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

1. Create Directories Using Shell Script

2. Create a Script to Backup All Your Work

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

4. Read About User Management

1. Create Directories Using Shell Script

You need a script called createDirectories.sh that takes three arguments: a directory name prefix, a starting number, and an ending number. Here’s how you can write that script:

#!/bin/bash

# Check if the correct number of arguments is provided
if [ "$#" -ne 3 ]; then
    echo "Usage: $0 <directory_name> <start_number> <end_number>"
    exit 1
fi

dir_name=$1
start_num=$2
end_num=$3

# Create directories using a loop
for (( i=start_num; i<=end_num; i++ ))
do
    mkdir "${dir_name}${i}"
done

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

Usage:

Make it executable chmod +x createDirectories.sh

• To create directories from day1 to day90:

    ./createDirectories.sh day 1 90
  

• To create directories from Movie20 to Movie50:

    ./createDirectories.sh Movie 20 50
  

2. Create a Script to Backup All Your Work

Here's an example backup script named backup.sh. This script creates a backup of a specified directory to a backup location:

#!/bin/bash

# Variables
SOURCE_DIR="$1"    # Directory to backup
BACKUP_DIR="$2"    # Backup destination

# Check if the correct number of arguments is provided
if [ "$#" -ne 2 ]; then
    echo "Usage: $0 <source_directory> <backup_directory>"
    exit 1
fi

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

# Create a timestamp
TIMESTAMP=$(date +"%Y%m%d_%H%M%S")

# Backup using tar
tar -czf "$BACKUP_DIR/backup_$TIMESTAMP.tar.gz" "$SOURCE_DIR"

echo "Backup of $SOURCE_DIR completed at $BACKUP_DIR/backup_$TIMESTAMP.tar.gz."

Usage: To run the backup script:

 ./backup.sh /path/to/source /path/to/backup

To automate the backup script using cron, you would do the following:

A crontab command allows users to submit, edit, or delete entries to cron. A crontab file is a user file that holds the scheduling information.

• Cron is a job scheduler utility, In simple terms it executes described commands/scripts at a particular predefined interval.

  crontab is a table in which we maintain all the cron jobs that we need to execute in our system.

• command to check the crontab list:

      crontab -l
  

create a new cron job and when you run this command the first time it will ask you to select an editor like nano, vim, etc, and then select the editor as per your choice and add a new line in the file:

• Open the crontab configuration for editing:

     crontab -e
  

• Add a cron job entry. For example, to run the backup script every day at 2 AM:

    0 2 * * * /path/to/backup.sh /path/to/source /path/to/backup
  

4. Create 2 Users and Display Their Usernames

You can create users using the useradd command. Here’s how you can create a simple script createUsers.sh to create two users:

#!/bin/bash

# Creating two users
useradd user1
useradd user2

# Display the usernames
echo "Created users:"
echo "User 1: user1"
echo "User 2: user2"

Usage: To create the users, run:

./createUsers.sh

Summary

• createDirectories.sh: Creates directories with a specified prefix and range.

• backup.sh: Backups a specified directory to a designated backup location.

• Cron: Automates the backup process by scheduling it using crontab.

• createUsers.sh: Creates two users and displays their usernames

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