/etc/machine-id changes with every reboot

http://paste.ubuntu.com/23124588/ has an excerpt of my DHCP server log

... and i only used console-conf to configure the booted image ...

I cannot reproduce this; I'm using dnsmasq as a DNS server, not sure if that makes any difference -- but the networkd (via netplan) client sends the MAC and hostname, and dnsmasq always hands out the same IP for the same MAC/host name. Can you check the leases file of your DHCP server whether it actually stores MAC/hostname?

@pitti, well, it does so for all other devices relibaly ...

ogra@wall2:~$ ls -l /var/lib/dhcp/dhcpd.leases
-rw-r--r-- 1 root root 2076248 Sep 5 12:36 /var/lib/dhcp/dhcpd.leases

ogra@wall2:~$ grep DHC /var/log/syslog|tail -1
Sep 5 12:36:48 wall2 dhcpd: DHCPACK on 192.168.2.66 to 44:d9:e7:58:80:f9 (APOffice) via p4p1

i highly doubt it is in any way related to the server ...

http://paste.ubuntu.com/23136718/ has a grep for the MAC through the leases file ...

note that the device has not been rebooted since 2016/09/02 19:03:33 ... (line 2746 in above paste), it only gets a new IP on reboot

networkd sends a DUID (https://tools.ietf.org/html/rfc3315#section-9) composed of a constant vendor ID and /etc/machine-id. Does /etc/machine-id change in between reboots for you for some reason?

FTR, we can also set "ClientIdentifier=mac" in the .network config.

ogra@localhost:~$ cat /etc/machine-id
79a9b831ef0c46e1afbb3bbd00816461
ogra@localhost:~$ sudo reboot
Connection to 192.168.2.47 closed by remote host.
Connection to 192.168.2.47 closed.
...

i see the IP changed to 192.168.2.23 in teh serial console output ...

ogra@localhost:~$ cat /etc/machine-id
144a0d35563d419fa404d833641b6f51
ogra@localhost:~$

... and so did the machine-id ...

Ah, that explains it. IRC conversation suggests that /etc/machine-id is not part of the root file system but mounted from someplace else -- this must happen in the initramfs already, not during boot (that's too late).

so i added the necessary fixes to the ubuntu-core image, but there is still something wrong even with a non-moving machine-id ...

i have verified the id stays the same from first boot on, but the IP still changes once on second boot, but then stays the same for all subsequent ones ...

sadly on first boot console-conf runs and tells you which IP to use so you can not find the device if you actually try to use this IP after a reboot.

@Oliver: What is console-conf using to retrieve a IP address over DHCP? If it is dhclient and in a subsequent boot networkd is used then we have different storage locations for the leases which would explain why the DHCP request is sent again and a new IP address assigned.