Easy everything in DevOps & Cloud, page 10
GitOps Principles: Your Repo as the Source of Truth
GitOps treats infrastructure state like code, with your Git repo as the single source of truth. Automated agents pull declarative configs from the repo to reconcile the live system, making it ideal for Kubernetes.
Kubernetes Events: The Cluster's Short-Term Memory
Think of Kubernetes Events as a cluster's temporary log, recording state changes like a Pod starting or a container failing. Use them with kubectl describe to debug issues in real-time.
The Three Pillars of Observability
Observability isn't one tool; it's a three-legged stool of metrics, logs, and traces. Metrics give the 'what' (CPU is high), logs the 'why' (an error loop), and traces the 'where' (which service is slow). The footgun is treating them as separate silos.
Kubernetes RBAC: Roles vs. ClusterRoles
Think of Kubernetes RBAC Roles as permissions for a single room (a Namespace), while ClusterRoles grant access to the entire building (the cluster). Use Roles for namespaced apps and ClusterRoles for admin tasks.
PersistentVolumeClaim: How Pods Request Storage
A PersistentVolumeClaim (PVC) is a request for storage, like a claim check for a storage locker. Pods use it to mount durable storage for databases or file uploads. The footgun: a PVC is just a request; a matching PersistentVolume must exist to fulfill it.
Kubernetes: Inject ConfigMaps & Secrets as Env Vars
Injecting ConfigMaps and Secrets as environment variables decouples your app from its configuration. Kubernetes passes these key-value pairs into your container at startup, perfect for things like API keys or feature flags.
Kubernetes Secrets: Managing Sensitive Data in Pods
A Kubernetes Secret is a dedicated object for storing sensitive data like API keys, separating them from your application code. It's used to inject database credentials or TLS certificates into pods.
Kubernetes DNS: How Pods Find Each Other
Kubernetes DNS gives services and pods stable, human-readable names so you don't have to track ephemeral IP addresses. It's how a frontend pod finds a backend service.
ClusterIP Service: Internal-Only Networking
A ClusterIP service is like an unlisted phone number for your pods, providing a stable internal IP for communication *within* the cluster. Use it for backend-to-backend traffic. The footgun is assuming it's reachable from the outside—it's not.
Imperative kubectl: Directly Command Your Cluster
Imperative kubectl is like giving direct orders to your cluster: 'run this,' 'scale that.' It's great for quick, one-off tasks like debugging a pod or handling an incident.
Recreate Deployment: Downtime for a Clean Slate
The Recreate strategy is like flipping a switch: it shuts down all old pods before starting new ones. This guarantees downtime but is necessary for breaking changes, like a database migration. The footgun is a failed deployment leaves you with no running app.
Kubernetes Jobs: For Tasks That Need to Finish
A Kubernetes Job runs a task to completion, unlike a Deployment which runs forever. Use it for one-off operations like database migrations or batch processing. The footgun is forgetting to set a retry limit, causing failed jobs to loop indefinitely.
Kubernetes Requests and Limits: Your Pod's Resource Contract
Kubernetes Requests and Limits are your pod's resource contract: requests guarantee a minimum for scheduling, while limits enforce a maximum at runtime. This prevents one greedy app from crashing others.
ReplicaSet: Kubernetes' Pod Thermostat
A ReplicaSet is Kubernetes' thermostat for pods, ensuring a specific number of replicas are always running. It replaces crashed pods or removes excess ones to maintain a stable state.
Labels and Selectors: The Glue of Kubernetes
Labels are key-value tags for organizing Kubernetes objects; selectors are queries to find them. This is how a Service finds its Pods. The main footgun is a mismatched selector, which orphans Pods from the Deployment that created them.
Kubernetes Pods: The Atomic Unit of Deployment
A Pod is the smallest deployable unit in Kubernetes, a wrapper for one or more containers that run together on one machine. It's used for tightly coupled 'sidecar' helpers, like a log shipper.
Docker Image Prune: Reclaim Your Disk Space
Docker image prune is a garbage collector for your local Docker setup, deleting unused images to free up disk space. Use it when low on storage after many builds. The footgun: by default, it only removes *dangling* (untagged) images, not all unused ones.
Docker Login: Authenticating to a Container Registry
docker login saves your credentials for a container registry, letting you push and pull private images. Use it before interacting with private repos on Docker Hub, ECR, or GCR. The footgun: credentials are often stored unencrypted by default.
Docker Push and Pull: Moving Container Images
Think of docker push and pull like git push and pull, but for container images. They move images between your machine and a remote registry. A common mistake is forgetting to tag an image with the registry's full address before pushing.
Docker Hub: The Central Repository for Containers
Think of Docker Hub as the GitHub for Docker images. It's a central repository from Docker, Inc. for finding, storing, and sharing pre-built software containers to automate code deployment.
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