Install, Upgrade and Roll Back with Helm

Why this matters

Third-party software on Kubernetes ships as charts: databases, ingress controllers, monitoring stacks. Installing them by hand-copying manifests means owning upgrades forever. Helm owns the lifecycle instead: one release name, numbered revisions, values that separate your configuration from the chart author's templates.

Concepts

A chart is the package: templates plus default values plus metadata. A release is an installed instance: same chart installed twice with different names makes two independent releases. Values files override defaults without touching templates, which keeps upgrades clean: your choices live in your file, the chart stays upstream.

helm install <release> <chart> -f my-values.yaml creates revision 1. helm upgrade <release> <chart> -f my-values.yaml creates revision 2 with a three-way merge of old values, new values and live state. helm rollback <release> <revision> returns to any recorded revision. helm template renders manifests locally with no cluster contact: read before you install, always.

Namespaces matter: --create-namespace -n staging scopes the release, and deleting a namespace removes its releases with it. Values precedence (CLI --set beats files beat chart defaults) decides the final manifest; when output surprises you, check the precedence chain first.

Worked example

A demo database, configured, upgraded, retreated:

helm repo add bitnami https://charts.bitnami.com/bitnami
helm install demo-db bitnami/postgresql \
  -n demo --create-namespace \
  -f demo-values.yaml
helm list -n demo            # revision 1, deployed
helm template bitnami/postgresql -f demo-values.yaml | head -40
# change one value, upgrade, regret, retreat
helm upgrade demo-db bitnami/postgresql -n demo -f demo-values-v2.yaml
helm history demo-db -n demo
helm rollback demo-db 1 -n demo
helm status demo-db -n demo  # back on revision 1, deployed

History plus status is the receipt chain: every change numbered, every state named.

Exam notes

Forgetting -n installs into default and orphans the release from your mental model: always name the namespace. --set quoting bites with dots and commas in values: prefer files for anything complex. And rollback returns manifests, not data: a migrated database does not un-migrate, which no package manager can fix for you.