Two errors you can fix like that
#1 set privileged = true
2017-11-21T15:17:26.802822881Z mount: permission denied (are you root?)
2017-11-21T15:17:26.803090353Z Could not mount /sys/kernel/security.
2017-11-21T15:17:26.803107368Z AppArmor detection and --privileged mode might break.
2017-11-21T15:17:26.806984781Z mount: permission denied (are you root?)
#2 Mount /var/run/docker.sock as a volume
Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?
/etc/gitlab-runner/config.toml
concurrent = 4
check_interval = 0
[[runners]]
limit = 4
name = "fancy name"
url = "https://www.gitlab.com"
token = "secret token"
executor = "docker"
[runners.docker]
tls_verify = false
image = "alpine:3.4"
privileged = true
disable_cache = false
volumes = ["/cache", "/var/run/docker.sock:/var/run/docker.sock"]
[runners.cache]
Insecure = false