Ubuntu and .local hostnames in a corporate network

In the past, I’ve had trouble getting my Ubuntu machine to resolve the .local hostnames at work. I didn’t know why Ubuntu had this problem while other machines did not.

When I did a DNS lookup, it failed, and ping of host.something.local failed. Yet ping of the hostname without the .something.local extension worked. Odd. I googled various terms, but nothing useful came up. I tried watching the DNS lookup with tcpdump, but it didn’t capture anything.

Eventually, I thought of using ‘strace ping host.something.local’ to see what was happening, and it turns out that DNS was never being queried — it was talking to something called avahi.

I googled “avahi”, and was reminded that hostname resolution is configured in /etc/nsswitch.conf. In the case of Ubuntu, it’s configured to send *.local requests to Avahi (mdns4_minimal), and no further — i.e. if Avahi doesn’t resolve it, it doesn’t try DNS.

In my case, I want corporate DNS to resolve .local addresses. So I changed my /etc/nsswitch.conf from this:

hosts: files mdns4_minimal [NOTFOUND=return] wins dns mdns4

to this:

hosts: files wins dns mdns4_minimal mdns4

And now my Ubuntu development machine can communicate with our internal .local machines without having to resort to using IP addresses, short names, or having to place the mapping in /etc/hosts.