Ubuntu 18.04 + Docker 17.12.1-ce break DNS resolution #2187
Description
This might be a dupe of #1654 (which is closed - but then this is still happening). /CC @sanimej who's been looking at that last year.
The default installation of Docker on Ubuntu 18.04 is broken if Google DNS servers 8.8.8.8 and 8.8.4.4 are not reachable for some reason.
Out of the box Ubuntu runs systemd, which creates a nameserver running on localhost:
$ docker --version
Docker version 17.12.1-ce, build 7390fc6
$ cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=18.04
DISTRIB_CODENAME=bionic
DISTRIB_DESCRIPTION="Ubuntu 18.04 LTS"
$ cat /etc/resolv.conf
# This file is managed by man:systemd-resolved(8). Do not edit.
# [...]
nameserver 127.0.0.53
Docker ignores the localhost nameserver:
$ docker run -ti busybox cat /etc/resolv.conf
# This file is managed by man:systemd-resolved(8). Do not edit.
# [...]
nameserver 8.8.8.8
nameserver 8.8.4.4
Because on my network, 8.8.8.8 is not reachable for some reason (different bug), name lookups time out:
$ docker run -ti busybox nslookup www.google.com
Server: 8.8.8.8
Address 1: 8.8.8.8
nslookup: can't resolve 'www.google.com'
For completeness sake, the symptom that lead me to find this is that when building a Go based image and running go get in a build step, I get a Could not resolve host: github.com (took me a while to piece this one together...):
Step 6/9 : RUN go get ./
---> Running in f64c6b120d88
# cd .; git clone https://github.com/julienschmidt/httprouter /go/src/github.com/julienschmidt/httprouter
Cloning into '/go/src/github.com/julienschmidt/httprouter'...
fatal: unable to access 'https://github.com/julienschmidt/httprouter/': Could not resolve host: github.com
package github.com/julienschmidt/httprouter: exit status 128