Backup Scripts

Backup scripts are one of the most practical applications of bash scripting. Learn to create reliable, automated backup solutions.

Simple File Backup

Basic backup with timestamp:

#!/bin/bash

SOURCE="/home/user/documents"
DEST="/backup"
DATE=$(date +%Y%m%d_%H%M%S)

cp -r "$SOURCE" "$DEST/documents_$DATE"
echo "Backup completed: documents_$DATE"

Compressed Backup

Create compressed archives:

#!/bin/bash

SOURCE="$1"
BACKUP_DIR="/backup"
DATE=$(date +%Y%m%d)
ARCHIVE="$BACKUP_DIR/$(basename "$SOURCE")_$DATE.tar.gz"

# Create backup directory
mkdir -p "$BACKUP_DIR"

# Create compressed archive
tar -czf "$ARCHIVE" -C "$(dirname "$SOURCE")" "$(basename "$SOURCE")"

echo "Created: $ARCHIVE"
ls -lh "$ARCHIVE"

Exercise: Create Backup Function

Write a backup function:

Incremental Backups

Only backup changed files:

#!/bin/bash

SOURCE="/home/user/documents"
DEST="/backup/incremental"
LAST_BACKUP="$DEST/.last_backup"

mkdir -p "$DEST"

if [ -f "$LAST_BACKUP" ]; then
    # Backup only files newer than last backup
    find "$SOURCE" -newer "$LAST_BACKUP" -type f | while read -r file; do
        rel_path="${file#$SOURCE/}"
        mkdir -p "$DEST/$(dirname "$rel_path")"
        cp "$file" "$DEST/$rel_path"
        echo "Backed up: $rel_path"
    done
else
    # First backup - copy everything
    cp -r "$SOURCE"/* "$DEST/"
fi

# Update timestamp
touch "$LAST_BACKUP"

Rotation Strategy

Keep limited number of backups:

#!/bin/bash

BACKUP_DIR="/backup"
MAX_BACKUPS=7

# Create new backup
DATE=$(date +%Y%m%d_%H%M%S)
create_backup "$DATE"

# Remove old backups
cd "$BACKUP_DIR"
ls -t backup_*.tar.gz | tail -n +$((MAX_BACKUPS + 1)) | while read -r old; do
    echo "Removing old backup: $old"
    rm "$old"
done

Full Backup Script

Complete backup script with error handling:

#!/bin/bash
set -euo pipefail

# Configuration
SOURCE="${SOURCE:-/home/user/documents}"
DEST="${DEST:-/backup}"
MAX_BACKUPS="${MAX_BACKUPS:-7}"
LOG_FILE="/var/log/backup.log"

# Functions
log() {
    echo "[$(date '+%Y-%m-%d %H:%M:%S')] $*" | tee -a "$LOG_FILE"
}

die() {
    log "ERROR: $1"
    exit 1
}

cleanup_old_backups() {
    local count
    count=$(ls -1 "$DEST"/backup_*.tar.gz 2>/dev/null | wc -l)

    if [ "$count" -gt "$MAX_BACKUPS" ]; then
        ls -t "$DEST"/backup_*.tar.gz | tail -n +$((MAX_BACKUPS + 1)) | \
        while read -r old; do
            log "Removing: $old"
            rm "$old"
        done
    fi
}

# Main
log "Starting backup of $SOURCE"

# Validate
[ -d "$SOURCE" ] || die "Source not found: $SOURCE"
mkdir -p "$DEST" || die "Cannot create destination: $DEST"

# Create backup
DATE=$(date +%Y%m%d_%H%M%S)
ARCHIVE="$DEST/backup_$DATE.tar.gz"

if tar -czf "$ARCHIVE" -C "$(dirname "$SOURCE")" "$(basename "$SOURCE")"; then
    log "Created: $ARCHIVE ($(du -h "$ARCHIVE" | cut -f1))"
    cleanup_old_backups
    log "Backup completed successfully"
else
    die "Backup failed"
fi

Database Backup

Backup databases:

#!/bin/bash

DB_NAME="myapp"
BACKUP_DIR="/backup/db"
DATE=$(date +%Y%m%d)

mkdir -p "$BACKUP_DIR"

# PostgreSQL
pg_dump "$DB_NAME" | gzip > "$BACKUP_DIR/${DB_NAME}_$DATE.sql.gz"

# MySQL
mysqldump -u root -p"$DB_PASS" "$DB_NAME" | gzip > "$BACKUP_DIR/${DB_NAME}_$DATE.sql.gz"

# Verify
if [ -f "$BACKUP_DIR/${DB_NAME}_$DATE.sql.gz" ]; then
    echo "Database backup successful"
else
    echo "Database backup failed!" >&2
    exit 1
fi

Remote Backup

Backup to remote server:

#!/bin/bash

SOURCE="/home/user/documents"
REMOTE="backup@server.com:/backups/"
DATE=$(date +%Y%m%d)

# Using rsync (efficient, incremental)
rsync -avz --delete "$SOURCE" "$REMOTE/current/"

# Create dated snapshot
ssh backup@server.com "cp -al /backups/current /backups/backup_$DATE"

echo "Remote backup completed"

Exercise: Verify Backup

Check backup file exists:

Backup Best Practices

1. Test restores - Backups are useless if they can't be restored
2. Monitor backups - Log and alert on failures
3. Encrypt sensitive data - Use gpg for encryption
4. Off-site copies - Don't keep all backups in one place
5. Verify integrity - Check checksums
6. Document procedure - Write restore instructions

# Encrypt backup
tar -czf - "$SOURCE" | gpg -c > backup.tar.gz.gpg

# Verify with checksum
sha256sum backup.tar.gz > backup.tar.gz.sha256

# Later, verify integrity
sha256sum -c backup.tar.gz.sha256

Key Takeaways

• Use timestamps in backup filenames
• Compress backups with tar -czf
• Implement rotation to manage disk space
• Add error handling and logging
• Test restore procedures regularly
• Consider incremental backups for large data
• Use rsync for remote/network backups
• Encrypt sensitive backups