CentOS - Sep 2021 - 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?

--On Sunday, September 19, 2021 2:10 AM +0200 hw <hw at gc-24.de> wrote:
> 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?
Good question. I'm trying to do the same for my OpenWRT router to force my 
ISP to give me a new allocation. (It's stuck on a /64 and a Reddit thread 
suggests that changing the DUID will "kick" the DHCPv6 server into
honoring
my /60 request.) The DUID does the same for IPv6 that the MAC address does 
for IPv4. It's the key for the lease in the DHCP database.

I'm reading that DUIDs can get recomputed when containers are started, and 
this causes headaches for VM operators who are seeing "new"
assignments
appear extremely frequently.

--On Sunday, September 19, 2021 2:10 AM +0200 hw <hw at gc-24.de> wrote:
> So how/where do find I this DUID on my server?
<https://redhatlinux.guru/2019/07/01/find-duid-on-rhel-and-centos-servers/>

<https://askubuntu.com/questions/712159/how-can-i-find-out-my-systems-dhcpv6-duid>

My desktop has it in /var/lib/NetworkManager. I haven't yet figured out 
what generates it or how it gets set on a server, as my servers don't have 
one (that I can find). My suspicion is that it gets generated from the UUID 
setting for the interface in /etc/sysconfig/network-scripts/ifcfg-*.