DNS info is not loaded by dhclient

[Pengpeng Sun]

Hi Team,

Could you please help to confirm if this is an issue on Ubuntu19.10 Desktop?

1. Update /etc/dhcp/dhclient.conf file to include below 2 new lines.
   supersede domain-name "vmware.com";
   supersede domain-name-servers 10.117.0.1;

2. Reboot

3. check DNS info by "systemd-resolve --status", the DNS domain and server is not set. But /run/systemd/resolved.conf.d/isc-dhcp-v4-ens160.conf contains the new DNS domain and server.

4. Manually run "systemctl try-reload-or-restart systemd-resolved.service" and then DNS is set correctly, "systemd-resolve --status" output have the new DNS domain and server.

I tried the same steps on Ubuntu18.04 Desktop, no such issue. DNS updated correctly after reboot.

Thanks,
Pengpeng

[Till Kamppeter (till-kamppeter)]

Looks like that during boot time components get fired up in wrong order, some dependency in the systemd service files is needed.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Pengpeng Sun (pengpengs)]

Thanks Till, which systemd service's dependency got changed?

I compared /lib/systemd/system/systemd-resolved.conf between 18.04 and 19.10, they are same. There is "After=systemd-sysusers.service systemd-networkd.service".

I do NOT know when and who triggers /etc/dhcp/dhclient-enter-hooks.d/resolved script at boot, but it's possible that when this script executed, systemd-resolved.service is not ready for reload or restart.

[Dan Streetman (ddstreet)]

@pengpengs can you test with the systemd versions from this ppa:
https://launchpad.net/~ddstreet/+archive/ubuntu/systemd

I suspect this might be caused by bug 1849608

[Pengpeng Sun (pengpengs)]

Thanks @Dan, I applied the patch https://launchpadlibrarian.net/448207988/resolved.patch to my VM, but the issue is still reproducing.
The md5sum line is before creating "$statedir/isc-dhcp-v4-$interface.conf", while I can see the isc-dhcp-v4-$interface.conf file is created on my VM.

I think the root cause is not same with bug 1849608

[Pengpeng Sun (pengpengs)]

@Dan, The issue is resolved by your fix.

Instead of only changing /etc/dhcp/dhclient-enter-hooks.d/resolved script, I added your repository "ppa:ddstreet/systemd" and updated/upgraded systemd, then the issue was NOT reproducing.

[Pengpeng Sun (pengpengs)]

@Dan, could you please confirm if your fix will be patched on Ubuntu19.10? If yes, when it will happen?

[Balint Reczey (rbalint)]

@pengpengs The fix is present in the systemd version in eoan-proposed and will be released around next week when all the all the fixes are verified.

https://launchpad.net/ubuntu/+source/systemd/242-7ubuntu3.2

[Pengpeng Sun (pengpengs)]

@Balint, thanks a lot for the information.

[vmware-gos-Yuhua (yhzou)]

DNS setting is correct with updated systemd package 242-7ubuntu3 from -proposed.

[Dan Streetman (ddstreet)]

please reopen if this is still an issue