Docker does not respect hosts file

[fooker]

The static docker binary uses the DNS server specified /etc/resolv.conf without consulting /etc/hosts beforehand. The image should contain a /etc/nsswitch.conf containing some minimal configuration which is used by the docker binary.

[tianon]

I believe this is a duplicate of #40.

[fooker]

Not sure. If I add the nsswitch.conf with some minimal content like below, it starts working.

hosts: files dns

[fooker]

After reading this again, I don't think this is a strict duplicate. Wether or not the native go dns implementation is used or not, in both cases, a nsswitch.conf should be provided. The native go implementation also supports a limited version of the file and must be configured to respect /etc/hosts (see https://github.com/golang/go/blob/4bd95702dd1e81f383ee67c14945620d30247908/src/net/conf.go#L198).

[tianon]

Huh, good point -- thinking/looking at it more, I think I like this solution better than that one, since it's adding a general config for DNS lookups rather than a debugging environment variable specifically to try and control Go's behavior (and in a way that's contrary to how upstream intentionally compiled said binary).

Looking a little further down in that same file at https://github.com/golang/go/blob/4bd95702dd1e81f383ee67c14945620d30247908/src/net/conf.go#L219-L253, it appears the only things supported by the netgo implementation are myhostname, files, dns, and mdns* (and then only *.local).

Looking at Debian's default file, it's got hosts: files dns, so I think that's probably what we ought to stick with (perhaps linking to all these resources from a comment). I'll work up a PR and have something ready to look at/test shortly. 👍

[tianon]

#84 👍