Ubuntu 18.04: unbound seems to stop working after a period of time

[Jakob Habedank]

Hi all,

I set up pi-hole with unbound on my ubuntu 18.04 machine. I followed the
instructions by pi-hole[1].

Clients can reach websites with this method but after some time I get
timeouts. Pihole is still forwarding requests to 127.0.0.1 but it seems
that unbound doesn't answer anymore. Even on the host machine I get
timeouts.

    dig pi-hole.net @127.0.0.1 -p 5353

    ; <<>> DiG 9.11.3-1ubuntu1.8-Ubuntu <<>> pi-hole.net @127.0.0.1 -p 5353
    ;; global options: +cmd
    ;; connection timed out; no servers could be reached

Only `systemctl restart unbound` solves this problem. Unbound is still
running and doesn't show any obvious errors though.
I posted on the pi-hole forums and added quite some information there so
you might want to check the thread [2].

I'm quite new to Unix so please tell me what information you need to
help. Thanks!

[1] https://docs.pi-hole.net/guides/unbound/

[2]
https://discourse.pi-hole.net/t/pihole-on-ubuntu-18-04-with-unbound-fails-after-some-time/22585