PCA Promql Practice Question
You are using the 'predict_linear()' function to forecast disk space exhaustion based on the metric 'node_filesystem_free_bytes'. What type of input data does predict_linear require?
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
✓
A range vector of gauge values and a time duration scalar.
predict_linear predicts the value of a gauge metric 't' seconds into the future based on a range vector using linear regression.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
An instant vector representing current disk space.
Why it's wrong here
predict_linear takes a range vector to perform linear regression.
- ✓
A range vector of gauge values and a time duration scalar.
Why this is correct
predict_linear takes a range vector (e.g., [1h]) and a scalar duration, requiring gauge inputs.
- ✗
Two instant vectors joined via an 'on' clause.
Why it's wrong here
It takes a single range vector argument.
- ✗
A counter range vector wrapped in a rate() function.
Why it's wrong here
predict_linear is designed for gauges, not rates of counters.
About these practice questions
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed August 2026 · checked against the official CNCF / Linux Foundation exam blueprint
This PCA practice question is part of Courseiva's free CNCF / Linux Foundation 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 PCA exam.