What’s the safest way to shorten hardware serial numbers for hostnames?

An asset tag is usually a better naming source than the manufacturer serial number. It can be kept within the hostname limit, works across Dell, HP, Lenovo, and Microsoft hardware, and makes it easier to match the computer to your asset register. You can still store the full serial number in your management or inventory system.

I’d avoid cutting the serial number unless you have a guaranteed uniqueness check. A serial is meant to identify the device as a whole, and the position of the characters may not carry a consistent meaning across models. If you must shorten it, generate the hostname from a controlled inventory system and verify that the shortened value is unique.

If the naming policy allows it, use the full serial number and change the policy instead of modifying the identifier. Otherwise, consider a short site or device prefix plus a generated unique ID, while retaining the complete serial number as a separate inventory attribute.

For Dell systems, the seven-character service tag is commonly used because it is short and designed to identify the device. For the other vendors, I would not assume that the first or last characters of a serial number can safely be discarded; check for collisions against your existing inventory whenever a shortened naming scheme is used.

A MAC address is available on most networked devices and can provide a common format, but it is not ideal as the primary identity because adapters can be replaced, devices can have multiple addresses, and wireless MAC randomization may be enabled. It’s better as a secondary identifier than as the hostname.