Day 9 Task: Shell Scripting Challenge Directory Backup with Rotation

Bash Scripting Challenge: Backup with Rotation

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Welcome to this exciting Bash scripting challenge! Today, we'll create a script that performs a backup of a specified directory, includes timestamped backup folders, and implements a rotation mechanism to retain only the last 3 backups. Let's dive in!

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Challenge Description

Your task is to create a bash script that takes a directory path as a command-line argument and performs a backup of the directory. The script will:

• Create timestamped backup folders.

• Copy all files from the specified directory into the backup folder.

• Implement a rotation mechanism to keep only the last 3 backups, removing the oldest backups.

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Example Usage

Assume the script is named backup_with_rotation.sh. Below is an example of how it will look when executed on different dates.

First Execution (2023-07-30):

$ ./backup_with_rotation.sh /home/user/documents

Output:

Backup created: /home/user/documents/backup_2023-07-30_12-30-45
Backup created: /home/user/documents/backup_2023-07-30_15-20-10
Backup created: /home/user/documents/backup_2023-07-30_18-40-55

Directory Contents After Execution:

backup_2023-07-30_12-30-45
backup_2023-07-30_15-20-10
backup_2023-07-30_18-40-55
file1.txt
file2.txt
...

Second Execution (2023-08-01):

$ ./backup_with_rotation.sh /home/user/documents

Output:

Backup created: /home/user/documents/backup_2023-08-01_09-15-30

Directory Contents After Execution:

backup_2023-07-30_15-20-10
backup_2023-07-30_18-40-55
backup_2023-08-01_09-15-30
file1.txt
file2.txt
...

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The Script

Here's the complete backup_with_rotation.sh script that incorporates all the tasks mentioned above.

#!/bin/bash

# Check if the directory path is provided as a command-line argument
if [ -z "$1" ]; then
    echo "Usage: $0 <directory_path>"
    exit 1
fi

# Assign the directory path to a variable
DIR=$1

# Create a timestamp for the backup folder name
TIMESTAMP=$(date +"%Y-%m-%d_%H-%M-%S")

# Create the backup folder inside the specified directory
BACKUP_DIR="$DIR/backup_$TIMESTAMP"
mkdir -p "$BACKUP_DIR"

# Copy all files from the specified directory into the backup folder
cp -r "$DIR"/* "$BACKUP_DIR"

# Output the backup creation message
echo "Backup created: $BACKUP_DIR"

# Implement the rotation mechanism to keep only the last 3 backups
cd "$DIR"
BACKUPS=($(ls -d backup_* | sort))

# Check if there are more than 3 backups
if [ ${#BACKUPS[@]} -gt 3 ]; then
    # Calculate the number of backups to remove
    REMOVE_COUNT=$((${#BACKUPS[@]} - 3))

    # Remove the oldest backups
    for ((i=0; i<REMOVE_COUNT; i++)); do
        rm -rf "${BACKUPS[$i]}"
        echo "Removed old backup: ${BACKUPS[$i]}"
    done
fi

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Step-by-Step Explanation

1. Check for Command-line Argument: The script checks if a directory path is provided as an argument. If not, it displays usage instructions and exits.

2. Assign Directory Path to Variable: The provided directory path is assigned to the variable DIR.

3. Create Timestamp: A timestamp is generated for naming the backup folder using the date command.

4. Create Backup Folder: The script creates a backup folder inside the specified directory.

5. Copy Files to Backup Folder: All files from the specified directory are copied into the backup folder.

6. Output Backup Creation Message: The script outputs a message indicating the backup creation.

7. Implement Rotation Mechanism: The script navigates to the specified directory and lists all backup folders. If there are more than 3 backups, it calculates the number of backups to remove and deletes the oldest backups.

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Example Screenshots

Execution and Output:

Directory Contents After Execution:

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Conclusion

This script helps in automating the backup process and ensures that only the last 3 backups are retained. It's a simple yet effective way to manage backups in a directory. Happy scripting! 🚀