Install Docker on MT2500

I have installed dockerd and luci-app-dockerman , and I can see docker in luci, however, I keep stuck at the setting page, I wonder where it went wrong?
I have tried to fill out Defalut bridge and client connection, but nothing happened after that.

When I tried to use docker command line, it said

Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?