Day 5. Advanced Linux Shell Scripting for DevOps Engineers with User Management

Welcome to day 5 of the #90daysDevOpschallenge, our focus today is diving into advanced Linux shell scripting, focusing on advanced user management an integral part for anyone who's a DevOps Engineer.

On day 5, we will work on user management tasks like,

• Create Directories using Shell Script (bulk user creation)
• Create a Script to Backup All Your Work

1. Create Directory

**

!/bin/bash

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

# Assign arguments to variables
base_name=$1
start=$2
end=$3

# Loop through the range and create directories
for ((i=start; i<=end; i++)); do
  dir="${base_name}${i}"
  mkdir -p "$dir"
  echo "Created directory: $dir"
done

./createDirectories.sh day 1 90

./createDirectories.sh Movie 20 50

Output

Created directory: day1
Created directory: day2
...
Created directory: day90

The script automatically creates a series of directories using a base name and a range of numbers.

1. Create Script to back up your work

#!/bin/bash
# Set variables
SOURCE_DIR="$HOME/work"                 # Change 'work' to your actual folder name
BACKUP_DIR="$HOME/backups"
TIMESTAMP=$(date +"%Y%m%d_%H%M%S")
BACKUP_FILE="backup_$TIMESTAMP.tar.gz"

# Create backup directory if it doesn't exist
mkdir -p "$BACKUP_DIR"

# Create a compressed archive of the source directory
tar -czvf "$BACKUP_DIR/$BACKUP_FILE" "$SOURCE_DIR"

# Notify user
echo "✅ Backup complete: $BACKUP_DIR/$BACKUP_FILE"

What This Script Does:
Looks for a directory named work in your home folder.

Compresses its contents into a .tar.gz archive.

Stores the backup in a backups folder (also in your home directory).

Names the backup file using the current date and time for easy identification.

1. Create Users and Display their names

#!/bin/bash

# Create two users
sudo adduser user1
sudo adduser user2

# Display the created usernames
echo "Created Users:"
cut -d: -f1 /etc/passwd | grep -E 'user1|user2'

Explanation

adduser creates a new user account.

/etc/passwd stores user account info.

cut -d: -f1 extracts just the usernames from each line.

grep -E 'user1|user2' filters to show only user1 and user2

1. What is Cron? Cron is a time-based job scheduler in Unix/Linux systems. It lets you schedule tasks (called cron jobs) to run automatically at specified intervals — like daily, weekly, or even every minute.

What is Crontab?
Crontab (short for "cron table") is the file where you define these scheduled tasks. Each line in a crontab file represents a separate job and tells the system:

“Run this command at this time.”

Why is this Important in DevOps?
DevOps engineers use cron to automate repetitive tasks like:

• Running backups

• Cleaning up logs

• Running health checks

• Deploying scripts
  

* * * * * command_to_run
│ │ │ │ │
│ │ │ │ └─ Day of week (0 - 7) (Sunday = 0 or 7)
│ │ │ └─── Month (1 - 12)
│ │ └───── Day of month (1 - 31)
│ └─────── Hour (0 - 23)
└───────── Minute (0 - 59)