Simple rotation backup script

backup.sh

#!/bin/bash

#
# backup.sh – Simple rotation backup script
#
# Creates a compressed archive of SOURCE into TARGET with a timestamp,
# and keeps only the most recent MAX_BACKUPS archives.
#
# Requirements: Bash 4+, cron

# -------------------- Configuration --------------------
# Path to the directory or file to be backed up
SOURCE="/path/to/source"
# Path where backup archives will be stored
TARGET="/path/to/backup"

# Prefix for backup archive filenames
PREFIX="backup"

# Maximum number of backup archives to keep (older ones are removed)
MAX_BACKUPS=10

# -------------------- Main script --------------------
# Create TARGET if it doesn't exist (with parent directories)
mkdir -p "$TARGET"

# Timestamp in YYYYMMDD_HHMM format
DATETIME=$(date +"%Y%m%d_%H%M")

# Full path of the new archive
BACKUP_FILE="$TARGET/${PREFIX}_${DATETIME}.tar.gz"

# Create compressed tarball:
# -C changes to SOURCE's parent, so the archive contains only the basename
tar -czf "$BACKUP_FILE" -C "$(dirname "$SOURCE")" "$(basename "$SOURCE")"

# List existing archives, sorted newest-first (ls -1t)
mapfile -t FILES < <(ls -1t "$TARGET"/${PREFIX}_*.tar.gz 2>/dev/null)

# If we have more than MAX_BACKUPS, delete the oldest ones
if [ ${#FILES[@]} -gt $MAX_BACKUPS ]; then
    # The array is sorted newest → oldest.
    # The oldest are at indices MAX_BACKUPS .. end.
    # Delete all files from index MAX_BACKUPS onward.
    for ((i=MAX_BACKUPS; i<${#FILES[@]}; i++)); do
        rm -f "${FILES[$i]}"
    done
fi

# -------------------- End of script --------------------