☸️ How /etc/resolv.conf Works in Kubernetes

How This Works in Kubernetes

Now that we understand /etc/resolv.conf on a laptop, let’s see how the same concept works inside Kubernetes.

Even inside a Kubernetes Pod, the system still uses /etc/resolv.conf. But instead of pointing to Google DNS or your router, it points to an internal DNS service.

Example Inside a Pod

Run this inside a Pod: 

kubectl exec -it <pod> -- cat /etc/resolv.conf

You might see:

nameserver 1xx.xx.0.10
search default.svc.cluster.local svc.cluster.local cluster.local
options ndots:5

What Changed?

  • nameserver → now points to CoreDNS
  • search → helps resolve internal service names

What is CoreDNS?

CoreDNS is the DNS server inside Kubernetes. It knows how to resolve service names like user-service.
---

Real Example in Kubernetes

App inside Pod
        ↓
Checks /etc/resolv.conf
        ↓
Finds nameserver (CoreDNS)
        ↓
Asks: "What is user-service?"
        ↓
CoreDNS responds:
user-service.default.svc.cluster.local → 10.x.x.x
        ↓
App connects to that IP

What is the "search" field?

The search field helps resolve short names automatically. 

user-service

Kubernetes expands it to:

user-service.default.svc.cluster.local
user-service.svc.cluster.local
This is why you can use short names like user-service inside Kubernetes.

Why This Matters

  • App cannot find services ❌
  • Database connections fail ❌
  • Health checks fail ❌
  • Rollouts fail ❌

Connecting to Real Issues

Errors like: 

connection refused
connection reset by peer

can sometimes happen if DNS resolution is delayed or failing during startup.

Even small DNS delays can make a healthy app look "not ready" to Kubernetes.

Final Takeaway

Laptop → asks external DNS
Kubernetes Pod → asks CoreDNS

Same concept, different DNS server.

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