Improve robustness by adding input validation and sanitization. Replace SIGINT/SIGTERM trap payloads with numeric exit codes (130 and 143). Sanitize hostname to allowed characters and notify the user if it was adjusted. Add validation loops and user messages for CPU cores and RAM (positive integers), MAC address format (XX:XX:XX:XX:XX:XX), VLAN (1-4094 or default), and MTU (576-65520 or default). Minor output ordering tweaks to ensure values are echoed after processing.
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