Where to seek error logs?

Hi!

I am new to Gitlab CI, and would like to set up a runner. I created a gitlab runner in a docker-compose.yml file:

version: '3'
services:
  gitlabrunner:
    image: 'gitlab/gitlab-runner:latest'
    deploy:
      resources:
        limits:
          memory: '${MEMORY_LIMIT}'
          cpus: '${CPUS}'
    container_name: gitlab-runner
    restart: always
    volumes:
      - config:/etc/gitlab-runner'
      - '/var/run/docker.sock:/var/run/docker.sock'
  
volumes:
  config:

I registered the runner (note: the warning is caused by the resource limits without swarm mode):

After that I have this one one container related to gitlab-runner:

gitlab-runner@iinfra1:~/workload$ docker ps
CONTAINER ID        IMAGE                             COMMAND                  CREATED             STATUS                PORTS                                                NAMES
7568bbe44d66        gitlab/gitlab-runner:latest       "/usr/bin/dumb-init …"   10 minutes ago      Up 10 minutes                                                              gitlab-runner

But when I commit something to a repo which has the following dummy .gitlab-ci.yml:

build:
  script:
    - echo "Hello World"

I got a pending job:


image

All of my docker logs are here:

gitlab-runner@iinfra1:~/workload$ docker-compose logs -ft
WARNING: Some services (gitlabrunner) use the 'deploy' key, which will be ignored. Compose does not support 'deploy' configuration - use `docker stack deploy` to deploy to a swarm.
Attaching to gitlab-runner
gitlab-runner   | 2020-09-25T16:20:35.133909084Z Runtime platform                                    arch=amd64 os=linux pid=6 revision=4e1f20da version=13.4.0
gitlab-runner   | 2020-09-25T16:20:35.133944604Z Starting multi-runner from /etc/gitlab-runner/config.toml...  builds=0
gitlab-runner   | 2020-09-25T16:20:35.133949365Z Running in system-mode.                            
gitlab-runner   | 2020-09-25T16:20:35.133965471Z                                                    
gitlab-runner   | 2020-09-25T16:20:35.134002343Z Configuration loaded                                builds=0
gitlab-runner   | 2020-09-25T16:20:35.134126987Z listen_address not defined, metrics & debug endpoints disabled  builds=0
gitlab-runner   | 2020-09-25T16:20:35.134137690Z [session_server].listen_address not defined, session endpoints disabled  builds=0

I am totally clueless where can I find the source of error, where to see logfiles.