You can use a shell script to check the status of a service. Here's an example to check if nginx is running:

#!/bin/bash

SERVICE="nginx"

if systemctl is-active --quiet $SERVICE; then
  echo "$SERVICE is running."
else
  echo "$SERVICE is not running."
fi

This script monitors disk usage and sends an alert if any partition exceeds 80%.

#!/bin/bash

THRESHOLD=80

df -h | awk 'NR>1 {if ($5+0 > ENVIRON["THRESHOLD"]) print $0}' | while read line; do
  echo "Alert: Disk usage exceeded threshold: $line"
done

Using Python and the requests library, you can check the status of a web application.

import requests

url = "http://example.com"
try:
    response = requests.get(url)
    if response.status_code == 200:
        print(f"Website {url} is up.")
    else:
        print(f"Website {url} is down. Status code: {response.status_code}")
except requests.exceptions.RequestException as e:
    print(f"Error connecting to {url}: {e}")

This Dockerfile sets up a Flask web application.

# Use the official Python image
FROM python:3.9-slim

# Set the working directory
WORKDIR /app

# Copy the application files
COPY . /app

# Install dependencies
RUN pip install -r requirements.txt

# Expose the application port
EXPOSE 5000

# Run the application
CMD ["python", "app.py"]

Example app.py:

from flask import Flask

app = Flask(__name__)

@app.route('/')
def hello():
    return "Hello, DevOps!"

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=5000)

Here’s an example of a shell script to back up a MySQL database:

#!/bin/bash

DB_NAME="my_database"
DB_USER="root"
DB_PASS="password"
BACKUP_DIR="/backup"
DATE=$(date +%F)

mkdir -p $BACKUP_DIR

mysqldump -u $DB_USER -p$DB_PASS $DB_NAME > $BACKUP_DIR/$DB_NAME-$DATE.sql

if [ $? -eq 0 ]; then
  echo "Backup successful: $BACKUP_DIR/$DB_NAME-$DATE.sql"
else
  echo "Backup failed!"
fi

This script continuously monitors and restarts a service if it stops running.

#!/bin/bash

SERVICE="nginx"

while true; do
  if ! systemctl is-active --quiet $SERVICE; then
    echo "$SERVICE is down. Restarting..."
    systemctl restart $SERVICE
  fi
  sleep 30
done

This Ansible playbook installs Apache and ensures it’s running.

---
- name: Install and start Apache
  hosts: all
  become: yes

  tasks:
    - name: Install Apache
      apt:
        name: apache2
        state: present
        update_cache: yes

    - name: Start Apache service
      service:
        name: apache2
        state: started
        enabled: yes

This Jenkinsfile defines a pipeline to build and deploy a Java app.

pipeline {
    agent any

    stages {
        stage('Build') {
            steps {
                echo 'Building the application...'
                sh './gradlew build'
            }
        }
        stage('Test') {
            steps {
                echo 'Running tests...'
                sh './gradlew test'
            }
        }
        stage('Deploy') {
            steps {
                echo 'Deploying the application...'
                sh 'scp build/libs/app.jar user@server:/deployments'
            }
        }
    }
}

This Terraform configuration creates an AWS EC2 instance.

provider "aws" {
  region = "us-east-1"
}

resource "aws_instance" "example" {
  ami           = "ami-0c55b159cbfafe1f0" # Replace with a valid AMI
  instance_type = "t2.micro"

  tags = {
    Name = "DevOps-Instance"
  }
}

This script uploads a file to an S3 bucket.

import boto3

s3 = boto3.client('s3')

bucket_name = "my-bucket"
file_name = "file.txt"

try:
    s3.upload_file(file_name, bucket_name, file_name)
    print(f"{file_name} uploaded to {bucket_name}.")
except Exception as e:
    print(f"Error: {e}")