Mixed Deck — All COA Topics Flashcards

Which OpenStack project provides DNS as a service with support for highly available DNS backends?

Answer: Designate

Designate is OpenStack's DNS-as-a-Service project that integrates with DNS backends like BIND and PowerDNS to provide zone and record management.

Which Heat resource type would you use to create a set of identically configured Nova instances that can scale horizontally?

Answer: OS::Heat::AutoScalingGroup

OS::Heat::AutoScalingGroup manages a collection of identical resources and integrates with Ceilometer/Aodh alarms for automatic scaling actions.

What is the 'OS::Heat::WaitCondition' resource used for in Heat templates?

Answer: To block stack completion until an application inside an instance signals readiness

OS::Heat::WaitCondition allows Heat to pause and wait for a signal (via a callback URL) from an instance, typically used to confirm that application bootstrapping has completed.

Why should automation scripts include version control?

Answer: To track changes, enable rollbacks, and support collaborative development

Version control tracks all changes, enables quick rollbacks if issues arise, and supports collaborative development with full change history.

What is a 'nested stack' in Heat orchestration?

Answer: A stack referenced as a resource within another template, enabling modular design

Nested stacks allow a template to reference another template as a resource type, enabling modular, reusable infrastructure components.

When designing an OpenStack deployment for maximum resiliency, which of the following best describes the purpose of using multiple availability zones?

Answer: To isolate failure domains so a single hardware failure does not affect all instances

Availability zones isolate failure domains — a power outage or hardware failure in one zone should not impact instances running in another zone.

Which Cinder option configures the minimum free space percentage that must remain on a storage backend before it stops accepting new volumes?

Answer: reserved_percentage

reserved_percentage tells Cinder to keep that fraction of backend capacity free and report it as unavailable for scheduling.

Which file must be modified on a Nova compute node to enable encrypted inter-instance communication using QEMU's built-in encryption?

Answer: /etc/nova/nova.conf with libvirt encryption settings

Nova's nova.conf under the [libvirt] section contains settings to configure encrypted storage and communication options for QEMU/KVM instances.

Which OpenStack CLI command lists all available Heat template versions?

Answer: openstack orchestration template version list

The 'openstack orchestration template version list' command displays all HOT and CFN template versions supported by the Heat service.

What is the difference between monitoring and observability?

Answer: Monitoring tracks known metrics while observability enables investigation of unknown issues

Monitoring tracks predefined metrics, while observability provides the tooling and data to investigate unexpected or unknown issues through logs, traces, and metrics.

Which Nova configuration option allows CPU overcommit ratios to be set, enabling more vCPUs than physical cores on a host?

Answer: cpu_allocation_ratio

cpu_allocation_ratio multiplies reported physical CPUs by the given factor, allowing Nova to schedule more vCPUs than physically available.

Which component provides a web-based user interface for OpenStack?

Answer: Horizon

Horizon is the official web-based dashboard for OpenStack, providing a graphical user interface (GUI) for users and administrators. It allows for easy management of OpenStack resources such as instances, images, networks, and volumes through a web browser, simplifying cloud operations.

Which intrinsic function in HOT is used to reference the value of a parameter defined in the same template?

Answer: get_param

The 'get_param' intrinsic function retrieves the value of a parameter defined in the 'parameters' section of the template.

Which Nova feature allows an administrator to isolate specific compute hosts so that only designated tenants can schedule instances on them?

Answer: Host aggregates with metadata filters

Host aggregates with AggregateInstanceExtraSpecsFilter allow administrators to restrict instance scheduling to specific hosts based on tenant metadata.

Which Nova policy action controls whether a user can list all instances across all tenants (not just their own)?

Answer: os_compute_api:servers:detail:get_all_tenants

The 'get_all_tenants' policy governs whether a user can retrieve server listings belonging to all projects.

What does 'stack rollback' do in OpenStack Heat?

Answer: Automatically deletes a stack if its creation fails, restoring the prior state

When rollback is enabled and a stack creation fails, Heat automatically deletes the partially created stack to avoid leaving orphaned resources.

What does the 'openstack metric resource list' command display?

Answer: All resources tracked in Gnocchi with their associated metrics

The 'openstack metric resource list' command shows all resources registered in Gnocchi along with the metrics associated with each.

A cloud operator needs to ensure that all object storage data at rest is encrypted. Which Swift configuration enables this?

Answer: Swift encryption middleware (keymaster + encrypter)

Swift's encryption middleware pipeline (keymaster for key derivation + encrypter for data encryption) provides transparent at-rest encryption.

What does the `openstack token issue` command generate?

Answer: A temporary Keystone authentication token for the current session

`openstack token issue` generates a time-limited Keystone token that authenticates API requests without repeatedly submitting user credentials.

What is the purpose of the 'ceilometer-agent-notification' service?

Answer: It listens to the OpenStack message bus for notifications and converts them into Ceilometer samples

The ceilometer-agent-notification service subscribes to the OpenStack message bus and transforms notification events from services like Nova and Cinder into Ceilometer samples.