On Windows you can use ipconfig /all
to find the DUID & IAID:
Ethernet adapter VirtualBox Host-Only Network:
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : VirtualBox Host-Only Ethernet Adapter
Physical Address. . . . . . . . . : XX-XX-XX-XX-XX-XX
DHCP Enabled. . . . . . . . . . . : No
Autoconfiguration Enabled . . . . : Yes
Link-local IPv6 Address . . . . . : fe80::40d5:d138:125e:4478%21(Preferred)
IPv4 Address. . . . . . . . . . . : 192.168.56.1(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . :
DHCPv6 IAID . . . . . . . . . . . : 352845825
DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-16-E0-CE-11-50-E5-49-C8-14-AA
DNS Servers . . . . . . . . . . . : fec0:0:0:ffff::1%1
fec0:0:0:ffff::2%1
fec0:0:0:ffff::3%1
NetBIOS over Tcpip. . . . . . . . : Enabled
On Linux, its going to depend on your DHCPv6 client. By default, IPv6 does not use DHCP, so you need to enable it explicitly on all of your clients.
For example, by default, the wide DHCPv6 client stores the DUID in the file:
/var/lib/dhcpv6/dhcp6c_duid