Understanding Linux Backup and Rotation with Scripts

In Linux, managing backups and handling large amounts of data efficiently is crucial. Two common tools for this are zip and tar, which compress files to save space. Here’s a simplified guide on how to create a backup script, manage backups with rotation, and schedule tasks using cron.

Creating a Backup Script

Start by Writing the Backup Script

We'll use a script to create backups of a directory. Open a terminal and create a new file named backup.sh using the vim editor:

 vim backup.sh

Enter the following script:

 #!/bin/bash
 # This script takes backup of a given directory
 # Usage: ./backup.sh <path_of_directory> <backup_directory>

 source_dir=$1    # The source directory to back up
 target_dir=$2    # The directory where backups will be saved
 timestamp=$(date '+%Y-%m-%d-%H-%M-%S')  # Current timestamp

 # Create backup
 backup_dir="${target_dir}/backup_${timestamp}"  # Backup file name with timestamp
 zip -r "${backup_dir}.zip" "${source_dir}"   # Compress and save

 if [ $? -eq 0 ]; then
     echo "Backup created successfully"
 else
     echo "Backup failed for $timestamp"
 fi

Save and exit vim by typing :wq.

Making the Script Executable

Before running the script, make it executable:
```
 chmod 700 backup.sh
```
Run the Backup Script

Execute the script to back up a directory:
```
 ./backup.sh /home/ubuntu/scripts /home/ubuntu/backups
```

Managing Backups with Rotation

Backup rotation helps in managing storage by keeping only a fixed number of the latest backups and removing older ones. Modify the script to include rotation:

Edit the Backup Script

Open backup.sh for editing:

 vim backup.sh

Update the script with rotation functionality:

 #!/bin/bash
 source_dir=$1
 target_dir=$2
 timestamp=$(date '+%Y-%m-%d-%H-%M-%S')

 # Create backup
 backup_dir="${target_dir}/backup_${timestamp}"
 zip -r "${backup_dir}.zip" "${source_dir}" >/dev/null

 if [ $? -eq 0 ]; then
     echo "Backup created successfully"
 else
     echo "Backup failed for $timestamp"
     exit 1
 fi

 # Perform rotation
 backups=($(ls -t "${target_dir}/backup_*.zip"))  # List backups sorted by date
 if [ "${#backups[@]}" -gt 5 ]; then
     backups_to_remove=("${backups[@]:5}")  # Get backups to remove
     for backup in "${backups_to_remove[@]}"; do
         rm "$backup"  # Remove old backups
     done
 fi

Save and exit vim by typing :wq.

Schedule the Backup Script Using Cron

To automate the backup process, use cron to run the script at regular intervals. Edit the crontab:
```
 crontab -e
```
Add the following line to schedule the backup to run every minute:
```
 * * * * * /path/to/backup.sh /home/ubuntu/scripts /home/ubuntu/backups >/dev/null 2>&1
```
This will run the backup script every minute and suppress any output or errors.

Understanding Key Commands

ls -t: Lists files sorted by modification time, with the newest files first.
ls -t | head -5: Shows the 5 most recent files.
>/dev/null: Redirects output to null, effectively discarding it.

By using these scripts and cron jobs, you can automate backups, manage disk space efficiently, and ensure you always have recent backups available.