EX294 Coordinate rolling updates Practice Question
Which THREE statements correctly describe the behavior of the 'serial' keyword in Ansible? (Choose exactly three.)
⚠ Common exam trap
Many candidates confuse 'serial' with a task-level concurrency control or assume it applies globally across all plays, when in fact it is a per-play batch size setting that controls how many hosts execute the entire play simultaneously.
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
✓
It can be set as a percentage of the total hosts.
Option A is correct because the serial keyword accepts a percentage value (e.g., serial: 25%) that Ansible interprets as a fraction of the total hosts in the play, batching them accordingly. Option B is correct because serial defines the number of hosts (or batch size) that Ansible targets per play iteration, so the play runs on a subset of hosts at a time rather than all at once. Option C is correct because serial is commonly paired with max_fail_percentage, which aborts the play if failures within a serial batch exceed the given threshold, enabling controlled rolling updates. Option D is incorrect because serial controls host batching, not task concurrency; it does not guarantee only one task runs across all hosts at any time. Option E is incorrect because serial is set at the play level and applies only to that specific play, not globally to all plays in a playbook.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
It can be set as a percentage of the total hosts.
Why this is correct
Ansible accepts serial as an integer or a percentage, so specifying 25% runs the play across a quarter of the matched hosts per batch. This satisfies the stem's requirement for a statement describing serial's percentage-based behaviour, distinct from fixed host counts.
- ✓
It causes the playbook to run on a subset of hosts at a time.
Why this is correct
The serial keyword defines how many hosts Ansible targets per play iteration, so setting serial to a number or percentage runs the play on that subset before proceeding, satisfying the batching behaviour described in the stem.
- ✓
It can be combined with max_fail_percentage to control failure thresholds.
Why this is correct
Serial batches combine with max_fail_percentage, which aborts the play once failures within a batch exceed that threshold. This satisfies the stem's requirement for a statement describing serial's interaction with failure thresholds, distinct from its batching and percentage behaviours.
- ✗
It guarantees that only one task runs across all hosts at any time.
Why it's wrong here
serial limits how many hosts a play targets per batch, not task concurrency; within a batch, tasks still run across all those hosts simultaneously. It is tempting because serial=1 does restrict a play to one host, but that is per-batch host count, not a global single-task guarantee.
- ✗
It applies globally to all plays in the playbook.
Why it's wrong here
serial is declared at play level and affects only that play's host batching; other plays in the same playbook run with their own serial value or none. It is tempting because a playbook may contain several plays, but global behaviour would require setting serial on every play individually.
Go deeper
Related to this question
About these practice questions
One of 392 original EX294 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This EX294 practice question is part of Courseiva's free Red Hat 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 EX294 exam.