Automated Backup Script with Rotation

Intermediate15 min

Create a bash script that performs timestamped backups of files and directories with configurable retention and automatic rotation of old backups.

Prerequisites

-Bash 4.0+
-tar and gzip installed
-Write access to backup destination

Steps

Create the backup script

Write a script that creates timestamped compressed backups of a source directory.

$ cat > backup.sh << 'EOF' #!/usr/bin/env bash set -euo pipefail SOURCE_DIR="${1:?'Usage: backup.sh <source> <dest> [retention_days]'}" BACKUP_DIR="${2:?'Usage: backup.sh <source> <dest> [retention_days]'}" RETENTION_DAYS="${3:-30}" TIMESTAMP=$(date +'%Y%m%d_%H%M%S') BACKUP_NAME="backup_${TIMESTAMP}.tar.gz" mkdir -p "$BACKUP_DIR" tar -czf "$BACKUP_DIR/$BACKUP_NAME" -C "$(dirname "$SOURCE_DIR")" "$(basename "$SOURCE_DIR")" echo "Backup created: $BACKUP_DIR/$BACKUP_NAME" EOF chmod +x backup.sh

Add backup rotation

Delete backups older than the retention period to prevent disk space exhaustion.

$ cat >> backup.sh << 'EOF' # Rotate old backups DELETED=$(find "$BACKUP_DIR" -name 'backup_*.tar.gz' -mtime +"$RETENTION_DAYS" -print -delete | wc -l) echo "Rotated $DELETED backups older than $RETENTION_DAYS days" EOF

Always test the find -delete command with -print first to verify which files would be removed before adding -delete.

Add backup verification

Verify the backup archive is valid and not corrupted after creation.

$ echo 'tar -tzf "$BACKUP_DIR/$BACKUP_NAME" > /dev/null && echo "Backup verified successfully" || { echo "Backup verification FAILED" >&2; exit 1; }' >> backup.sh

Schedule with cron

Add a cron job to run the backup daily at 2 AM.

$ (crontab -l 2>/dev/null; echo '0 2 * * * /path/to/backup.sh /data /backups 30 >> /var/log/backup.log 2>&1') | crontab -

Use >> to append to the log file and 2>&1 to capture both stdout and stderr.

Full Script

full-script.sh

#!/usr/bin/env bash
set -euo pipefail

# Automated Backup with Rotation
SOURCE_DIR="${1:?'Usage: backup.sh <source> <dest> [retention_days]'}"
BACKUP_DIR="${2:?'Usage: backup.sh <source> <dest> [retention_days]'}"
RETENTION_DAYS="${3:-30}"
TIMESTAMP=$(date +'%Y%m%d_%H%M%S')
BACKUP_NAME="backup_${TIMESTAMP}.tar.gz"

log() { echo "[$(date +'%Y-%m-%d %H:%M:%S')] $*"; }

# Validate source
[[ ! -d "$SOURCE_DIR" ]] && { echo "Source not found: $SOURCE_DIR" >&2; exit 1; }

# Create backup directory
mkdir -p "$BACKUP_DIR"

# Create backup
log "Backing up $SOURCE_DIR -> $BACKUP_DIR/$BACKUP_NAME"
tar -czf "$BACKUP_DIR/$BACKUP_NAME" -C "$(dirname "$SOURCE_DIR")" "$(basename "$SOURCE_DIR")"

# Get size
SIZE=$(du -h "$BACKUP_DIR/$BACKUP_NAME" | cut -f1)
log "Backup size: $SIZE"

# Verify
tar -tzf "$BACKUP_DIR/$BACKUP_NAME" > /dev/null
log "Backup verified successfully"

# Rotate old backups
DELETED=$(find "$BACKUP_DIR" -name 'backup_*.tar.gz' -mtime +"$RETENTION_DAYS" -print -delete | wc -l)
log "Rotated $DELETED old backups (retention: $RETENTION_DAYS days)"

# Summary
TOTAL=$(find "$BACKUP_DIR" -name 'backup_*.tar.gz' | wc -l)
log "Total backups: $TOTAL"

FAQ

Discussion

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#!/usr/bin/env bash set -euo pipefail # Automated Backup with Rotation SOURCE_DIR="${1:?'Usage: backup.sh <source> <dest> [retention_days]'}" BACKUP_DIR="${2:?'Usage: backup.sh <source> <dest> [retention_days]'}" RETENTION_DAYS="${3:-30}" TIMESTAMP=$(date +'%Y%m%d_%H%M%S') BACKUP_NAME="backup_${TIMESTAMP}.tar.gz" log() { echo "[$(date +'%Y-%m-%d %H:%M:%S')] $*"; } # Validate source [[ ! -d "$SOURCE_DIR" ]] && { echo "Source not found: $SOURCE_DIR" >&2; exit 1; } # Create backup directory mkdir -p "$BACKUP_DIR" # Create backup log "Backing up $SOURCE_DIR -> $BACKUP_DIR/$BACKUP_NAME" tar -czf "$BACKUP_DIR/$BACKUP_NAME" -C "$(dirname "$SOURCE_DIR")" "$(basename "$SOURCE_DIR")" # Get size SIZE=$(du -h "$BACKUP_DIR/$BACKUP_NAME" | cut -f1) log "Backup size: $SIZE" # Verify tar -tzf "$BACKUP_DIR/$BACKUP_NAME" > /dev/null log "Backup verified successfully" # Rotate old backups DELETED=$(find "$BACKUP_DIR" -name 'backup_*.tar.gz' -mtime +"$RETENTION_DAYS" -print -delete | wc -l) log "Rotated $DELETED old backups (retention: $RETENTION_DAYS days)" # Summary TOTAL=$(find "$BACKUP_DIR" -name 'backup_*.tar.gz' | wc -l) log "Total backups: $TOTAL"