Dependencies in Slackbuilds for docker-17.09.1 2018-01-11:

docker
  containerd
    runc
      google-go-lang
      libseccomp
  tini
  docker-proxy
    google-go-lang

After install, according to the slackbuild package:

groupadd -r -g 281 docker            # Create the docker group. Groupnumber seems preset
usermod -a -G docker <your_username> # Add user(s) to the docker group

To have the docker daemon start and stop with your host,
add to /etc/rc.d/rc.local:

if [ -x /etc/rc.d/rc.docker ]; then
/etc/rc.d/rc.docker start
fi

and to /etc/rc.d/rc.local_shutdown (creating it if needed):

if [ -x /etc/rc.d/rc.docker ]; then
/etc/rc.d/rc.docker stop
fi

Docker client and server share the same binary.

Docker works fine in Slackware 14.2 with Generic Kernel not with Huge Kernel.¹⁾. Made the same experience — 2017-02-02

Config file for the daemon is /etc/default/docker. This file is sourced by /etc/rc.d/rc.docker.

Default data (images usw) directory is /var/lib/docker. This can be changed with –graph option in /etc/default/docker.

There is also /etc/docker/. Purpose yet unknown.