Not resolving using search domain

[NoumanSaleem]

Hostname is not properly resolving within the container when setting --dns-search on Docker.

Docker settings:

DOCKER_OPTS="--bip=172.17.42.1/16 --dns=172.17.42.1 --dns=10.0.2.15 --dns-search=service.consul"

gliderlabs/alpine

vagrant@local:~$ docker run --rm -it gliderlabs/alpine sh
/ # ping consul
ping: bad address 'consul'
/ # ping consul.service.consul
PING consul.service.consul (10.211.55.22): 56 data bytes
64 bytes from 10.211.55.22: seq=0 ttl=64 time=0.045 ms

progrium/busybox

vagrant@local:~$ docker run --rm -it progrium/busybox
/ # ping consul
PING consul (10.211.55.22): 56 data bytes

gliderlabs/registrator#111

[andyshinn]

Looks like musl doesn't support domain and search in resolv.conf: http://wiki.musl-libc.org/wiki/Functional_differences_from_glibc#Name_Resolver_.2F_DNS. We're researching workarounds to this issue. Thanks for reporting!

[brycekahle]

@andyshinn the musl behavior of querying all nameservers in /etc/resolv.conf in parallel and using the the first response is unexpected. Perhaps that could be added to the documentation?

[andyshinn]

Yep, agree it should be noted somewhere. I'll add some more information to the docs about the caveats soon.

[pikeas]

@andyshinn The docs are a good start, but they raise further questions. It would be great if the section on dnsmasq (http://gliderlabs.viewdocs.io/docker-alpine/caveats) could be fleshed out to provide a full solution.

[andyshinn]

I tried to provide a general example of the use case where you want to send internal requests to a Consul server and the rest out to upstream name servers. What specifically do you think the example is missing?

[pikeas]

A brief description of dnsmasq and how to use it - on the host, as an additional container, etc. In other words, specific instructions on use, rather than "maybe try this workaround".

[progrium]

I think it could use a full dnsmasq config for the custom+upstream DNS
scenario so people can figure out how to run it on the host, then a pointer
to a good generic dnsmasq Docker container that would be easy to apply that
configuration for people that want to run it in a container, and lastly,
once available, a pointer to our magic resolve container.

On Tue, Mar 24, 2015 at 3:36 PM, Aris Pikeas notifications@github.com
wrote:

A brief description of dnsmasq and how to use it - on the host, as an
additional container, etc. In other words, specific instructions on use,
rather than "maybe try this workaround".

—
Reply to this email directly or view it on GitHub
#8 (comment)
.

Jeff Lindsay
http://progrium.com

[thockin]

I was so hopeful for docker-alpine - I need a mini package for DNS utils. Alas, DNS in alpine seems to be totally busted. A shame.

[tifayuki]

I set up a dnsmasq container. In resolv.dnsmasq.conf, I added

nameserver 8.8.8.8
search example.com

In alpine container I set the dns pointing to that dnsmasq container.

The problem is when I do ping base in alpine container, the log of dnsmasq shows that only base is sent to 8.8.8.8, but base.example.com is never queried.

[andyshinn]

The 3 dnsmasq options that might append a domain to unqualified names is --expand-hosts, --domain, and --auth-zone. Can you try setting these to see if it changes the behavior? Unfortunately, the only other way to do this is with some host file manipulation on the dnsmasq container.

[neilellis]

This cannot be solved using dnsmasq, dnsmasq assumes glibc has expanded the hostname from the search entry in /etc/resolv.conf.

If you are in an environment (like Tutum) where links don't work because of this:

https://gist.github.com/neilellis/8983d6977f45f126df28

Is my workaround in conjunction with running dnsmasq:

dnsmasq --resolv-file=/etc/dnsmasq-resolv.conf --addn-hosts=/etc/hosts.links --no-daemon

The full image is at https://github.com/vizzbuzz/base-alpine