Cannot read config file when referenced through nested symbolic links

[HCanber]

Version: 1.0.1, 1.0.2

Description of the Issue (and unexpected/desired result)

Consul does not start as it's unable to read config files for the specific structure below. It works in 1.0.0.

I have a structure with symbolic links that looks like this:

/
+-- consul
    +-- config
        +-- dir
        |   +-- server.json
        +-- link_dir -> dir
        +-- server.json -> link_dir/server.json

This kind of structure is created by Kuberenetes when mounting volumes, see kelseyhightower/consul-on-kubernetes#23
The structure above is exactly the same as in the linked issue, except I've simplified the names.

Reproduction steps

1. Create a file named Dockerfile with the content

   FROM consul:1.0.1
   RUN mkdir -p /consul/config/dir && \
     echo '{"node_name":"foobar"}' > /consul/config/dir/server.json && \
     ln -s dir /consul/config/link_dir && \
     ln -s link_dir/server.json /consul/config/server.json

2. Build image:

   docker build -t consul-test .

3. See content of /consul/config

   docker run -t --name=dev-consul --entrypoint ls consul-test -al /consul/config/  &&\
   docker rm dev-consul >/dev/null

   total 12
   drwxr-xr-x    1 consul   consul        4096 Dec 15 15:40 .
   drwxr-xr-x    1 consul   consul        4096 Dec  1 19:14 ..
   drwxr-xr-x    2 root     root          4096 Dec 15 15:40 dir
   lrwxrwxrwx    1 root     root             3 Dec 15 15:40 link_dir -> dir
   lrwxrwxrwx    1 root     root            20 Dec 15 15:40 server.json -> link_dir/server.json
   

4. See the content of server.json

   docker run -t --name=dev-consul --entrypoint cat consul-test  /consul/config/server.json  &&\
   docker rm dev-consul >/dev/null

   {"node_name":"foobar"}

5. Start consul with server.json as config file

   docker run --name=dev-consul -e CONSUL_BIND_INTERFACE=eth0 consul-test agent -dev -client 0.0.0.0 -config-file=/consul/config/server.json -log-level=TRACE ;\
   docker rm dev-consul >/dev/null

   It fails with:

   ==> Found address '172.17.0.2' for interface 'eth0', setting bind option...
   ==> config: ReadFile failed on /consul/config/link_dir: read /consul/config/link_dir: is a directory
   

6. To prove that it works in version 1.0.0, modify the content of Dockerfile to use image consul:1.0.0. Build the image and start Consul:

   docker build -t consul-test .
   docker run --name=dev-consul -e CONSUL_BIND_INTERFACE=eth0 consul-test agent -dev -client 0.0.0.0 -config-file=/consul/config/server.json -log-level=TRACE ;\
   docker rm dev-consul >/dev/null

   Consul will start correctly. Press Ctrl+C to exit

7. To cleanup execute

   docker rmi consul-test

I have verified that it does not work in version 1.0.2 either. I used 1.0.1 in this example as 1.0.2 hasn't been released to Docker Hub.

[jameshartig]

The problem is that the consul Dockerfile by default (without a way to prevent it) looks for config files in /consul/config (see: https://github.com/hashicorp/docker-consul/blob/master/0.X/docker-entrypoint.sh#L45). Since you have non files in there, it fails. I'm working on a PR.