feat: add mysql backup script

docs/linux/mysql-backup.md

@@ -0,0 +1,90 @@
+# Script
+
+```bash
+#!/bin/bash
+
+# usage: ./mysql_backup.sh <username> <password> <database_name>
+if [ $# -ne 3 ]; then
+  echo "Error: Missing required parameters"
+  echo "Usage: $0 <username> <password> <database_name>"
+  exit 1
+fi
+
+# configuration
+MYSQL_HOST="<ip_address>"
+MYSQL_PORT="3306"
+MYSQL_USER="$1"
+MYSQL_PASS="$2"
+DATABASE_NAME="$3"
+BACKUP_DIR="/mnt/backup"
+BACKUP_FILE="$BACKUP_DIR/pms.sql"
+TEMP_BACKUP_FILE="$BACKUP_DIR/backup_temp.sql"
+
+# check if backup directory exists
+if [ ! -d "$BACKUP_DIR" ]; then
+  echo "Error: Backup directory $BACKUP_DIR does not exist"
+  exit 1
+fi
+
+# check if backup directory is writable
+if [ ! -w "$BACKUP_DIR" ]; then
+  echo "Error: Backup directory $BACKUP_DIR is not writable"
+  exit 1
+fi
+
+# test mysql connection before proceeding
+mysql -h "$MYSQL_HOST" -P "$MYSQL_PORT" -u "$MYSQL_USER" -p"$MYSQL_PASS" -e "SELECT 1;" "$DATABASE_NAME" >/dev/null 2>&1
+if [ $? -ne 0 ]; then
+  echo "Error: Cannot connect to MySQL database"
+  exit 1
+fi
+
+# Remove old backup file if it exists
+if [ -f "$BACKUP_FILE" ]; then
+  rm "$BACKUP_FILE"
+fi
+
+# perform database dump with optimized settings for minimal locking
+# --single-transaction: Uses consistent read for InnoDB tables
+# --routines:           Include stored procedures and functions
+# --triggers:           Include triggers
+# --lock-tables=false:  Don't lock tables (relies on single-transaction)
+# --quick:              Retrieve rows one at a time rather than buffering entire result set
+# --extended-insert:    Use multiple-row INSERT syntax for faster restores
+mysqldump \
+  -h "$MYSQL_HOST" \
+  -P "$MYSQL_PORT" \
+  -u "$MYSQL_USER" \
+  -p"$MYSQL_PASS" \
+  --single-transaction \
+  --routines \
+  --triggers \
+  --lock-tables=false \
+  --quick \
+  --extended-insert \
+  --no-tablespaces \
+  --default-character-set=utf8mb4 \
+  "$DATABASE_NAME" > "$TEMP_BACKUP_FILE"
+
+# check if mysqldump completed successfully
+if [ $? -eq 0 ] && [ -s "$TEMP_BACKUP_FILE" ]; then
+
+  # move temporary backup to final location
+  mv "$TEMP_BACKUP_FILE" "$BACKUP_FILE"
+
+  # return succesfull backup
+  echo "Backup completed successfully: $BACKUP_FILE"
+  echo "Backup size: $(du -h "$BACKUP_FILE" | cut -f1)"
+  exit 0
+else
+
+  # clean up temporary file on failure
+  if [ -f "$TEMP_BACKUP_FILE" ]; then
+    rm "$TEMP_BACKUP_FILE"
+  fi
+
+  # return failed backup
+  echo "Error: Database backup failed"
+  exit 1
+fi
+```