backup_script.sh

#!/bin/bash

# List of hosts to back up, including the local device (e.g., rpi5-1.example.com).
# Example: Add your Raspberry Pi hostnames or IPs.
REMOTES=("pi1-hostname" "pi2-hostname" "pi3-ip-address"

# Folders to back up from each host (space-separated).
# Example: Add more paths like "/home/$USER/config/" if needed.
FOLDERS_TO_BACKUP="/home/$USER/docker/ /var/lib/docker/volumes/"

# Central backup destination root.
# Example: Change to "/mnt/external/backup" for an external drive.
BACKUP_ROOT="/home/$USER/backup"

# SSH private key for remote hosts.
# Example: Use "/home/$USER/.ssh/id_ed25519" if using Ed25519 key.
SSH_KEY="/home/$USER/.ssh/id_rsa"

# Webhook URL for alerts, using Signal CLI REST API by default.
# Example: "http://localhost:8080/v2/send" for local Signal API or "https://discord.com/api/webhooks/..." for Discord.
WEBHOOK_URL="https://your-webhook-url.com/alert"

# Webhook recipient details for Signal alerts.
# Example: Add more numbers like "[\"+27123456789\", \"+12345678901\"]".
WEBHOOK_NUMBER="+27123456789"
WEBHOOK_RECIPIENTS="[\"+27123456789\"]"

# Get the local hostname (e.g., "rpi5-1.example.com") to detect local device.
LOCAL_HOST=$(hostname -f)

# Function to back up a single host (local or remote).
backup_host() {
    local host="$1"
    local subfolder="$BACKUP_ROOT/$host"
    
    # Create backup subfolder for this host (e.g., /home/$USER/backup/rpi5-1.example.com).
    mkdir -p "$subfolder"
    
    # Process each folder to back up.
    for folder in $FOLDERS_TO_BACKUP; do
        # Extract the last component of the folder path (e.g., "docker" or "volumes").
        folder_name=$(basename "$folder")
        
        # Check if the source folder exists on the host.
        if [ "$host" = "$LOCAL_HOST" ]; then
            # Local host: Use direct filesystem access.
            # Use sudo for /var/lib/docker/volumes/ as it requires root access.
            if [[ "$folder" == "/var/lib/docker/volumes/" ]]; then
                sudo -n test -d "$folder" 2>/dev/null
            else
                test -d "$folder" 2>/dev/null
            fi
        else
            # Remote host: Use SSH with sudo to check directory.
            ssh -i "$SSH_KEY" your_user@"$host" "sudo -n test -d $folder" 2>/dev/null
        fi
        if [ $? -ne 0 ]; then
            # If folder doesn't exist, send webhook alert and skip.
            curl -X POST -H "Content-Type: application/json" \
                 -d "{\"message\": \"Backup skipped for $host: directory $folder does not exist at $(date)\", \"number\": \"$WEBHOOK_NUMBER\", \"recipients\": $WEBHOOK_RECIPIENTS}" \
                 "$WEBHOOK_URL"
            echo "Skipping $host:$folder (directory does not exist)" >&2
            continue
        fi
        
        # Perform rsync backup.
        if [ "$host" = "$LOCAL_HOST" ]; then
            # Local host: Direct rsync, with sudo for /var/lib/docker/volumes/.
            if [[ "$folder" == "/var/lib/docker/volumes/" ]]; then
                sudo -n rsync -avz -P "$folder" "$subfolder/$folder_name/" 2>&1
            else
                rsync -avz -P "$folder" "$subfolder/$folder_name/" 2>&1
            fi
        else
            # Remote host: Rsync over SSH with sudo.
            # -a: Preserve permissions/timestamps, -v: Verbose, -z: Compress, -P: Progress and partial transfers.
            rsync -avz -P -e "ssh -i $SSH_KEY" --rsync-path="sudo -n rsync" your_user@"$host":"$folder" "$subfolder/$folder_name/" 2>&1
        fi
        if [ $? -ne 0 ]; then
            # If rsync fails, send webhook alert and log error.
            curl -X POST -H "Content-Type: application/json" \
                 -d "{\"message\": \"Backup failed for $host: rsync error on $folder at $(date)\", \"number\": \"$WEBHOOK_NUMBER\", \"recipients\": $WEBHOOK_RECIPIENTS}" \
                 "$WEBHOOK_URL"
            echo "Error backing up $host:$folder" >&2
            return 1
        fi
        
        # Create .last_backup file to track last successful backup time.
        touch "$subfolder/$folder_name/.last_backup"
    done
    
    # Log success and send webhook alert.
    echo "Backup completed for $host"
    curl -X POST -H "Content-Type: application/json" \
         -d "{\"message\": \"Backup completed for $host at $(date)\", \"number\": \"$WEBHOOK_NUMBER\", \"recipients\": $WEBHOOK_RECIPIENTS}" \
         "$WEBHOOK_URL"
    return 0
}

# Main loop: Back up all hosts in REMOTES array.
for host in "${REMOTES[@]}"; do
    backup_host "$host"
done