Docker version 1.13.1, Docker Swarm, jwilder/nginx-proxy will not start as a docker service

Question

I'm trying to setup an Elasticsearch cluster on Docker following this guide: https://sematext.com/blog/2016/12/12/docker-elasticsearch-swarm/

But I'm consistently getting an error about /tmp/docker.sock after creating the jwilder/nginx-proxy service. The below console snip is from a freshly installed and updated CentOS7. I installed docker via yum following the instructions here: https://docs.docker.com/engine/installation/linux/centos/

[root@centos7]# docker -v
Docker version 1.13.1, build 092cba3
[root@centos7]#
[root@centos7]# docker service create --mode global \
> --name proxy -p 80:80 \
> --network elasticsearch-frontend \
> --network elasticsearch-backend  \
> --mount type=bind,bind-propagation=rshared,src=/var/run/docker.sock,target=/tmp/docker.sock:ro \
> jwilder/nginx-proxy
xbhj4rzjyuu0k8maf1ha5fmgs
[root@centos7]# docker service ls
ID            NAME   MODE    REPLICAS  IMAGE
xbhj4rzjyuu0  proxy  global  0/1       jwilder/nginx-proxy:latest
[root@centos7]# docker ps -a
CONTAINER ID        IMAGE                                                                                         COMMAND                  CREATED             STATUS                      PORTS               NAMES
7ba303e0f8b6        jwilder/nginx-proxy@sha256:9a2d63aad9068f817c705965f41f2f32fa0bbef6b217ae5c9b2340ef23e3dcba   "/app/docker-entry..."   2 seconds ago       Created                                         proxy.kifcc5gbdcxz5ixsbx7sl1cv8.zuizhtt7q94nluuudlgjgy1yi
2fe655a93aa4        jwilder/nginx-proxy@sha256:9a2d63aad9068f817c705965f41f2f32fa0bbef6b217ae5c9b2340ef23e3dcba   "/app/docker-entry..."   10 seconds ago      Exited (1) 3 seconds ago                        proxy.kifcc5gbdcxz5ixsbx7sl1cv8.baqn1204spbw5v6qxx6qjx327
7894fd0e1dee        jwilder/nginx-proxy@sha256:9a2d63aad9068f817c705965f41f2f32fa0bbef6b217ae5c9b2340ef23e3dcba   "/app/docker-entry..."   18 seconds ago      Exited (1) 11 seconds ago                       proxy.kifcc5gbdcxz5ixsbx7sl1cv8.6s9u0q0y1kjelebszheius2es
51840cca0d32        jwilder/nginx-proxy@sha256:9a2d63aad9068f817c705965f41f2f32fa0bbef6b217ae5c9b2340ef23e3dcba   "/app/docker-entry..."   26 seconds ago      Exited (1) 19 seconds ago                       proxy.kifcc5gbdcxz5ixsbx7sl1cv8.wlwy723ts9kw00sgyu3s5f985
d52fd18567a9        jwilder/nginx-proxy@sha256:9a2d63aad9068f817c705965f41f2f32fa0bbef6b217ae5c9b2340ef23e3dcba   "/app/docker-entry..."   34 seconds ago      Exited (1) 27 seconds ago                       proxy.kifcc5gbdcxz5ixsbx7sl1cv8.wa5jk9xnly1tdxpbvonnjmoty
[root@centos7]# docker logs 2fe655a93aa4
ERROR: you need to share your Docker host socket with a volume at /tmp/docker.sock
Typically you should run your jwilder/nginx-proxy with: `-v /var/run/docker.sock:/tmp/docker.sock:ro`
See the documentation at http://git.io/vZaGJ
[root@centos7]#

The jwilder/nginx-proxy container works when launched as a single container using the -v option to mount docker.sock.

I've scoured google (the Docker docs, the jwilder/nginx-proxy git) looking for what would cause this and I've come up with nothing. Does anyone see something wrong? I'm new to docker, so maybe I'm missing something easy.

Thanks in advance! :-)

Answer 1

Instead of making a read-only mount of /var/run/docker.sock to /tmp/docker.sock , you are making a mount of /var/run/docker.sock to /tmp/docker.sock:ro , hence the application cries.

To rectify this, make a slight modification. Replace...

--mount type=bind,bind-propagation=rshared,src=/var/run/docker.sock,target=/tmp/docker.sock:ro

...with:

--mount type=bind,bind-propagation=rshared,src=/var/run/docker.sock,target=/tmp/docker.sock,ro=1

From the documentation :

readonly or ro: The Engine mounts binds and volumes read-write unless readonly option is given when mounting the bind or volume. When true or 1 or no value the bind or volume is mounted read-only. When false or 0 the bind or volume is mounted read-write.