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)