"Could not resolve hostname" on Pi for local services

Question

My Pi cannot resolve hostnames of other services in the same local network. Resolution of external services works fine.

$ nslookup example.com
Server:     127.0.0.1
Address:    127.0.0.1#53

Non-authoritative answer:
Name:   example.com
Address: 93.184.216.34
Name:   example.com
Address: 2606:2800:220:1:248:1893:25c8:1946

For example there's a host thesource.local that I connect to from my e.g. MacBook but name resolution from the Pi fails:

$ avahi-browse -a|grep SSH
+   eth0 IPv6 thesource                                     SSH Remote Terminal  local
+   eth0 IPv4 thesource                                     SSH Remote Terminal  local
$ ssh [email protected]
ssh: Could not resolve hostname thesource.local: Name or service not known

This is strictly an issue with local names on the Pi. Connecting from other hosts (e.g. the MacBook) to the Pi using ssh [email protected] works just fine (thanks to Bonjour/Avahi I guess).

My /etc/dhcpcd.conf looks like so as I need a static IP address:

interface eth0
static ip_address=192.168.0.10/24
static ip6_address=fd51:42f8:caae:d92e::ff/64
static routers=192.168.0.1
static domain_name_servers=192.168.0.1 9.9.9.9 2620:fe::fe

For the sake of completeness here's the (abbreviated) ipconfig output:

eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.0.10  netmask 255.255.255.0  broadcast 192.168.0.255
        inet6 fe80::8aa2:f238:cae7:82f3  prefixlen 64  scopeid 0x20<link>
        ether dc:a6:32:0f:cd:a4  txqueuelen 1000  (Ethernet)

Update 2020-03-29

More information asked for in the comments:

$ grep -v "#" /etc/avahi/avahi-daemon.conf|grep -v "\["

use-ipv4=yes
use-ipv6=yes
ratelimit-interval-usec=1000000
ratelimit-burst=1000

enable-wide-area=yes

publish-hinfo=no
publish-workstation=no

$ service avahi-daemon status
● avahi-daemon.service - Avahi mDNS/DNS-SD Stack
   Loaded: loaded (/lib/systemd/system/avahi-daemon.service; enabled; vendor preset: enabled)
   Active: active (running) since Sat 2020-03-28 19:46:11 CET; 17h ago
 Main PID: 329 (avahi-daemon)
   Status: "avahi-daemon 0.7 starting up."
    Tasks: 2 (limit: 4616)
   Memory: 1.2M
   CGroup: /system.slice/avahi-daemon.service
           ├─329 avahi-daemon: running [white-rose.local]
           └─340 avahi-daemon: chroot helper

Answer 1

I ran into the same issue when I did a clean buster install on a new sd card. It took a bit of digging, but found the readme.md in the nss-mDns GitHub repository wants to include mdns4 on the hosts line of /etc/nsswitch.conf:

hosts: files mdns4_minimal [NOTFOUND=return] dns mdns4

Since other hosts on the network could resolve the new Pi, <f>.local, I assumed it's mDns was properly broadcasting. In my case, running avahi-resolve -n <g>.local on <f> would find the address, but ping <g>.local would not; so it pointed me to how names were resolving.

It was hard to find because my working pi, <b>.local and the old image on the sd card I swapped out <g>.local didn't have that in nsswitch.conf. But, <b> is running Jessie; and I think <g> is running Stretch(?).