Use /var/run/docker.sock as backend server

[Tardo]

In 2.2 version, because the Dockerfile uses "root" user, you can mount "/var/run/docker.sock" and read it... but in older versions the user used is "haproxy"...

How i can still read to /var/run/docker.sock ? I need change the user to root in my Dockerfile?

Thanks.

[tianon]

I don't recommend running haproxy as root (nor exposing your Docker socket externally without some strict authentication, in case that's what you're doing here, since access to it is root-equivilant 😬), but you should be able to do so with --user on docker run or user: in docker-compose.yml.

Another option would be to create a docker group inside the container/image with a GID that matches the GID of the docker group on your host and then adding the haproxy user to it (or running explicitly with --user haproxy:GID, as in, --user haproxy:998 with my example below):

$ stat --format '%g' /var/run/docker.sock
998

[tianon]

(In the future, these sorts of questions/requests would be more appropriately posted to a dedicated support forum, such as the Docker Community Slack, Server Fault, Unix & Linux, or Stack Overflow.)