KCNA Kubernetes Fundamentals Practice Question
Which Kubernetes controller ensures that a specified number of pod replicas are running at all times?
⚠ Common exam trap
CNCF often tests the distinction between ReplicaSet and ReplicationController, trapping candidates who think ReplicationController is still the primary controller for replica management, when in fact ReplicaSet is the modern, recommended controller.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
ReplicaSet
A ReplicaSet is the Kubernetes controller that ensures a specified number of pod replicas are running at all times. It uses a label selector to match pods and maintains the desired replica count by creating or deleting pods as needed. ReplicaSet is the successor to ReplicationController and is primarily used by Deployments to manage pod scaling and self-healing.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
ReplicaSet
Why this is correct
A ReplicaSet's reconciliation loop continuously compares the desired replica count in its specification against observed pod counts, creating or deleting pods to match. This directly satisfies the stem's requirement for maintaining a specified number of pod replicas at all times, unlike Deployments (which manage ReplicaSets) or DaemonSets (one pod per node).
- ✗
Job
Why it's wrong here
Job runs pods to completion for batch or one-off tasks, then stops; it does not sustain a replica count over time. It is tempting because it does create and track pods, and it would be correct for a finite workload such as a database migration or report generation.
- ✗
ReplicationController
Why it's wrong here
ReplicationController does maintain a specified replica count, but it predates Deployments and lacks rolling-update and selector features, so current guidance favours ReplicaSet managed by a Deployment. It is tempting because it historically performed exactly this role, and it would be correct on legacy clusters without Deployment support.
- ✗
DaemonSet
Why it's wrong here
DaemonSet runs one pod copy on every node, or a selected subset, for node-level agents such as log shippers; it does not maintain a requested replica count. It is tempting because it does guarantee pod presence, and it would be correct when every node needs the same workload.
Go deeper
Related to this question
Learn chapter
Pods and Workload Management
Key term
ReplicaSet and Replication
A ReplicaSet ensures a specified number of identical pod instances are running at all times in Kubernetes, using replication to maintain availability and stability.
Key term
Horizontal Pod Autoscaling
Horizontal Pod Autoscaling automatically adjusts the number of pod replicas in a Kubernetes cluster based on observed CPU, memory, or custom metrics.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This KCNA practice question is part of Courseiva's free CNCF certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the KCNA exam.