BIOS and boot menus

When a machine powers on but won’t reach its operating system — or you’re reimaging it — the firmware setup screen still knows what the machine is. Every vendor puts the serial (and often the model) on the first page of BIOS setup.

The keys

Tap the key repeatedly, starting the moment you press power. Holding it down works better on some machines than tapping — both are noted below where the vendor says so.

If a key never seems to register, the machine is probably booting too fast to see it. Shut down completely (hold power 5 seconds), then start tapping the instant you press power again. On Windows, disabling Fast Startup also helps.

The route that always works on Windows

You don’t have to win the keypress race. From a booted Windows machine:

Settings → System → Recovery → Advanced startup → Restart now → Troubleshoot → Advanced options → UEFI Firmware Settings → Restart.

Or from an admin PowerShell, the same thing in one line:

shutdown /r /o /t 0

The same thing on Linux

On any systemd machine (all our Linux boxes):

systemctl reboot --firmware-setup

That reboots straight into firmware setup with no key-tapping.

Macs have no BIOS

• Apple Silicon (M-series): shut down, then press and hold the power button until “Loading startup options” appears. That’s the boot picker; Options gets you into Recovery.
• Intel Macs: hold Option at the chime for the boot picker, or Command-R for Recovery.
• To read the serial from Recovery, open Utilities → Terminal and run system_profiler SPHardwareDataType.

What the firmware screen tells you

On every brand above, the first page of setup shows some combination of:

• Serial number / Service Tag — this is the value for the inventory’s Serial field.
• Model or product name — the value for the Model field.
• Asset Tag — an editable field, blank on our machines. Leave it alone; our asset tag lives on the label, not in firmware.
• BIOS/UEFI version, CPU, and installed memory — worth noting when the asset record’s specs look wrong.

Read, don’t change. Boot order, Secure Boot, SATA mode, and TPM settings can leave a machine unbootable or an encrypted disk unopenable. If you only came for the serial, note it and press Esc to exit without saving.

Servers: read it without touching the machine

The PowerEdge has a service processor (iDRAC) with its own network port and web UI — its dashboard shows the service tag, model, and express service code without powering anything on or off. That’s the right way to identify a server that’s in use.