Glossary

Plain-language definitions for everything used in this guide. Future-you will thank present-you. Terms are alphabetical.

ACME

The protocol Let’s Encrypt uses to issue TLS certificates automatically. The server proves it controls a domain (see HTTP-01), and gets a cert in return.

AnalysisTemplate

An Argo Rollouts resource that queries a metric to pass or fail a canary. Not installed on this platform yet. Canaries are time pauses only.

Approved sender

An address OCI Email Delivery lets an app send from (<app>@mail.visarend.systems). It lives in a compartment, and only groups allowed to use approved-senders there can send as it. See Email.

Argo CD

The controller that watches a Git repo and continuously makes the cluster match it (see Reconcile). If Git and the cluster differ, Argo CD applies the difference.

Argo Rollouts

A controller that replaces a plain Kubernetes Deployment with smarter rollout strategies. Here, a canary that shifts traffic gradually (here: timed steps; metric gates later).

barman / barman-cloud

The backup tool CNPG uses to push Postgres base backups and WAL to object storage (S3-compatible).

Canary

A deployment strategy: send a small slice of traffic to the new version first, wait, then ramp up. This platform pauses on a timer. Metric auto-abort is not installed yet.

cert-manager

A Kubernetes controller that obtains and auto-renews TLS certificates (from Let’s Encrypt) and stores them as Secrets for Traefik to serve.

CNPG

CloudNativePG: the Postgres operator. You declare a Cluster resource; CNPG provisions and manages the actual Postgres pods, failover, backups, and a connection Secret.

CR / CRD

Custom Resource: a Kubernetes object type added by an operator (e.g. a CNPG Cluster, a Keycloak Keycloak). CRD = Custom Resource Definition, the schema that registers that new type.

DKIM

DomainKeys Identified Mail. The sending service signs each email with a key whose public half is published in DNS (here a CNAME under _domainkey.mail), so receivers can check the mail really came from the domain.

DMARC

A DNS policy (_dmarc.mail) telling receivers what to do with mail that fails SPF and DKIM checks, and where to send reports. p=none only reports.

DNAT

Destination NAT. A firewall (iptables) rule that rewrites a packet’s destination. k3s’s ServiceLB uses it to grab host ports 80/443, which can silently bypass other host services.

FGAP

Fine-Grained Admin Permissions. Keycloak’s newer (26.2+) authorization model for its own Admin API. Explains why classic realm-management client roles didn’t behave as expected setting up keycloak-config-cli; the working grant is the composite admin realm role, not individual client roles.

GHCR

GitHub Container Registry (ghcr.io). Where CI publishes the app’s container images for the cluster to pull.

Helm

A package manager for Kubernetes (installs apps as versioned “charts”). Used here to bootstrap the platform layer (cert-manager, Argo). See Provision.

HTTP-01

An ACME challenge type: Let’s Encrypt verifies you own a domain by fetching a token from http://<domain>/.well-known/... on port 80. Needs public DNS + port 80 open.

Infisical

A self-hosted, GUI-managed secrets manager. You edit an app’s env vars. Secret or not. In a browser; the Infisical Secrets Operator syncs them into a plain Kubernetes Secret the app already reads. See Secrets.

Ingress

A Kubernetes object that maps a hostname/path to a Service. Traefik reads Ingress objects and routes external traffic accordingly.

k3s

A lightweight, single-binary Kubernetes distribution. Ideal for one small node. Bundles Traefik and a load balancer.

Keycloak

The identity provider (auth server). Issues tokens to apps via OIDC/PKCE; apps validate those tokens. Runs in-cluster, managed by its operator.

keycloak-config-cli

A Sync-hook Job that patches workloads/keycloak/overlays/<env>/realms/*.yaml into live Keycloak incrementally via the Admin API. An update-capable alternative to the Keycloak Operator’s create-only KeycloakRealmImport CRD. Authenticates as its own non-expiring service account, not a human admin. See Example: Keycloak.

kubectl

The command-line tool for talking to the Kubernetes API (inspect/apply/delete resources).

Machine Identity

Infisical’s term for a non-human credential (Universal Auth: a Client ID + Client Secret) that a service (here, the Infisical Secrets Operator) authenticates as, scoped to one project/environment.

Namespace

A virtual partition inside a cluster that isolates a group of resources (e.g. the <app>-staging namespace holds that env’s pods, Postgres, and Secrets).

OCI Email Delivery

Oracle Cloud’s outbound email service. Apps and Keycloak send through its SMTP endpoint on port 587 with per-app credentials. See Email.

OIDC

OpenID Connect. The identity layer on top of OAuth2 that Keycloak speaks. Apps get a signed token proving who the user is.

Operator

Software that extends Kubernetes to manage a complex app for you: you declare a CR (“I want a Postgres cluster”), the operator does the work and keeps it healthy. Think “robot DBA/admin.”

PITR

Point-In-Time Recovery. Restoring a database to any moment within a retention window, by replaying WAL on top of a base backup.

PKCE

Proof Key for Code Exchange. The secure OAuth2 flow for browser apps (no client secret in the browser). The web app uses it to log in against Keycloak.

Prometheus

Metrics database. Not installed here yet. When added, it would scrape /metrics and could gate canaries.

Reconcile

The continuous loop where a controller compares desired state (Git) to actual state (cluster) and applies the difference. This declarative, Git-driven approach is the core idea behind the whole platform: you change infrastructure by committing YAML, not by running kubectl commands by hand.

Secret (Kubernetes)

An object holding sensitive data (passwords, keys). Referenced by pods at runtime. Rule here: secret values never live in Git. They’re created out-of-band or sealed.

ServiceLB (klipper)

k3s’s built-in load balancer (its internal name is “klipper”). It claims host ports 80/443 (via DNAT) and forwards them to Traefik. (Cause of a classic “who owns port 443?” gotcha.)

SigV4

AWS Signature Version 4. How S3 (and S3-compatible stores like Oracle) authenticate requests. Sensitive to correct keys and region.

SPF

Sender Policy Framework. A DNS TXT record listing which servers may send mail for a domain. mail.visarend.systems’s record names OCI’s; the mailbox provider’s record on visarend.systems is separate.

TLS

Transport Layer Security. The encryption behind HTTPS. cert-manager obtains the certs; Traefik terminates TLS at the edge.

Traefik

The reverse proxy / Ingress controller bundled with k3s. The platform’s single “front door”: it terminates TLS and routes every hostname to the right Service.

WAL

Write-Ahead Log. Postgres’s stream of every change. Archiving it continuously enables PITR: replay the WAL to reach any point in time.