Day 5 of 90DaysOfDevOps : Advanced Linux Shell Scripting for DevOps Engineers with User Management

1. Create Directories Using Shell Script:

• Write a bash script createDirectories.sh that, when executed with three arguments (directory name, start number of directories, and end number of directories), creates a specified number of directories with a dynamic directory name.

• Example 1: When executed as ./createDirectories.sh day 1 90, it creates 90 directories as day1 day2 day3 ... day90.

#!/bin/bash

# Check if three arguments are passed
if [ "$#" -ne 3 ]; then
    echo "Usage: $0 <directory_name> <start_number> <end_number>"
    exit 1
fi

# Assign arguments to variables
dir_name=$1
start_num=$2
end_num=$3

# Loop from start to end number
for (( i=start_num; i<=end_num; i++ ))
do
    mkdir "${dir_name}${i}"
done

echo "Directories created successfully from ${dir_name}${start_num} to ${dir_name}${end_num}."

2. Create a Backup Script

Backups are an important part of a DevOps Engineer's day-to-day activities. The video in the references will help you understand how a DevOps Engineer takes backups (it can feel a bit difficult but keep trying, nothing is impossible).

#!/bin/bash

# Define source and backup directory
src="/path/to/your/work"  # Change this path
backup_dir="/path/to/backup"  # Change this path
timestamp=$(date +"%Y%m%d%H%M%S")

# Create backup
tar -czvf "$backup_dir/backup_$timestamp.tar.gz" "$src"

echo "Backup completed at $backup_dir/backup_$timestamp.tar.gz"

3.Read About Cron and Crontab to Automate the Backup Script:

Cron is the system's main scheduler for running jobs or tasks unattended. A command called crontab allows the user to submit, edit, or delete entries to cron. A crontab file is a user file that holds the scheduling information.

Cron Setup:

• Open the crontab editor with crontab -e.

• It will run your backup script every 2 hours:

    0 0 * * * /path/to/backup_script.sh
  

4.Read About User Management:

• A user is an entity in a Linux operating system that can manipulate files and perform several other operations. Each user is assigned an ID that is unique within the system. IDs 0 to 999 are assigned to system users, and local user IDs start from 1000 onwards.

• Create 2 users and display their usernames.

    # Create two users
    sudo useradd tanjiro
    sudo useradd nezuko
  
    # Verify creation
    cat /etc/passwd | grep -E "tanjiro|nezuko"
  

  🚀 Conclusion

  These tasks offer a solid start to essential DevOps skills like automation, backup management, and user administration. 📂 Writing scripts to automate tasks, scheduling backups with Cron ⏰, and managing users 🧑‍💻 are all crucial for smooth, secure workflows. Completing these exercises boosts your confidence and builds a strong foundation for advanced DevOps tasks. Sharing your journey 📣 connects you with the DevOps community, adding more value as you learn and grow. Keep going—each step gets you closer to becoming a DevOps pro! 🌟

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