---
reviewers:
- bowei
- zihongz
title:  Debugging DNS Resolution
content_type: task
min-kubernetes-server-version: v1.6
weight: 170
---

<!-- overview -->
This page provides hints on diagnosing DNS problems.

## {{% heading "prerequisites" %}}

{{< include "task-tutorial-prereqs.md" >}}  
Your cluster must be configured to use the CoreDNS
{{< glossary_tooltip text="addon" term_id="addons" >}} or its precursor,
kube-dns.  

{{% version-check %}}

<!-- steps -->

### Create a simple Pod to use as a test environment

{{% code_sample file="admin/dns/dnsutils.yaml" %}}

{{< note >}}
This example creates a pod in the `default` namespace. DNS name resolution for 
services depends on the namespace of the pod. For more information, review
[DNS for Services and Pods](/docs/concepts/services-networking/dns-pod-service/#what-things-get-dns-names). 
{{< /note >}}

Use that manifest to create a Pod:

```shell
kubectl apply -f https://k8s.io/examples/admin/dns/dnsutils.yaml
```
```
pod/dnsutils created
```
…and verify its status:
```shell
kubectl get pods dnsutils
```
```
NAME       READY     STATUS    RESTARTS   AGE
dnsutils   1/1       Running   0          <some-time>
```

Once that Pod is running, you can exec `nslookup` in that environment.
If you see something like the following, DNS is working correctly.

```shell
kubectl exec -i -t dnsutils -- nslookup kubernetes.default
```
```
Server:    10.0.0.10
Address 1: 10.0.0.10

Name:      kubernetes.default
Address 1: 10.0.0.1
```

If the `nslookup` command fails, check the following:

### Check the local DNS configuration first

Take a look inside the resolv.conf file.
(See [Customizing DNS Service](/docs/tasks/administer-cluster/dns-custom-nameservers) and
[Known issues](#known-issues) below for more information)

```shell
kubectl exec -ti dnsutils -- cat /etc/resolv.conf
```

Verify that the search path and name server are set up like the following
(note that search path may vary for different cloud providers):

```
search default.svc.cluster.local svc.cluster.local cluster.local google.internal c.gce_project_id.internal
nameserver 10.0.0.10
options ndots:5
```

Errors such as the following indicate a problem with the CoreDNS (or kube-dns)
add-on or with associated Services:

```shell
kubectl exec -i -t dnsutils -- nslookup kubernetes.default
```
```
Server:    10.0.0.10
Address 1: 10.0.0.10

nslookup: can't resolve 'kubernetes.default'
```

or

```shell
kubectl exec -i -t dnsutils -- nslookup kubernetes.default
```
```
Server:    10.0.0.10
Address 1: 10.0.0.10 kube-dns.kube-system.svc.cluster.local

nslookup: can't resolve 'kubernetes.default'
```

### Check if the DNS pod is running

Use the `kubectl get pods` command to verify that the DNS pod is running.

```shell
kubectl get pods --namespace=kube-system -l k8s-app=kube-dns
```
```
NAME                       READY     STATUS    RESTARTS   AGE
...
coredns-7b96bf9f76-5hsxb   1/1       Running   0           1h
coredns-7b96bf9f76-mvmmt   1/1       Running   0           1h
...
```

{{< note >}}
The value for label `k8s-app` is `kube-dns` for both CoreDNS and kube-dns deployments.
{{< /note >}}


If you see that no CoreDNS Pod is running or that the Pod has failed/completed,
the DNS add-on may not be deployed by default in your current environment and you
will have to deploy it manually.

### Check for errors in the DNS pod

Use the `kubectl logs` command to see logs for the DNS containers.

For CoreDNS:
```shell
kubectl logs --namespace=kube-system -l k8s-app=kube-dns
```

Here is an example of a healthy CoreDNS log:

```
.:53
2018/08/15 14:37:17 [INFO] CoreDNS-1.2.2
2018/08/15 14:37:17 [INFO] linux/amd64, go1.10.3, 2e322f6
CoreDNS-1.2.2
linux/amd64, go1.10.3, 2e322f6
2018/08/15 14:37:17 [INFO] plugin/reload: Running configuration MD5 = 24e6c59e83ce706f07bcc82c31b1ea1c
```

See if there are any suspicious or unexpected messages in the logs.

### Is DNS service up?

Verify that the DNS service is up by using the `kubectl get service` command.