROM python:3.9-slim

# This sets the working directory inside the container to /app. 
# Any subsequent commands will be executed in this directory.
WORKDIR /app

# This copies the requirements.txt file from the host machine to the working directory of the container. 
# This file should contain the necessary Python dependencies for your FastAPI application.
COPY requirements.txt .

# This command installs the Python dependencies specified in the requirements.txt file using pip.
RUN pip install --no-cache-dir -r requirements.txt

# This copies the entire application code from the host machine to the working directory of the container.
COPY . .

# This instruction exposes port 7400 to allow communication with the FastAPI application running inside the container.
EXPOSE 7400

# This sets the default command to be executed when the container starts. 
# It uses the uvicorn server to run the FastAPI application specified in the main.py file, 
# and binds it to the host's IP address 0.0.0.0 on port 7400.
CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "7400"]

Once you have this Dockerfile in your project directory, you can use the docker build command to build the Docker image. For example:

docker build -t my-fastapi-app .

After successfully building the image, you can run a container using the image with the docker run command:

docker run -p 7400:7400 my-fastapi-app

This will start the container and bind port 7400 of the container to port 7400 of the host machine, allowing you to access the FastAPI application at http://localhost:7400.

Managing Docker images

Once you have built a Docker image, you can manage it efficiently using various Docker commands. Here are some essential Docker commands for image management:

docker tag: The docker tag command allows you to add a new tag to an existing image. Tags are labels that provide a human-readable and meaningful name to an image, making it easier to reference and manage.
docker images: This command lists all the Docker images present on your system along with their details such as the image ID, repository, tag, size, and creation date.
docker push: Once you have built your image and want to share it with others, you can use the docker push command. It allows you to push your local image to a remote registry, making it accessible to others.
docker pull: If you want to fetch an image from a remote registry, you can use the docker pull command. This command downloads the specified image from a registry like Docker Hub to your local machine.
docker rmi: If you want to remove an existing image from your local machine, you can use the docker rmi command followed by the image ID or repository name. This command helps you clean up unused or outdated images.

Example

# To add the "latest" tag to the Python FastAPI application image, you can use
$ docker tag my-fastapi-app my-fastapi-app:latest

# This command lists all the Docker images present on your local machine. 
# It displays the repository, tag, image ID, creation date, and size of each image.
$ docker images
REPOSITORY            TAG         IMAGE ID       CREATED       SIZE
myjenkins-blueocean   2.387.3-1   3eb5689ff763   6 days ago    790MB
my-fastapi-app        latest      67cdycd99743   2 hours ago   150MB
docker                dind        85cdec499643   8 days ago    323MB
postgres              latest      f14b0d96cff9   2 weeks ago   379MB
vault                 latest      1fa9c3f0708d   4 weeks ago   186MB

# This command fetches the latest version of the nginx image from the Docker Hub registry. 
# It downloads the image to your local machine.
$ docker pull nginx:latest
latest: Pulling from library/nginx
f03b40093957: Pull complete
eed12bbd6494: Pull complete
fa7eb8c8eee8: Pull complete
7ff3b2b12318: Pull complete
0f67c7de5f2c: Pull complete
831f51541d38: Pull complete
Digest: sha256:af296b188c7b7df99ba960ca614439c99cb7cf252ed7bbc23e90cfda59092305
Status: Downloaded newer image for nginx:latest
docker.io/library/nginx:latest

# This command pushes a local Docker image to a remote registry, making it available for others to use. 
# The output includes information about the pushed image, such as the digest and size.
$ docker push debakarr/myjenkins-blueocean:latest
The push refers to repository [docker.io/debakarr/myjenkins-blueocean]
ebe100ea75f2: Pushed
aa20ea415e9b: Pushed
dd7368f0b1ad: Pushed
6a2689aa4ed2: Pushed
9dfe2887b847: Pushed
ddabbb0c670a: Mounted from jenkins/jenkins
e2cf45412e4b: Mounted from jenkins/jenkins
12e639a5a7ea: Mounted from jenkins/jenkins
ba66619e71de: Mounted from jenkins/jenkins
d90c97aff719: Mounted from jenkins/jenkins
67ac8a362561: Mounted from jenkins/jenkins
6a45b66c291b: Mounted from jenkins/jenkins
56b018284c58: Mounted from jenkins/jenkins
7b8f9d0c670c: Mounted from jenkins/jenkins
3811da883895: Mounted from jenkins/jenkins
7de19ea2fded: Mounted from jenkins/jenkins
3fb287e008f8: Mounted from jenkins/jenkins
ae56c0c5405b: Mounted from jenkins/jenkins
latest: digest: sha256:97ce065841e7e33ac746396a46c4ef5865a772c2bd5b5651aa96b83951148f00 size: 4092

# This command removes a specified Docker image from your local machine. 
# The output confirms the successful removal of the image.
$ docker rmi nginx
Untagged: nginx:latest
Untagged: nginx@sha256:af296b188c7b7df99ba960ca614439c99cb7cf252ed7bbc23e90cfda59092305
Deleted: sha256:f9c14fe76d502861ba0939bc3189e642c02e257f06f4c0214b1f8ca329326cda
Deleted: sha256:419f8948c50c723f2a5ac74428af3d804b5d0079d6df8f7f827663cf10cbc366
Deleted: sha256:1030aac4f1a8096ed58d3d4a2df55dd1b1b27d919ad156d97ad1f68081d0051a
Deleted: sha256:7d90b49d96c3036539ef144ecc27c01de03902d8ea166a0f7b77d11d3779c4bd
Deleted: sha256:551acb210764654af31b6cd51adaa74edc9a202587c3395fe0e9f95a2e097f8b
Deleted: sha256:3c530958db4c75c6fb409f339367aaf9a1e163c84718c035d4b09bebc83f43e7
Deleted: sha256:8cbe4b54fa88d8fc0198ea0cc3a5432aea41573e6a0ee26eca8c79f9fbfa40e3

Reference: