Docker for Mac doesn't read hosts /etc/hosts correctly when using aliases

[flxsource]

Expected behavior

Docker Engine is able to resolve the host name and any aliases declared in the /etc/hosts file on the host OS.

Actual behavior

Docker Engine is only able to resolve the host name, but not any aliases.

Information

Diagnostic ID: AF53934A-7F40-4AAA-82E7-6093DE58E779

We are running a Docker registry on our internal network, and a second registry configured as a pull through cache on the same machine, but under a different hostname. The two hostnames used are currently NOT in DNS, so modifying the /etc/hosts file is required.

The problem is that when using the format [IP Address] [Hostname] [Aliases] in /etc/hosts Docker Engine is only able to resolve the [Hostname], not any of the [Aliases]. If the line is split to be multiple [IP Address] [Hostname] then Docker Engine is correctly able to resolve all of them.

Steps to reproduce the behavior

1. Set up a registry as a pull through cache
2. Declare the IP and hostname in /etc/hosts (a bogus hostname can be provided, to then allow the correct hostname to be declared as an alias.
3. Configure Docker for Mac to use the registry as a mirror, using the hostname declared as an alias
4. Attempt to pull an image that has not already been pulled onto the local host

[rogaha]

@flxsource thanks for the reporting the issue, I've raised another issue on the vpnkit repository: moby/vpnkit#162. We will let you know as soon as it gets fixed!

[djs55]

I've merged a fix for this into the master branch which should be released in beta 37, due in a couple of weeks.

[yallop]

@flxsource, could you please confirm that the latest beta (39) resolves the problem?

[samoht]

Both stable and channels should now contain the fix, so closing. @flxsource please re-open that issue if the fix doesn't work for you. Thanks!

[docker-robott]

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