What is KubeLinter?
KubeLinter analyzes Kubernetes YAML files, Helm charts, and Kustomize manifests, and checks them against a variety of best practices, with a focus on production readiness and security.
KubeLinter runs sensible default checks, designed to give you useful information about your Kubernetes YAML files, Helm charts, and Kustomize manifests. This is to help teams check early and often for security misconfigurations and DevOps best practices. Some common examples of these include running containers as a non-root user, enforcing least privilege, and storing sensitive information only in secrets.
KubeLinter is configurable, so you can enable and disable checks, as well as create your own custom checks, depending on the policies you want to follow within your organization.
When a lint check fails, KubeLinter reports recommendations for how to resolve any potential issues and returns a non-zero exit code.
Documentation
Visit https://docs.kubelinter.io for detailed documentation on installing, using and configuring KubeLinter.
Installing KubeLinter
Kube-linter binaries could be found here: https://github.com/stackrox/kube-linter/releases/latest
Using Go
To install using Go, run the following command:
go install golang.stackrox.io/kube-linter/cmd/kube-linter@latest
Otherwise, download the latest binary from Releases and add it to your
PATH.
Using Homebrew for macOS or LinuxBrew for Linux
To install using Homebrew or LinuxBrew, run the following command:
brew install kube-linter
Using nix-shell
nix-shell -p kube-linter
Using docker
docker pull stackrox/kube-linter:latest
Development
Prerequisites
- Make sure that you have installed Go prior to building from source.
Building KubeLinter
Installing KubeLinter from source is as simple as following these steps:
-
First, clone the KubeLinter repository.
git clone [email protected]:stackrox/kube-linter.git
-
Then, compile the source code. This will create the kube-linter binary files for each platform and places them in the .gobin folder.
make build
-
Finally, you are ready to start using KubeLinter. Verify your version to ensure you've successfully installed KubeLinter.
.gobin/kube-linter version
Testing KubeLinter
There are several layers of testing. Each layer is expected to pass.
-
go unit tests:
make test
-
end-to-end integration tests:
make e2e-test
-
and finally, end-to-end integration tests using bats-core:
make e2e-bats
Verifying KubeLinter images
KubeLinter images are signed by cosign.
We recommend verifying the image before using it.
Once you've installed cosign, you can use the KubeLinter public key to verify the KubeLinter image with:
cat kubelinter-cosign.pub
-----BEGIN PUBLIC KEY-----
MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEl0HCkCRzYv0qH5QiazoXeXe2qwFX
DmAszeH26g1s3OSsG/focPWkN88wEKQ5eiE95v+Z2snUQPl/mjPdvqpyjA==
-----END PUBLIC KEY-----
cosign verify --key kubelinter-cosign $IMAGE_NAME
KubeLinter also provides cosign keyless signatures.
You can verify the KubeLinter image with:
# NOTE: Keyless signatures are NOT PRODUCTION ready.
COSIGN_EXPERIMENTAL=1 cosign verify $IMAGE_NAME
Using KubeLinter
Local YAML Linting
Running KubeLinter to Lint your YAML files only requires two steps in its most basic form.
-
Locate the YAML file you'd like to test for security and production readiness best practices:
-
Run the following command:
kube-linter lint /path/to/your/yaml.yaml
Example
Consider the following sample pod specification file pod.yaml. This file has two production readiness issues and one security issue:
Security Issue:
- The container in this pod is not running as a read only file system, which could allow it to write to the root filesystem.
Production readiness:
-
The container's memory limits are not set, which could allow it to consume excessive memory
apiVersion: v1
kind: Pod
metadata:
name: security-context-demo
spec:
securityContext:
runAsUser: 1000
runAsGroup: 3000
fsGroup: 2000
volumes:
- name: sec-ctx-vol
emptyDir: {}
containers:
- name: sec-ctx-demo
image: busybox
resources:
requests:
memory: "64Mi"
cpu: "250m"
command: [ "sh", "-c", "sleep 1h" ]
volumeMounts:
- name: sec-ctx-vol
mountPath: /data/demo
securityContext:
allowPrivilegeEscalation: false
-
Copy the YAML above to pod.yaml and lint this file by running the following command:
kube-linter lint pod.yaml
-
KubeLinter runs its default checks and reports recommendations. Below is the output from our previous command.
pod.yaml: (object: <no namespace>/security-context-demo /v1, Kind=Pod) The container "sec-ctx-demo" is using an invalid container image, "busybox". Please use images that are not blocked by the `BlockList` criteria : [".*:(latest)$" "^[^:]*$" "(.*/[^:]+)$"] (check: latest-tag, remediation: Use a container image with a specific tag other than latest.)
pod.yaml: (object: <no namespace>/security-context-demo /v1, Kind=Pod) container "sec-ctx-demo" does not have a read-only root file system (check: no-read-only-root-fs, remediation: Set readOnlyRootFilesystem to true in the container securityContext.)
pod.yaml: (object: <no namespace>/security-context-demo /v1, Kind=Pod) container "sec-ctx-demo" has memory limit 0 (check: unset-memory-requirements, remediation: Set memory limits for your container based on its requirements. Refer to https://kubernetes.io/docs/concepts/configuration/manage-resources-containers/#requests-and-limits for details.)
Error: found 3 lint errors
Multiple Output Formats
KubeLinter supports generating multiple output formats in a single run. This is useful for generating both human-readable and machine-readable reports simultaneously:
kube-linter lint \
--format sarif --output kube-linter.sarif \
--format json --output kube-linter.json \
--config .kube-linter.yaml \
pod.yaml
This command will:
- Generate a SARIF format report in
kube-linter.sarif
- Generate a JSON format report in
kube-linter.json
- Process the files only once, improving efficiency
Note: Multiple formats require explicit --output flags. For single format output to stdout, use just one --format flag without --output.
For more details on using multiple output formats, see the documentation.
To learn more about using and configuring KubeLinter, visit the documentation page.
Mentions/Tutorials
The following are tutorials on KubeLinter written by users. If you have one that you would like to add to this list, please send a PR!
LICENSE
KubeLinter is licensed under the Apache License 2.0.
Community
If you would like to engage with the KubeLinter community, including maintainers and other users, you can join the Slack workspace here.
There may be breaking changes in the future to the command usage, flags, and configuration
file formats. However, we encourage you to use KubeLinter to test your environment YAML
files, see what breaks, and contribute.
As a reminder, all participation in the KubeLinter community is governed by our
code of conduct.
KubeLinter is created with ❤️ by StackRox and is now powered
by Red Hat.
