Backup & Restore Guide (Verified Compressed Archives)

This guide walks you through setting up automated, scheduled backups for a Raspberry Pi using a compressed archive (.tar.gz) with post-creation verification, as well as how to restore a system from a backup file.

Why Choose This Method Over `dd`?

File-System Safe: rsync and tar operate cleanly on active file systems, avoiding disk corruption caused by live sector writes during dd clones.
Storage Efficient: Instead of creating a raw image matching your SD card size (e.g., 32–64 GB), compressed backups only archive actual files—typically resulting in backups of a few hundred megabytes to a few gigabytes.
Hardware Flexible: Restoring a dd image requires a target SD card of equal or larger capacity down to the exact sector count. File archives can be restored to an SD card of any size.
Fast & Verifiable: Automated checks confirm archive integrity immediately upon creation, allowing you to catch storage failures early.

Part 1: Backup Script Setup

1. Create the Script Directory

Create a directory for your custom scripts and open a new file named raspi_backup.sh:

mkdir -p ~/scripts
nano ~/scripts/raspi_backup.sh

2. Script Code

Paste the following code into ~/scripts/raspi_backup.sh. Update BACKUP_PATH to point to your external mount point if it differs.

#!/bin/bash

# Exit immediately if a command exits with a non-zero status
set -e

# Configuration
BACKUP_PATH="/mnt/external_disk/raspi_backups"
DATE=$(date +%Y-%m-%d)
ARCHIVE="$BACKUP_PATH/raspi_backup_$DATE.tar.gz"
TEMP_DIR="/tmp/raspi_backup_temp"

# Script directory and log path
SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
LOG_FILE="$SCRIPT_DIR/raspi_backup.log"

# Helper function to append ISO-timestamped log messages
log_message() {
  local MESSAGE="$1"
  echo "$(date '+%Y-%m-%d %H:%M:%S') - $MESSAGE" | tee -a "$LOG_FILE"
}

# Enforce strict backup path availability check
if [ ! -d "$BACKUP_PATH" ]; then
  echo "$(date '+%Y-%m-%d %H:%M:%S') - ERROR: Backup path '$BACKUP_PATH' is unavailable or incorrect." >> "$LOG_FILE"
  exit 1
fi

log_message "START: Beginning system backup to $ARCHIVE"

# Setup clean temporary workspace
rm -rf "$TEMP_DIR"
mkdir -p "$TEMP_DIR"
trap 'rm -rf "$TEMP_DIR"' EXIT

# Export installed package list
dpkg --get-selections > "$TEMP_DIR/package-list.txt"

# Create compressed system archive
tar -czpf "$ARCHIVE" \
  --warning=no-file-ignored \
  --exclude=/dev \
  --exclude=/proc \
  --exclude=/sys \
  --exclude=/tmp \
  --exclude=/run \
  --exclude=/mnt \
  --exclude=/media \
  --exclude=/lost+found \
  --exclude='home/*/.cache' \
  --exclude='home/*/.local/share/Trash' \
  --exclude='home/*/.gvfs' \
  -C / \
  etc boot home var/www usr/local \
  -C "$TEMP_DIR" package-list.txt

# Verify archive integrity
log_message "VERIFYING: Running post-backup archive integrity test..."
if tar -tzf "$ARCHIVE" > /dev/null 2>&1; then
  log_message "SUCCESS: Archive verification passed ($ARCHIVE)."
else
  log_message "FAILURE: Archive verification failed! Removing corrupted file ($ARCHIVE)."
  rm -f "$ARCHIVE"
  exit 1
fi

# Clean up archives older than 30 days
find "$BACKUP_PATH" -maxdepth 1 -name "raspi_backup_*.tar.gz" -mtime +30 -exec rm -f {} +

log_message "END: Backup process finished successfully."

3. Set Execution Permissions

Make the script executable:

chmod +x ~/scripts/raspi_backup.sh

Part 2: Schedule the Backup with Cron

Run the backup as root to preserve full system file ownerships:

sudo crontab -e

Add the entry below to run the script every Sunday at 2:00 AM.

Note: The cron output is explicitly piped to /dev/null because the script handles its own logging internally. Redirecting cron output prevents duplicate entries in raspi_backup.log.

0 2 * * 0 /home/pi/scripts/raspi_backup.sh > /dev/null 2>&1

Log outputs will appear in ~/scripts/raspi_backup.log:

2026-08-30 02:00:00 - START: Beginning system backup to /mnt/external_disk/raspi_backups/raspi_backup_2026-08-30.tar.gz
2026-08-30 02:02:15 - VERIFYING: Running post-backup archive integrity test...
2026-08-30 02:03:10 - SUCCESS: Archive verification passed (/mnt/external_disk/raspi_backups/raspi_backup_2026-08-30.tar.gz).
2026-08-30 02:03:10 - END: Backup process finished successfully.

Part 3: Restoring to a Fresh Raspbian Install

Follow these steps to restore your configurations, user files, and installed software onto a fresh installation.

1. Test Archive Integrity: Verify file integrity before extraction. Mount your external drive on the fresh OS install. Test the target archive to ensure it is valid before extracting:

tar -tzf /mnt/external_disk/raspi_backups/raspi_backup_2026-08-30.tar.gz > /dev/null

(If this completes silently without errors, your archive is healthy.)

2. Extract System Files: Unpack system directories to root. Extract the contents of the archive directly into root (/):

sudo tar -xzpf /mnt/external_disk/raspi_backups/raspi_backup_2026-08-30.tar.gz -C /

3. Reinstall Packages: Match previously installed packages. Reinstall all software recorded in the package selection file:

sudo dpkg --clear-selections
sudo dpkg --set-selections < /package-list.txt
sudo apt-get dselect-upgrade -y
sudo rm /package-list.txt

4. Reboot System: Apply configuration changes. Reboot to apply network settings, system configuration, and service states:

sudo reboot