KuberneteskubectlIntermediate~4h

Kubernetes: Config & Networking

What the container actually sees

A Pod is restarting and the manifest looks right. Almost every one of those mornings is settled by four lines nobody read: a value that never arrived, a name completed with the wrong namespace, a rule that matched something else, or a probe that killed a slow program. This is that reading, drilled until it is fast.

Start this project See the modules

Modules: 6
Drills: 13
Build steps: 2
Time: ~4h

Walk out able to

Take a Pod you have never seen, say what it was handed and what it can find — and when it is looping instead of serving, name the one thing that is wrong.

What you drill

Config and secrets

Which value wins, what an edit reaches, who can read it.

Names inside the cluster

What a short name reaches, and what it costs in lookups.

Traffic from outside

Which backend a rule picks, and why an Ingress is inert.

Probes and crash loops

Which probe restarts, which removes, and what killed it.

The pitch

What you practise, and what you leave with

Not an artifact — a diagnosis. Thirteen skills on manifests that never repeat, plus a crash loop you cause yourself and read the evidence off.

You will practise

Config and Secret fields, and what an edit reaches
Cluster DNS, search domains and lookup cost
Ingress hosts, paths and why one is inert
Liveness, readiness, startup and the crash loop

Afterwards you can

Say which value a container starts with
Say what a name reaches, and what it costs
Name which probe restarts and which removes
Diagnose a crash loop from four lines

Modules

6 modules, 27 items

Lessons explain one idea. Drills repeat it until it sticks. Build steps make something that exists afterwards.

1
Hand it its configuration
~40 min
Say which value the container starts with, and what an edit to the ConfigMap reaches.
- LessonWhat the container actually sees5 min
- LessonName the four ways a value gets in8 min
- LessonSettle a duplicate name6 min
- DrillName the value the container gets10 min
- DrillSay what a config edit reaches11 min
2
Secrets, and what they are not
~45 min
Say who can read a credential and by which route, and write the references from memory.
- LessonWeigh what a Secret protects8 min
- LessonChoose a file or a variable6 min
- DrillSay who ends up holding it11 min
- Build stepUndo a Secret in one command8 min
- DrillWrite the reference from memory12 min
3
Find it by name
~33 min
Say what a cluster-local address reaches, and how many lookups the name costs.
- LessonComplete a short name yourself7 min
- LessonCount what a short name costs7 min
- DrillSay what the address reaches10 min
- DrillCount the lookups it costs9 min
4
Let the outside in
~36 min
Apply the host and path rules, and name why an Ingress is doing nothing at all.
- LessonRoute one request by hand8 min
- LessonSay what an Ingress needs first7 min
- DrillPick the backend the rules choose11 min
- DrillName why the Ingress does nothing10 min
5
Two probes, two different jobs
~34 min
Say which probe removes an endpoint and which restarts a container, and what each buys.
- LessonSeparate restarting from removing8 min
- LessonSpot the crash loop a probe caused7 min
- DrillSay what a failing probe does10 min
- DrillWork out what the probe buys9 min
6
Debug a CrashLoopBackOff
~1h
Name the state, find the cause in the evidence, and say when it will try again.
- DrillName the reason it is not running10 min
- DrillFind what killed the container13 min
- DrillWork out when it tries again9 min
- Build stepBreak a Pod on purpose20 min
- LessonDiagnose an incident cold16 min