LPI DevOps Tools Engineer flashcards

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

Git index

The staging area holding a snapshot of changes selected for the next commit; `git add` writes to it and `git commit` records it as a tree object.

Fast-forward merge

A merge where the target branch has no new commits, so Git simply moves the branch pointer forward without creating a merge commit.

Semantic versioning

A versioning scheme MAJOR.MINOR.PATCH where MAJOR signals breaking changes, MINOR backward-compatible features, and PATCH backward-compatible bug fixes.

Git bisect

A binary-search command over commit history that marks commits good or bad to identify the first commit introducing a defect.

Twelve-Factor config

The principle that configuration is stored in environment variables, separated from code, so the same build artifact runs unchanged across environments.

CI pipeline gating

Each stage (build, test, package, deploy) runs only if the previous stage exits successfully, preventing defective artifacts from progressing.

Infrastructure as Code

Managing infrastructure through machine-readable definition files that tools apply to reach a declared state, enabling versioning and repeatable provisioning.

Git commit object

An immutable object containing a tree hash, parent commit hashes, author and committer metadata, and a message; its SHA identifies the commit.

Linux namespaces

Kernel features isolating PID, network, mount, UTS, IPC, and user views; containers rely on them to present an isolated environment sharing the host kernel.

cgroups

Linux control groups that limit and account for CPU, memory, and I/O consumption of processes, forming the resource boundary for containers.

Docker layer cache

Each Dockerfile instruction creates a layer; when an instruction or its parent layer changes, that layer and all later layers rebuild.

Multi-stage build

A Dockerfile using several FROM stages so build tools stay in intermediate stages and only required artifacts are copied into the final image.

COPY versus ADD

COPY copies files from the build context; ADD also fetches URLs and extracts local tar archives, so COPY is preferred for predictable behavior.

Image tag default

When no tag is given in an image reference, Docker uses `latest`; because it is mutable, pinning explicit tags or digests is needed for reproducibility.

Build context

The directory sent to the Docker daemon at build start; `.dockerignore` excludes files from it and from COPY instructions, reducing transfer size.

PID 1 in container

The first process in a container must reap orphaned child processes and handle SIGTERM; an init such as tini supplies this behavior.

Port publishing

`docker run -p hostPort:containerPort` maps a host port to a container port, making the service reachable from outside the container network.

kube-apiserver

The control-plane component that exposes the Kubernetes API, validates requests, and is the only component that talks directly to etcd.

etcd

A distributed key-value store holding all Kubernetes cluster state; losing it without backup means losing the cluster's desired and observed configuration.

kube-scheduler

The control-plane component that assigns newly created pods to nodes based on resource requests, affinity rules, taints, and tolerations.

kubelet

The node agent that watches the API server for pods assigned to its node and ensures their containers run and report status.

ClusterIP Service

The default Service type, allocating a virtual IP reachable only inside the cluster; kube-proxy programs routing rules for it on each node.

StatefulSet

A workload controller giving pods stable ordinal names, stable network identities, and per-pod PersistentVolumeClaims, suited to databases and clustered apps.

Readiness probe

A probe whose failure removes the pod from Service endpoints without restarting it, preventing traffic to containers not yet able to serve.

Liveness probe

A probe whose repeated failure causes kubelet to restart the container, used to recover from deadlocks and unrecoverable process states.

Resource requests and limits

Requests determine scheduling by reserving node capacity; limits cap runtime usage, and exceeding a memory limit causes the container to be OOMKilled.

DaemonSet

A controller ensuring one pod runs on every eligible node, commonly used for log shippers, monitoring agents, and network plugins.

Observability pillars

Metrics are numeric aggregates over time, logs are discrete timestamped events, and traces record a request's path across services with span timing.

Four golden signals

Latency, traffic, errors, and saturation form a minimal metric set for monitoring a user-facing service and detecting degradation.

Prometheus pull model

Prometheus scrapes HTTP `/metrics` endpoints on a schedule and stores time series; exporters expose metrics for systems that cannot emit them natively.

Kubernetes RBAC

Role and RoleBinding grant namespaced permissions; ClusterRole and ClusterRoleBinding are cluster-wide; rules are additive and default-deny.

Pod Security Standards

Three built-in profiles - privileged, baseline, and restricted - that constrain pod fields such as user IDs, capabilities, and host access.