JNCIA-DevOps flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Idempotent automation

A property where running the same task repeatedly yields the identical end state without extra side effects, so re-runs are safe and configuration drift is avoided.

Junos PyEZ Device object

The core PyEZ class opened with Device(host, user, password) that represents a Junos device session and exposes rpc, cli, and Config capabilities.

PyEZ Config commit sequence

Lock the candidate, load the configuration, run commit_check, then commit, then unlock. This prevents concurrent edits and validates before applying.

commit confirmed

A Junos commit that automatically rolls back after a timer unless a confirming commit is issued, protecting remote changes from locking you out.

YAML indentation rule

YAML uses spaces, never tabs, and nested mappings are indented consistently, typically two spaces per level; list items begin with a hyphen and space.

Junos REST API call

An HTTPS request to the device, such as POST /rpc with a JSON body and basic authentication, returning JSON or XML results for the requested operation.

Ansible junos_config module

An Ansible module that pushes configuration lines to a Junos device over NETCONF or CLI, supporting commit confirmation and rollback on failure.

DORA four metrics

Deployment frequency, lead time for changes, change failure rate, and time to restore service are the four metrics used to measure software delivery performance.

Continuous integration

A practice where developers merge changes frequently and each merge triggers automated build and test, catching integration defects early.

Continuous delivery vs deployment

Continuous delivery keeps every change releasable with a manual approval gate; continuous deployment removes the gate and releases automatically.

Blameless postmortem

A review after an incident that examines systemic and process causes rather than blaming individuals, producing documented corrective actions.

Shift left

Moving testing, security scanning, and validation earlier in the development lifecycle so defects are found sooner and cost less to fix.

Configuration drift

Divergence between the declared desired state in code and the actual running state on devices, detected by compliance checks and corrected by idempotent tooling.

Git pull request flow

Create a feature branch, commit changes locally, push to the remote, open a pull request for review, then merge into the main branch.

Declarative versus imperative IaC

Declarative IaC states the desired end result and lets the tool decide steps; imperative IaC lists explicit commands to execute in order.

Terraform state file

A file mapping declared resources to real infrastructure objects; storing it remotely with locking prevents concurrent applies from corrupting it.

Ansible playbook structure

A YAML document listing target hosts, optional privileges, and an ordered list of tasks, each naming a module with its arguments.

Ansible variable precedence

Variables can come from inventory, group_vars, host_vars, play vars, and extra vars; extra vars passed with -e take highest precedence.

Junos configuration hierarchy

Junos configuration is a tree of statements such as system, interfaces, and protocols; set commands are converted into that tree at commit time.

Junos apply-groups

A statement that applies a named configuration group's shared settings to a hierarchy level, reducing duplication across interfaces or routing instances.

Jinja2 template syntax

Templates use double braces for variable substitution, brace-percent for loops and conditionals, and are rendered by Ansible's template module.

PyEZ Table and View

A Table defines the RPC and fields to retrieve operational data, and a View maps returned XML elements to Python object attributes.

CI pipeline stages

Typical ordered stages are source checkout, lint, unit test, build, deploy to staging, integration test, and deploy to production.

Fail fast in CI

A pipeline stops at the first stage returning a non-zero exit status and reports failure, avoiding wasted work on later stages.

Build artifact promotion

The practice of building an artifact once and moving the same artifact through staging and production environments rather than rebuilding each time.

Blue-green deployment

Two identical environments run in parallel; traffic switches to the new version after validation, and rollback means switching back.

Canary deployment

A release strategy that routes a small percentage of traffic to the new version, monitors health, then gradually increases exposure.

Pipeline as code

Storing the CI/CD pipeline definition as a versioned file in the repository so builds are reviewable, reproducible, and consistent.

Junos NETCONF port

NETCONF on Junos runs over SSH on TCP port 830 and is enabled with the system services netconf ssh configuration statement.

NETCONF edit-config

An operation that loads configuration changes into the candidate datastore; a separate commit operation applies them to the running configuration.

Junos REST endpoints

The REST API exposes /rpc for operational RPCs and /config for configuration, using HTTP GET, POST, PUT, and DELETE methods.

Junos commit script

An on-box script that runs before a commit completes and can inspect or modify the candidate configuration, enforcing policy automatically.