Bug#923082: can't disable systemd-resolved

[Martin Pitt]

Control: tag -1 moreinfo

Hello Toni,

Toni [2019-02-23 23:05 +0000]:
> I can't disable systemd-resolved, which prevents me from running my own
> DNS setup:

systemd-resolved.service is not enabled by default in Debian. If you enabled
it, what prevents you from disabling it again? (systemctl disable
systemd-resolved).

> # systemctl disable --now systemd-resolved.service
> # lsof -i udp at 0.0.0.0:53                          
> COMMAND   PID   USER   FD   TYPE  DEVICE SIZE/OFF NODE NAME
> systemd     1   root  177u  IPv4   10583      0t0  UDP localhost:domain 
> dnsmasq 13861 nobody    5u  IPv4 5159825      0t0  UDP 192.168.122.1:domain 
> #
> 
> Since it runs inside PID 1, I cannot even kill it.

resolved doesn't run in pid 1 (that would be a really bad architecture!). This
just means that pid 1 connected to localhost's name server to resolve a name
(i. e. a DNS client). A better command to find out which processes are
*listening* on UDP ports is "ss -ulpen", or for port 53 specifically,
"ss -ulpen 'sport = 53'".

Martin