Deploying Pi-hole within a Kubernetes environment transforms a simple network-level ad blocker into an enterprise-grade DNS infrastructure. While Pi-hole is traditionally recognized as a lightweight DNS proxy designed for the Raspberry Pi, its architecture allows for deployment across various homelab environments, including Docker images and full-scale Kubernetes clusters. This transition allows users to move beyond the limitations of browser extensions and manual /etc/hosts modifications on individual laptops, extending ad-blocking, tracker-blocking, and malware-filtering capabilities to every device on a network, including smartphones and tablets.
The shift to Kubernetes is often driven by the desire for high availability (HA) and the ability to manage DNS as code. By leveraging a container orchestration platform, a user can ensure that their DNS services remain operational even if a single node fails. This is a significant upgrade over a single-point-of-failure Raspberry Pi setup, although the transition introduces specific technical hurdles related to networking, state management, and the inherent nature of DNS traffic within a virtualized cluster.
Infrastructure Foundations and K3s
The underlying platform for a Kubernetes-based Pi-hole deployment often begins with K3s. K3s is an open-source, compliant distribution of Kubernetes that is specifically engineered to be lightweight. This makes it an ideal choice for various hardware environments, ranging from old laptops to ARM-based Raspberry Pi 4 devices.
When aiming for an enterprise-style deployment, installing K3s with etcd is recommended to support high availability. By using etcd as the datastore instead of the default SQLite, the cluster can maintain its state across multiple master nodes, ensuring that the control plane remains functional even if one node goes offline. This architectural choice provides the stability required to host a critical network service like DNS, where any outage results in a complete loss of internet connectivity for all connected clients.
For those new to running Kubernetes on bare metal, tools like Lens Desktop are highly recommended. Lens provides a graphical interface for managing the cluster, which significantly lowers the learning threshold for users who are not yet comfortable exclusively using the command line.
Helm Deployment and Configuration
The most efficient way to deploy Pi-hole in Kubernetes is through the use of Helm, which functions as a package manager for Kubernetes. Helm uses "Charts," which are pre-packaged sets of Kubernetes resources. Specifically, the mojo2600/pihole chart is widely utilized by the community to simplify the deployment process.
To initiate the deployment, the Helm repository must first be added to the local environment using the following command:
helm repo add mojo2600 https://mojo2600.github.io/pihole-kubernetes/
Before executing the installation, users can inspect the available customizable values to tailor the deployment to their specific network needs:
helm show values mojo2600/pihole
The deployment process requires several preparatory steps to ensure isolation and security:
Create a dedicated namespace to isolate Pi-hole from other cluster services:
kubectl create namespace piholeCreate a secret to store the administrative password, ensuring it is not stored in plain text within the configuration files:
kubectl -n pihole create secret generic pihole-admin --from-literal='password=<admin-pwd>'
Technical Analysis of the Values Configuration
The values.yaml file is the central point of configuration for the Pi-hole Helm chart. A detailed analysis of the required configurations reveals how the service integrates with the broader network.
| Configuration Parameter | Value/Setting | Purpose |
|---|---|---|
| replicaCount | 1 (Adjustable) | Defines the number of Pi-hole pods running. |
| image tag | "2023.03.1" | Fixes the version to ensure stability. |
| serviceDhcp | disabled | Offloaded to external hardware like Edge Routers. |
| serviceDns type | LoadBalancer | Exposes DNS services outside the cluster. |
| serviceWeb type | LoadBalancer | Exposes the Admin GUI outside the cluster. |
| loadBalancerIP | 192.168.10.250 | Assigns a consistent IP for network-wide DNS. |
| cpu limits | 200m | Caps CPU usage to prevent resource exhaustion. |
| memory limits | 256Mi | Caps RAM usage to ensure cluster stability. |
The use of LoadBalancer for both DNS and Web services is critical. In many homelab environments, this is achieved using MetalLB. To allow both the DNS service and the Web service to share the same IP address, specific annotations must be applied in the values.yaml file:
metallb.universe.tf/allow-shared-ip: pihole
This configuration ensures that clients only need to point to a single IP address to receive both DNS resolution and access to the management interface.
High Availability and Data Integrity Challenges
Achieving true high availability (HA) for Pi-hole in Kubernetes introduces several non-trivial challenges that require specific workarounds.
The Automation Gap in GUI
Since Pi-hole v5, the ability to add blocklists has been moved exclusively to the Graphical User Interface (GUI). This creates a friction point for Kubernetes users who prefer an "Infrastructure as Code" approach. Because the blocklist cannot be updated via configuration files or API calls without manual intervention in the GUI, automation is limited. This forces the administrator to manually click through the interface to update lists, which contradicts the automation philosophy of Kubernetes.
Database Constraints with SQLite
Pi-hole relies on SQLite for its internal database. SQLite is a file-based database and is not designed for concurrent access from multiple pods. This becomes a significant bottleneck when attempting to scale Pi-hole horizontally. Since Pi-hole cannot be easily redirected to use a high-availability MariaDB cluster for its core functions, the reliance on SQLite creates a constraint on how state is managed across multiple replicas.
The Source IP Loss Problem
A common issue when routing DNS requests through Kubernetes infrastructure—specifically through Load Balancers, Ingress, and Services—is the loss of the client's source IP address. When the request hits the Pi-hole pod, the source IP is often seen as the IP of the Load Balancer rather than the actual device. This makes it impossible to track which device is making which request, effectively neutralizing the per-client filtering and logging capabilities of Pi-hole.
Storage and Persistence Strategies
To ensure that DNS records, whitelists, and blocklists are not lost when a pod restarts, persistent volume storage is mandatory. Using the persistentVolumeClaim setting in the Helm chart allows the data to persist beyond the lifecycle of the container.
For environments requiring higher reliability or shared access across nodes, using a persistent volume storage provider is recommended. Examples include:
- NFS (Network File System)
- Longhorn
These providers ensure that the Pi-hole volume is available regardless of which node the pod is scheduled on, which is essential for maintaining consistency in a multi-node cluster.
Advanced Web Interface Access and Ingress
While the Helm chart allows for a LoadBalancer for the web interface, many power users prefer managing access via an Nginx Ingress Controller. This allows for better control over access and the use of friendly local DNS names instead of raw IP addresses.
An example Ingress configuration for Pi-hole looks as follows:
yaml
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: pihole-web
namespace: pihole
annotations:
nginx.ingress.kubernetes.io/whitelist-source-range: 127.0.0.1/8,192.168.0.0/16
spec:
ingressClassName: public
rules:
- host: YOUR.LOCAL.DNS.NAME
http:
paths:
- backend:
service:
name: pihole-web
port:
number: 80
path: /
pathType: Prefix
To make this configuration functional, the user must add the local domain name associated with the Ingress controller's service IP address to the local machine's hosts file. On Linux, this is /etc/hosts, and on macOS, it is /private/etc/hosts. Once configured, the dashboard is accessible at http://your.domain.name/admin.
DNS over HTTPS (DoH) Integration
To enhance security and privacy, the Pi-hole deployment can be configured to use DNS over HTTPS (DoH). This ensures that upstream DNS requests are encrypted, preventing Internet Service Providers (ISPs) or other eavesdroppers from monitoring DNS queries.
In a Kubernetes setup, this is typically implemented using a Cloudflare tunnel. By routing upstream requests through DoH, the user adds a layer of security that protects the network from DNS spoofing and hijacking, while maintaining the ad-blocking capabilities of Pi-hole.
Implementation and Network Integration
Once the cluster is deployed and the pods are running, the final step is to integrate the service into the rest of the network. There are two primary methods for achieving this:
- Local Device Configuration: Manually setting the Pi-hole LoadBalancer IP as the DNS server in the network settings of individual devices.
- Global Router Configuration: Setting the Pi-hole IP as the default DNS server in the WiFi router's DHCP settings. This automatically pushes the DNS configuration to every device that joins the network, providing a seamless experience.
Redundancy and Disaster Recovery
Despite the high availability provided by Kubernetes, a "fail-safe" approach is recommended. Kubernetes clusters can suffer from catastrophic failures, or the administrator may simply be unable to troubleshoot the cluster during a day job.
To mitigate this, it is advised to maintain a separate, static installation of Pi-hole on a low-cost Raspberry Pi. This standalone device serves as the secondary DNS server. To avoid the tedious process of managing two separate sets of ad lists, whitelists, and local DNS entries, a tool called orbital-sync can be deployed via Docker Compose on the secondary Raspberry Pi.
orbital-sync functions by:
- Creating a backup of the primary Pi-hole (the Kubernetes instance).
- Automatically restoring that backup to the secondary Pi-hole.
This creates a hybrid architecture: a highly available, orchestrated primary system and a simple, reliable static secondary system.
Final Analysis of the Kubernetes Approach
The deployment of Pi-hole in Kubernetes represents a shift from simple home networking to professional-grade infrastructure management. By utilizing K3s, Helm, and MetalLB, users can create a DNS environment that is scalable, resilient, and highly configurable.
However, the transition is not without its costs. The complexities of SQLite state management and the loss of client source IPs are inherent challenges that require careful planning. The reliance on the GUI for blocklist management further highlights the gap between the current Pi-hole software architecture and the ideals of a fully automated Kubernetes ecosystem.
Ultimately, the value of this setup lies in the educational and operational experience. For the home lab enthusiast, it provides a sandbox to master Ingress controllers, persistent volume claims, and LoadBalancer configurations. For the household, it provides a robust, centralized way to scrub the internet of trackers and advertisements, ensuring a cleaner and faster browsing experience across all connected devices. The combination of a K3s-based primary cluster and a standalone Raspberry Pi backup via orbital-sync represents the gold standard for domestic DNS availability.