[CentOS] how to display/create DUID?

Hi,

I would like to assign an ipv6 address through the DHCPv6 server of pfsense. To configure a static address, I need to tell the DHCPv6 server a DUID.

Apparently DUIDs belong to a particular machine and aren't supposed to ever change unless you re-install the operating system. I guess every network card would need it's DUID because devices can have multiple network adapters, though ... and what happens when you change out the card?

IIUC, the DUID is required to ask for/get ipv6 addresses from a DHCPv6 server. So there must be a way to create one, and perhaps it has already been created. Does networkmanager do that?

So how/where do find I this DUID on my server?