DevOps Tools: Docker, Jenkins, and Git Cheat Sheet

Ashwini DaveSeptember 9th, 2024Last Updated: September 11th, 2024

0 303 12 minutes read

Introduction

In the world of DevOps, efficiency and automation are the keys to success. Whether you’re managing containers with Docker, orchestrating them with Kubernetes, automating builds with Jenkins, or keeping track of your code with Git, each tool plays a critical role in streamlining your workflow. However, these tools can be complex, with a myriad of commands and configurations to remember. That’s where a cheat sheet comes in handy!

This guide is designed to give you a quick reference to the most essential commands and best practices for Docker, Kubernetes, Jenkins, and Git. Whether you’re a beginner looking to get started or a seasoned pro needing a refresher, this cheat sheet has something for everyone. Let’s dive in and make your DevOps journey smoother and more efficient!

Docker Cheat Sheet

Here’s a quick reference to help you navigate Docker’s core features and commands.

Installation and Setup

Platform	Info	Command
General	Install Docker Engine on your system.	Follow Docker’s Installation Guide.
Linux	Install Docker using the package manager.	sudo apt-get install docker-ce
macOS	Install Docker Desktop.	brew install –cask docker
Windows	Install Docker Desktop.	Docker Desktop for Windows

Installation And Setup

Docker Images: Pull, Build, and List Commands

Task	Command	Description
Pull an Image	docker pull <image_name>	Downloads a Docker image from Docker Hub.
Pull a Specific Version	docker pull <image_name>:<tag>	Downloads a specific version of an image (e.g., nginx:alpine).
Build an Image	docker build -t <image_name> .	Builds an image from a Dockerfile in the current directory.
Tag an Image	docker tag <image_id> <repository>:<tag>	Tags an existing image with a new repository and tag.
List Images	docker images	Displays all Docker images stored locally.
Remove an Image	docker rmi <image_id>	Deletes a specific image from local storage.
Inspect an Image	docker inspect <image_name>	Displays detailed information about an image.

Docker Images

Containers: Create, Start, Stop, and Remove

Task	Command	Description
Create and Start a Container	docker run -d –name <container_name> <image_name>	Creates and starts a container in detached mode.
Run a Container with Ports	docker run -d -p <host_port>:<container_port> <image_name>	Runs a container with specific port mapping.
Run a Container with Environment Variables	docker run -d -e <env_var>=<value> <image_name>	Runs a container with environment variables.
Start an Existing Container	docker start <container_name>	Starts a previously stopped container.
Stop a Running Container	docker stop <container_name>	Gracefully stops a running container.
Restart a Container	docker restart <container_name>	Restarts a container.
Remove a Container	docker rm <container_name>	Removes a stopped container.
View Running Containers	docker ps	Lists all currently running containers.
View All Containers	docker ps -a	Lists all containers, including stopped ones.
Inspect a Container	docker inspect <container_name>	Displays detailed information about a container.
View Container Logs	docker logs <container_name>	Displays logs generated by a container.

Containers

Docker Networking Basics: Creating and Managing Networks

Task	Command	Description
Create a Network	docker network create <network_name>	Creates a new Docker network for containers.
List Networks	docker network ls	Lists all Docker networks.
Inspect a Network	docker network inspect <network_name>	Displays detailed information about a specific network.
Connect a Container to a Network	docker network connect <network_name> <container_name>	Connects a running container to the specified network.
Disconnect a Container from a Network	docker network disconnect <network_name> <container_name>	Disconnects a container from the specified network.
Remove a Network	docker network rm <network_name>	Deletes a Docker network.
Run Container on Specific Network	docker run –network <network_name> <image_name>	Starts a container attached to a specific network.
Create Network with Subnet	docker network create –subnet=<subnet> <network_name>	Creates a network with a specified subnet (e.g., –subnet=192.168.1.0/24).

Docker Networking

Advanced Docker Commands

Docker Compose: Setting Up Multi-Container Environments

Task	Command	Description
Install Docker Compose	sudo apt-get install docker-compose	Installs Docker Compose on your system.
Create a Docker Compose File	touch docker-compose.yml	Creates a docker-compose.yml file to define multi-container setups.
Start Services Defined in Docker Compose	docker-compose up	Starts all services defined in the docker-compose.yml file.
Start in Detached Mode	docker-compose up -d	Starts services in the background (detached mode).
Stop Services	docker-compose down	Stops all running services and removes the containers.
List Running Services	docker-compose ps	Lists all running services managed by Docker Compose.
View Logs for All Services	docker-compose logs	Displays combined logs from all services.
Scale Services	docker-compose up –scale <service_name>=<number>	Scales a service to the specified number of instances.
Rebuild Services	docker-compose up –build	Rebuilds the images for all services before starting.
Remove Stopped Containers and Networks	docker-compose down –volumes	Removes containers, networks, and volumes created by up.

Docker Compose

Docker Volumes: Creating and Using Volumes

Task	Command	Description
Create a Volume	docker volume create <volume_name>	Creates a new named volume.
List Volumes	docker volume ls	Lists all Docker volumes on the system.
Inspect a Volume	docker volume inspect <volume_name>	Provides detailed information about a specific volume.
Mount a Volume to a Container	docker run -d -v <volume_name>:/path/in/container <image_name>	Mounts a volume to a specific path inside a container.
Mount a Host Directory as a Volume	docker run -d -v /path/on/host:/path/in/container <image_name>	Mounts a host directory as a volume inside the container.
Remove a Volume	docker volume rm <volume_name>	Removes a specific volume.
Remove Unused Volumes	docker volume prune	Deletes all volumes not used by at least one container.

Docker Volumes

Dockerfile: Basic Syntax and Best Practices

Instruction	Syntax	Description
Specify Base Image	FROM <image_name>:<tag>	Defines the base image for the Dockerfile.
Set Working Directory	WORKDIR /path/to/directory	Sets the working directory for subsequent instructions.
Copy Files to Container	COPY <source_path> <destination_path>	Copies files from the host to the container’s filesystem.
Run Commands in Container	RUN <command>	Executes commands in the container during the build process (e.g., RUN apt-get update).
Set Environment Variables	ENV <key>=<value>	Defines environment variables inside the container.
Expose Ports	EXPOSE <port_number>	Specifies which ports the container listens on at runtime.
Define Default Command	CMD [“executable”, “param1”, “param2”]	Sets the default command to run when the container starts.
Set Build Arguments	ARG <variable_name>=<default_value>	Defines variables that users can pass at build-time (e.g., ARG version=latest).
Best Practice: Use .dockerignore	.dockerignore	Use a .dockerignore file to exclude files and directories from being copied into the image.
Best Practice: Minimize Layers	Combine commands like RUN apt-get update && apt-get install -y <package>	Reduces the number of layers in the image, improving efficiency.

Dockerfile

Useful Tips and Best Practices

Debugging Containers

Task	Command/Practice	Description
Attach to a Running Container	docker attach <container_name>	Connects your terminal to a running container for real-time interaction.
Run a Container in Interactive Mode	docker run -it <image_name> /bin/bash	Starts a container and provides an interactive shell session.
Inspect Container State	docker inspect <container_name>	Provides detailed information about a container’s configuration and state.
Check Resource Usage	docker stats <container_name>	Monitors real-time resource usage (CPU, memory, etc.) for containers.
View Container Logs	docker logs <container_name>	Displays the logs generated by a container’s application.
Tail Container Logs	docker logs -f <container_name>	Follows (tails) the logs of a running container in real-time.
Execute a Command in a Running Container	docker exec -it <container_name> <command>	Executes a specific command inside a running container.
Use Debugging Tools in Container	Use images like alpine with RUN apk add –no-cache <package>	Install debugging tools inside the container for troubleshooting.

Debugging Containers

Best Practices for Debugging Containers:

Use docker exec for On-the-Fly Debugging: This allows you to run commands in a running container without stopping it.
Leverage Multi-Stage Builds for Debugging: Include debugging tools only in the development stages of your Dockerfile.
Keep Logs Accessible: Configure containers to output logs to a location where they can be easily accessed and monitored.
Test Containers in Isolation: Ensure that containers work correctly on their own before integrating them into larger systems.

Managing Logs

Task	Command/Practice	Description
Configure Log Driver	docker run –log-driver=<driver> <image_name>	Sets the logging driver (e.g., json-file, syslog) for a container.
Limit Log Size	docker run –log-opt max-size=10m –log-opt max-file=3 <image_name>	Limits log file size and sets a rotation policy.
Redirect Logs to Host File	docker run -v /path/on/host:/path/in/container <image_name>	Mounts a host directory for container logs.
View Logs for All Containers	docker logs –tail 100 -f $(docker ps -q)	Shows the latest 100 lines of logs for all running containers.
Clear Logs	`docker logs -f <container_name>	tee /dev/null`

Managing Logs

Best Practices for Managing Logs:

Implement Log Rotation: Use log drivers with rotation policies to prevent logs from consuming excessive disk space.
Centralize Logs: Use a centralized logging system (e.g., ELK stack, Fluentd) to aggregate and analyze logs from multiple containers.
Monitor Log Levels: Configure different log levels (info, warning, error) to avoid clutter and focus on relevant information.
Regularly Review Log Storage: Ensure that log files do not grow indefinitely and are archived or rotated as needed.

Performance Tuning

Task	Command/Practice	Description
Limit CPU and Memory Usage	docker run –memory=”500m” –cpus=”1.0″ <image_name>	Restricts the amount of memory and CPU a container can use.
Optimize Image Size	Use docker build –squash	Reduces image size by squashing layers during build.
Use Efficient Base Images	FROM alpine:latest	Select minimal base images (e.g., Alpine) to reduce image size and improve performance.
Use Docker’s Resource Limits	Configure resource limits in docker-compose.yml	Set limits in Compose files to manage resource allocation.
Monitor Container Performance	Use docker stats or third-party monitoring tools	Regularly check resource usage and adjust as needed.

Performance Tuning

Best Practices for Performance Tuning:

Optimize Dockerfile: Minimize the number of layers and use multi-stage builds to keep images lean.
Adjust Resource Limits: Tailor CPU and memory limits based on application needs to ensure optimal performance.

Jenkins Cheat Sheet

Getting Started with Jenkins – Installation and Setup

Task	Command/Practice	Description
Install Jenkins	`wget -q -O – https://pkg.jenkins.io/debian/jenkins.io.key	sudo apt-key add -<br>echo deb http://pkg.jenkins.io/debian-stable binary
Start Jenkins Service	sudo systemctl start jenkins	Starts the Jenkins service.
Check Jenkins Status	sudo systemctl status jenkins	Checks the status of the Jenkins service.
Access Jenkins Web Interface	Open http://localhost:8080 in a web browser	Access Jenkins’ web interface to complete setup.
Unlock Jenkins	Follow instructions at http://localhost:8080 to retrieve the initial admin password from /var/lib/jenkins/secrets/initialAdminPassword	Provides initial setup instructions and admin password.
Upgrade Jenkins	sudo apt-get updatesudo apt-get upgrade jenkins	Upgrades Jenkins to the latest version.

Installation And Setup

Overview of Jenkins Architecture and Components

Component	Description
Jenkins Master	The central server that coordinates the build process. It manages jobs, schedules tasks, and provides the user interface.
Jenkins Agent (Slave)	Machines configured to run build jobs dispatched by the Jenkins Master. They can run on various platforms and distribute the workload.
Build Jobs	The core unit of work in Jenkins, defining tasks such as building software or running tests.
Pipelines	Define the entire build and deployment workflow as code using a Jenkinsfile, automating complex workflows.
Plugins	Extend Jenkins’ functionality, including integrations with version control systems, build tools, and notifications.

Jenkins Architecture

Basic Jenkins Commands

Task	Command	Description
Create a New Job	Through Web UI: Click “New Item”	Initiates the creation of a new Jenkins job.
Build a Job	Click “Build Now” in job view	Starts a build of the selected job.
Delete a Job	Through Web UI: Click “Delete Project”	Removes a Jenkins job from the system.
Configure a Job	Through Web UI: Click “Configure”	Opens the configuration page for a job.
Manage Plugins	Through Web UI: Go to “Manage Jenkins””Manage Plugins”	Access the plugin management interface.
View Build History	Through Web UI: Click on a job, then “Build History”	Displays the history of builds for a job.
Pause/Resume a Job	Through Web UI: Click “Build Now” and “Pause” or “Resume”	Manages job execution to control build activity.
Schedule a Build	In Job Configuration: Set “Build Triggers”	Configures periodic builds or builds triggered by SCM changes.

Basic Jenkins Commands

Advanced Jenkins Configuration

Task	Command/Practice	Description
Create a Pipeline Job	Through Web UI: Click “New Item””Pipeline”	Creates a new pipeline job for advanced build processes.
Define a Jenkinsfile	Write Jenkinsfile in the root of your repository	Defines the build pipeline as code.
Integrate with Git	Through Web UI: Configure Source Code Management in job settings	Connects Jenkins to a Git repository for source code retrieval.
Integration with Docker	Install Docker pluginConfigure “Docker” in job settings	Allows Jenkins to build and deploy Docker containers.
Integration with Kubernetes	Install Kubernetes pluginConfigure “Kubernetes” in job settings	Manages Kubernetes clusters for scaling Jenkins builds.
Setup CI/CD Pipelines	Through Web UI: Define stages and steps in Jenkinsfile	Automates the build, test, and deployment pipeline.
Install Jenkins Plugins	Through Web UI: Go to “Manage Jenkins””Manage Plugins”	Adds functionality to Jenkins by installing plugins.
Configure Global Security	Through Web UI: Go to “Manage Jenkins””Configure Global Security”	Configures security settings, including user roles and permissions.
Backup Jenkins Configuration	Manually backup /var/lib/jenkins or use plugins like “ThinBackup”	Ensures you have a backup of Jenkins data and configurations.

Advanced Configuration

Creating and Configuring Jobs

Task	Command/Practice	Description
Create a New Freestyle Job	Through Web UI: Click “New Item””Freestyle project”	Sets up a new freestyle project for simple builds.
Create a New Pipeline Job	Through Web UI: Click “New Item””Pipeline”	Creates a new pipeline job for complex workflows.
Configure Job Triggers	In Job Configuration: Set “Build Triggers”	Defines triggers for automated builds, like SCM polling.
Set Up Build Steps	In Job Configuration: Define “Build” steps	Adds steps to build, test, and deploy the project.
Add Post-Build Actions	In Job Configuration: Define “Post-build Actions”	Configures actions to perform after the build completes.
Configure Notifications	In Job Configuration: Set “Post-build Actions”	Configures notifications to alert on build status changes.

Creating And Configuring Jobs

Managing Jenkins Pipelines: Setup and Execution

Task	Command/Practice	Description
Create a Pipeline Job	Through Web UI: Click “New Item””Pipeline”	Creates a new pipeline job for advanced build processes.
Define Stages in Jenkinsfile	Write stages in Jenkinsfile in the repository	Structures the build pipeline into distinct stages.
Execute a Pipeline Build	Click “Build Now” in the pipeline job view	Starts the pipeline build process.
View Pipeline Execution	Through Web UI: Click on a pipeline job, then “Pipeline Steps”	Monitors the execution and stages of the pipeline.
Manage Pipeline Parameters	In Pipeline Configuration: Define parameters	Configures parameters to customize pipeline builds.
Pipeline Visualization	Through Web UI: View “Pipeline Graph”	Provides a visual representation of pipeline execution.

Managing Jenkins Pipelines

Jenkinsfile: Syntax and Best Practices

Aspect	Description	Example
Basic Syntax	Defines the pipeline stages and steps in code.	pipeline { … }
Declarative Pipeline	Provides a structured format for defining pipelines.	pipeline { agent any stages { stage(‘Build’) { steps { echo ‘Building…’} } } }
Scripted Pipeline	Offers a more flexible, programmatic approach.	node { stage(‘Build’) { echo ‘Building…’} }
Environment Variables	Use environment block to define variables.	environment { MY_VAR = ‘value’ }
Error Handling	Use try/catch for handling errors.	try { … } catch { … }
Parallel Stages	Run stages in parallel for efficiency.	stages { stage(‘Parallel’) { parallel { stage(‘A’) { … } stage(‘B’) { … } } } }
Version Control	Store Jenkinsfile in version control for consistency.	Jenkinsfile in Git repository.

Jenkinsfile

Maintenance Tips

Task	Command/Practice	Description
Backup and Restore Strategies	Use plugins like “ThinBackup”Manual backup of /var/lib/jenkins	Ensures Jenkins data and configurations are preserved.
Monitoring Jenkins Performance	Install monitoring plugins like “Prometheus”	Tracks and analyzes Jenkins performance metrics.
Securing Jenkins: User Roles and Permissions	Through Web UI: Go to “Manage Jenkins””Configure Global Security”	Manages user roles, permissions, and security settings.

Maintenace Tips

Git Cheat Sheet

Basic Git Commands

Task	Command	Description
Installation and Setup	Installation varies by OS	Follow specific installation instructions for your operating system.
Clone a Repository	git clone <repo-url>	Creates a local copy of a remote repository.
Initialize a New Repository	git init	Initializes a new Git repository in the current directory.
Check Repository Status	git status	Displays the status of changes in the working directory.
View Commit History	git log	Shows the commit history for the repository.
Add Changes to Staging Area	git add <file>git add .	Adds specified files or all files to the staging area.
Commit Changes	git commit -m “message”	Commits staged changes with a descriptive message.
Push Changes to Remote Repository	git push origin <branch>	Pushes commits to the specified branch on a remote repository.
Pull Changes from Remote Repository	git pull origin <branch>	Fetches and merges changes from the remote repository to the local branch.
Create a New Branch	git branch <branch-name>	Creates a new branch in the repository.
Switch to a Branch	git checkout <branch-name>	Switches to the specified branch.
Merge Branches	git merge <branch-name>	Merges changes from the specified branch into the current branch.
Delete a Branch	git branch -d <branch-name>	Deletes the specified branch.

Basic Git Commands

Advanced Git Operations

Task	Command	Description
Merging Branches	git merge <branch-name>	Merges the specified branch into the current branch.
Rebasing	git rebase <branch-name>	Re-applies commits from the current branch onto the specified branch.
Resolve Merge Conflicts	Edit conflicting filesgit add <file>git commit	Manually resolve conflicts, add resolved files, and commit.
Create a Tag	git tag <tag-name>	Creates a new tag pointing to the current commit.
List Tags	git tag	Lists all tags in the repository.
Delete a Tag	git tag -d <tag-name>	Deletes a tag from the local repository.
Fetch Changes from Remote	git fetch origin	Retrieves updates from the remote repository but does not merge.
Pull Changes from Remote	git pull origin <branch>	Fetches and merges changes from the remote branch into the local branch.
Push Changes to Remote	git push origin <branch>	Pushes commits from the local branch to the remote branch.

Advanced Git Operations

Collaboration Tips

Git Workflows
- Gitflow: Utilizes a structured approach with branches like master, develop, and feature branches for managing releases and features.
- Feature Branches: Develop new features or fixes in separate branches to keep the main branch stable.
- Pull Requests: Use pull requests to review and merge changes, ensuring code quality and collaboration.
Managing Large Repositories with Git LFS (Large File Storage)
- Install Git LFS: git lfs install
- Track Large Files: git lfs track “*.filetype”
- Add and Commit: Use standard Git commands; Git LFS manages the large files.
- Push and Pull: Use git push and git pull as usual; Git LFS handles the large files separately.
Handling Submodules
- Add Submodule: git submodule add <repo-url> <path>
- Update Submodule: git submodule update –remote
- Remove Submodule: Edit .gitmodules and .git/config to remove references, then delete the submodule directory.

Best Practices for Integration

CI/CD Pipeline Setup
- Jenkins Pipeline Configuration
  - Define pipeline stages: Build, Test, Deploy.
  - Use Jenkins Pipelines (Declarative or Scripted) for automation.
- Docker Integration
  - Build and tag Docker images in Jenkins.
  - Optimize Dockerfiles to reduce image size and build time.
- Kubernetes Deployment
  - Deploy Docker containers using Kubernetes manifests or Helm charts.
  - Configure Kubernetes for scaling and managing applications.
Version Control with Git
- Branching Strategy
  - Implement strategies like Gitflow or GitHub Flow for feature development and releases.
- Commit and Pull Requests
  - Use clear commit messages and enforce code reviews through pull requests.
- Merge and Conflict Resolution
  - Handle merge conflicts carefully and review changes before merging.
Containerization and Orchestration
- Security and Optimization
  - Regularly scan Docker images for vulnerabilities.
  - Use environment variables for configuration; avoid hardcoding sensitive data.
- Resource Management
  - Define resource requests and limits in Kubernetes to manage cluster resources efficiently.
Infrastructure as Code (IaC)
- Provisioning
  - Use tools like Terraform or Ansible for automated infrastructure provisioning.
- Version Control
  - Store IaC scripts in Git repositories to track changes and maintain consistency.
Continuous Testing
- Integration in Pipeline
  - Incorporate automated tests into the Jenkins pipeline (unit, integration, end-to-end).
- Test Coverage
  - Monitor and aim for high test coverage to identify issues early.
Monitoring and Logging
- Centralized Logging
  - Aggregate logs using solutions like ELK Stack or Fluentd.
- Performance Monitoring
  - Collect and visualize metrics using tools like Prometheus and Grafana.
Security Practices
- Access Control
  - Implement role-based access controls (RBAC) in Jenkins, Docker, and Kubernetes.
- Secrets Management
  - Use secure methods for managing secrets, such as Kubernetes Secrets or encrypted environment variables.

Conclusion

Docker, Kubernetes, Jenkins, and Git each play a crucial role in modern DevOps practices. Docker facilitates consistent environments through containerization, Kubernetes manages and scales these containers, Jenkins automates CI/CD pipelines, and Git provides robust version control and collaboration.

These tools collectively streamline development processes, ensure consistency across environments, and enhance scalability and collaboration, driving efficiency and reliability in software delivery.

Resources

Docker Ecosystem: Docker Ecosystem – Docker is a containerization platform, quickly gaining ground in DevOps as a one-stop solution for all development needs.
Docker Cleanup: Docker cleanup quick tutorial – This quick tutorial shows the different ways to rid your system of unused and unnecessary Docker files and enable smoother system performance.
Microservice Architecture in Docker: Building apps using Microservice Architecture in Docker – Docker has many pros but comes with unique cons. Learn how to use Microservice in Docker with tutorial!
Docker Documentation: https://docs.docker.com – The official Docker documentation provides comprehensive guides, tutorials, and reference material to help you get started with Docker and its advanced features.
Jenkins User Documentation: https://www.jenkins.io/doc/ – Jenkins offers detailed documentation on installing, configuring, and using Jenkins for continuous integration and continuous delivery (CI/CD).
Pro Git Book: https://git-scm.com/book/en/v2 – This free, open-source book is a great resource for mastering Git, from basic concepts to advanced techniques.

DevOps Tools: Docker, Jenkins, and Git Cheat Sheet

Introduction