Note that this has taken down DNS on our firewall (and hence our network) a couple of times now, both annoyingly early in the morning when nobody was in to fix it.

can you share your DHCP configuration with us for reproducibility?

In addition can you disable the dhcp hostfile-update by removing it from your cofiguration?

> show service dhcp-server 
hostfile-update
shared-network-name VLAN101 
  subnet 172.16.101.0/24 {
    default-router 172.16.101.254
    dns-server 172.16.101.254
    domain-name guest.example.org
    lease 3600
    range 0 {
        start 172.16.101.1
        stop 172.16.101.250
    }
  }
}

We can't really disable hostfile-update, as we heavily use internal DNS records for development hardware.

Maybe if hostname is empty, we can prepend the mac address to the fqdn which will be stored in /etc/hosts

@thinkl33t can you please also provide a "faulty" /etc/hosts file?

The line giving the error is:

172.16.101.192 .guest.example.org #on-dhcp-event b4:e6:2a:54:a:ef

pdns-recursor will initially continue to run fine, but anything that forces it to restart or reload will cause it to fail to start.

can you edit /usr/libexec/vyos/system/on-dhcp-event.sh

and add this after changes=0

if [ -z "$client_name" ]; then
    logger -s -t on-dhcp-event "Client name was empty, using MAC \"$client_mac\" instead"
    client_name=$(echo "client-"$client_mac | tr : -)
fi

Brill, i've applied that patch and will keep an eye on it for a few days to see what happens.

Which log should i be monitoring to see the log output from that script?

/var/log/messages

Added the above snipped to vyos-1x and the latest rolling releases

@thinkl33t any updates?

We've not had this issue since i applied the patch.

I'm not sure if that is because the patch fixed it, or it wouldn't have
triggered anyway, but i can't see anything in the logs.

okay - then I kindly close this one.

Please reopen if it appears again.