Pods fail to lookup web server with hostname after helm installation

Hi, there!

I tried to deploy gitlab’s helm chart on a single-node cluster with default settings. Here’s the installation command:

helm install gitlab gitlab/gitlab\
  --timeout 600s \
  --set certmanager-issuer.email=MY_EMAIL

Everything seemed fine but I saw some errors in the log.

Here’s a snippet from cert-manager’s log:

I1122 15:59:25.667719       1 ingress.go:90] cert-manager/controller/challenges/http01/selfCheck/http01/ensureIngress "msg"="found one existing HTTP01 solver ingress" "dnsName"="registry.example.com" "related_resource_kind"="Ingress" "related_resource_name"="cm-acme-http-solver-pkf5r" "related_resource_namespace"="kube-system" "related_resource_version"="v1" "resource_kind"="Challenge" "resource_name"="gitlab-registry-tls-jhpbk-3586564254-1143666161" "resource_namespace"="kube-system" "resource_version"="v1" "type"="HTTP-01"
E1122 15:59:25.700472       1 sync.go:185] cert-manager/controller/challenges "msg"="propagation check failed" "error"="failed to perform self check GET request 'http://registry.example.com/.well-known/acme-challenge/UNPfb1Db-JnSiCoSRuyei7OOoJpfgLlwnTmhoKQBoz0': Get \"http://registry.example.com/.well-known/acme-challenge/UNPfb1Db-JnSiCoSRuyei7OOoJpfgLlwnTmhoKQBoz0\": dial tcp: lookup registry.example.com on 192.168.0.10:53: no such host" "dnsName"="registry.example.com" "resource_kind"="Challenge" "resource_name"="gitlab-registry-tls-jhpbk-3586564254-1143666161" "resource_namespace"="kube-system" "resource_version"="v1" "type"="HTTP-01"

Another from gitlab-runner:

ERROR: Registering runner... failed                 runner=kwMT7PGz status=couldn't execute POST against https://gitlab.example.com/api/v4/runners: Post https://gitlab.example.com/api/v4/runners: dial tcp: lookup gitlab.example.com on 192.168.0.10:53: no such host
PANIC: Failed to register the runner. You may be having network problems.

I guess the domain names are not registered at the cluster’s internal DNS server (CoreDNS in my case). Could you give some hints about what might went wrong with my deployment? Thanks!