kubectl patch: Command Reference for CI/CD

Surgically update one field from a script: pick the right patch type.

kubectl patch applies a partial update and is the scriptable alternative to edit. Choosing the correct --type is what makes it behave as expected. This reference compares the three patch types and shows a CI example.

Common flags and usage

--type=strategic (default): Kubernetes list-aware merge for core types
--type=merge: plain RFC 7386 merge; replaces lists wholesale (use for CRDs)
--type=json: RFC 6902 op list (add/replace/remove) at explicit paths
-p '<patch>': inline patch body
--patch-file <file>: read the patch from a file

Example

shell

kubectl patch deploy/web --type=json \
  -p '[{"op":"replace","path":"/spec/replicas","value":4}]'

kubectl patch svc/web --type=merge \
  -p '{"spec":{"type":"LoadBalancer"}}'

In CI

Strategic-merge patches misbehave on custom resources, which lack merge metadata, so use --type=merge or --type=json for CRDs. A JSON-patch op against a path that does not exist fails server-side; add the parent first. Prefer apply for whole-object declarative changes and patch only for narrow, scripted edits.

Key takeaways

Wrong --type is the top patch mistake; CRDs need merge or json.
json patches edit explicit paths; the path must already exist for replace.
For whole-object declarative changes, prefer apply over patch.

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