Kubernetes Service Types and DNS-Based Discovery#

Services are the stable networking abstraction in Kubernetes. Pods come and go, but a Service gives you a consistent DNS name and IP address that routes to the right set of pods. Choosing the wrong Service type or misunderstanding DNS discovery is behind a large percentage of connectivity failures.

Service Types#

ClusterIP (Default)#

ClusterIP creates an internal-only virtual IP. Only pods inside the cluster can reach it. This is what you want for internal communication between microservices.

Minikube Networking: Services, Ingress, DNS, and LoadBalancer Emulation#

Minikube networking behaves differently from cloud Kubernetes in ways that cause confusion. LoadBalancer services do not get external IPs by default, the minikube IP may or may not be directly reachable from your host depending on the driver, and ingress requires specific addon setup. Understanding these differences prevents hours of debugging connection timeouts to services that are actually running fine.

How Minikube Networking Works#

Minikube creates a single node (a VM or container depending on the driver) with its own IP address. Pods inside the cluster get IPs from an internal CIDR. Services get ClusterIPs from another internal range. The bridge between your host machine and the cluster depends entirely on which driver you use.

Unit Types#

systemd manages the entire system through “units,” each representing a resource or service. The most common types:

• service: Daemons and long-running processes (nginx, postgresql, your application).
• timer: Scheduled execution, replacing cron. More flexible and better integrated with logging.
• socket: Network sockets that trigger service activation on connection. Enables lazy startup and zero-downtime restarts.
• target: Groups of units that represent system states (multi-user.target, graphical.target). Analogous to SysV runlevels.
• mount: Filesystem mount points managed by systemd.
• path: Watches filesystem paths and activates units when changes occur.

Unit files live in three locations, in order of precedence: /etc/systemd/system/ (local admin overrides), /run/systemd/system/ (runtime, non-persistent), and /usr/lib/systemd/system/ (package-installed defaults). Always put custom units in /etc/systemd/system/.