Popeye: Kubernetes Live Cluster Linter

Popeye is a utility that scans live Kubernetes clusters and reports potential issues with deployed resources and configurations. As Kubernetes landscapes grows, it is becoming a challenge for a human to track the slew of manifests and policies that orchestrate a cluster. Popeye scans your cluster based on what’s deployed and not what’s sitting on disk. By linting your cluster, it detects misconfigurations, stale resources and assists you to ensure that best practices are in place, thus preventing future headaches. It aims at reducing the cognitive overload one faces when operating a Kubernetes cluster in the wild. Furthermore, if your cluster employs a metric-server, it reports potential resources over/under allocations and attempts to warn you should your cluster run out of capacity.

Popeye is a readonly tool, it does not alter any of your Kubernetes resources in any way!

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You can dump the scan report to HTML.

Grafana Dashboard

Popeye publishes Prometheus metrics. We provided a sample Popeye dashboard to get you started in this repo.


Popeye is available on Linux, OSX and Windows platforms.

PreFlight Checks

The Command Line

You can use Popeye wide open or using a spinach yaml config to tune your linters. Details about the Popeye configuration file are below.

# Dump version info and logs location
popeye version
# Popeye a cluster using your current kubeconfig environment.
# NOTE! This will run Popeye in the context namespace if set or like kubectl will use the default namespace
# Run Popeye in the `fred` namespace
popeye -n fred
# Run Popeye in all namespaces
popeye -A
# Popeye uses a spinach config file of course! aka spinachyaml!
popeye -f spinach.yaml
# Popeye a cluster using a kubeconfig context.
popeye --context olive
# Stuck?
popeye help


Popeye scans your cluster for best practices and potential issues. Currently, Popeye only looks for a given set of curated Kubernetes resources. More will come soon! We are hoping Kubernetes friends will pitch’in to make Popeye even better.

The aim of the linters is to pick up on misconfigurations, i.e. things like port mismatches, dead or unused resources, metrics utilization, probes, container images, RBAC rules, naked resources, etc…

Popeye is not another static analysis tool. It runs and inspect Kubernetes resources on live clusters and lint resources as they are in the wild!

Here is a list of some of the available linters:

  Resource Linters Aliases
🛀 Node   no
    Conditions ie not ready, out of mem/disk, network, pids, etc  
    Pod tolerations referencing node taints  
    CPU/MEM utilization metrics, trips if over limits (default 80% CPU/MEM)  
🛀 Namespace   ns
    Dead namespaces  
🛀 Pod   po
    Pod status  
    Containers statuses  
    ServiceAccount presence  
    CPU/MEM on containers over a set CPU/MEM limit (default 80% CPU/MEM)  
    Container image with no tags  
    Container image using latest tag  
    Resources request/limits presence  
    Probes liveness/readiness presence  
    Named ports and their references  
🛀 Service   svc
    Endpoints presence  
    Matching pods labels  
    Named ports and their references  
🛀 ServiceAccount   sa
    Unused, detects potentially unused SAs  
🛀 Secrets   sec
    Unused, detects potentially unused secrets or associated keys  
🛀 ConfigMap   cm
    Unused, detects potentially unused cm or associated keys  
🛀 Deployment   dp, deploy
    Unused, pod template validation, resource utilization  
🛀 StatefulSet   sts
    Unused, pod template validation, resource utilization  
🛀 DaemonSet   ds
    Unused, pod template validation, resource utilization  
🛀 PersistentVolume   pv
    Unused, check volume bound or volume error  
🛀 PersistentVolumeClaim   pvc
    Unused, check bounded or volume mount error  
🛀 HorizontalPodAutoscaler   hpa
    Unused, Utilization, Max burst checks  
🛀 PodDisruptionBudget    
    Unused, Check minAvailable configuration pdb
🛀 ClusterRole    
    Unused cr
🛀 ClusterRoleBinding    
    Unused crb
🛀 Role    
    Unused ro
🛀 RoleBinding    
    Unused rb
🛀 Ingress    
    Valid ing
🛀 NetworkPolicy    
    Valid, Stale, Guarded np
🛀 PodSecurityPolicy    
    Valid psp
🛀 Cronjob    
    Valid, Suspended, Runs cj
🛀 Job    
    Pod checks job
🛀 GatewayClass    
    Valid, Unused gwc
🛀 Gateway    
    Valid, Unused gw
🛀 HTTPRoute    
    Valid, Unused gwr

You can also see the full list of codes

Saving Scans

To save the Popeye report to a file pass the --save flag to the command. By default it will create a tmp directory and will store your scan report there. The path of the tmp directory will be printed out on STDOUT. If you have the need to specify the output directory for the report, you can use this environment variable POPEYE_REPORT_DIR. By default, the name of the output file follow the following format : lint_<cluster-name>_<time-UnixNano>.<output-extension> (e.g. : “lint-mycluster-1594019782530851873.html”). If you want to also specify the output file name for the report, you can pass the --output-file flag with the filename you want as parameter.

Example to save report in working directory:

POPEYE_REPORT_DIR=$(pwd) popeye --save

Example to save report in working directory in HTML format under the name “report.html” :

POPEYE_REPORT_DIR=$(pwd) popeye --save --out html --output-file report.html

Save To S3

Alternatively, you can push the generated reports to an AWS S3 bucket (or other S3 compatible Object Storage) by providing the flag --s3-bucket. For parameters you need to provide the name of the S3 bucket where you want to store the report. To save the report in a bucket subdirectory provide the bucket parameter as bucket/path/to/report.

The AWS Go lib is used which handles your credentials. For more information check out the official documentation.

Example to save report to S3:

popeye --s3-bucket=NAME-OF-YOUR-S3-BUCKET/OPTIONAL/SUBDIRECTORY --out=json

If AWS S3 is not your bag, you can further define an S3 compatible storage (OVHcloud Object Storage, Minio, Google cloud storage, etc…) using s3-endpoint and s3-region as so:


Docker Support

You can also run Popeye in a container by running it directly from the official docker repo on DockerHub. The default command when you run the docker container is popeye, so you customize the scan by using the supported cli flags. To access your clusters, map your local kubeconfig directory into the container with -v :

docker run --rm -it -v $HOME/.kube:/root/.kube derailed/popeye --context foo -n bar

Running the above docker command with --rm means that the container gets deleted when Popeye exits. When you use --save, it will write it to /tmp in the container and then delete the container when popeye exits, which means you lose the output ;( To get around this, map /tmp to the container’s /tmp.

NOTE: You can override the default output directory location by setting POPEYE_REPORT_DIR env variable.

docker run --rm -it \
  -v $HOME/.kube:/root/.kube \
  -e POPEYE_REPORT_DIR=/tmp/popeye \
  -v /tmp:/tmp \
  derailed/popeye --context foo -n bar --save --output-file my_report.txt

# Docker has exited, and the container has been deleted, but the file
# is in your /tmp directory because you mapped it into the container
cat /tmp/popeye/my_report.txt

Output Formats

Popeye can generate linter reports in a variety of formats. You can use the -o cli option and pick your poison from there.

Format Description Default Credits
standard The full monty output iconized and colorized yes  
jurassic No icons or color like it’s 1979    
yaml As YAML    
html As HTML    
json As JSON    
junit For the Java melancholic    
prometheus Dumps report a prometheus metrics   dardanel
score Returns a single cluster linter score value (0-100)   kabute

The Prom Queen!

Popeye can publish Prometheus metrics directly from a scan. You will need to have access to a prometheus pushgateway and credentials.

NOTE! These are subject to change based on users feedback and usage!!

In order to publish metrics, additional cli args must be present.

# Run popeye using console output and push prom metrics.
popeye --push-gtwy-url http://localhost:9091

# Run popeye using a saved html output and push prom metrics.
# NOTE! When scan are dump to disk, popeye_cluster_score metric below includes
# an additional label to track the persisted artifact so you can aggregate with the scan
# Don't think it's the correct approach as this changes the metric cardinality on every push.
# Hence open for suggestions here??
popeye -o html --save --push-gtwy-url http://localhost:9091

PopProm metrics

The following Popeye prometheus metrics are published:


A sample Grafana dashboard can be found in this repo to get you started.

NOTE! Work in progress, please feel free to contribute if you have UX/grafana/promql chops.


A spinach YAML configuration file can be specified via the -f option to further configure the linters. This file may specify the container utilization threshold and specific linter configurations as well as resources and codes that will be excluded from the linter.

NOTE! This file will change as Popeye matures!

Under the excludes key you can configure to skip certain resources, or linter codes. Popeye’s linters are named after the k8s resource names. For example the PodDisruptionBudget linter is named poddisruptionbudgets and scans policy/v1/poddisruptionbudgets

NOTE! The linter uses the plural resource kind form and everything is spelled in lowercase.

A resource fully qualified name aka FQN is used in the spinach file to identity a resource name i.e. namespace/resource_name.

For example, the FQN of a pod named fred-1234 in the namespace blee will be blee/fred-1234. This provides for differentiating fred/p1 and blee/p1. For cluster wide resources, the FQN is equivalent to the name. Exclude rules can be either a straight string match or a regular expression. In the latter case the regular expression must be specified via the rx: prefix.

NOTE! Please be careful with your regex as more resources than expected may get excluded from the report with a loose regex rule. When your cluster resources change, this could lead to a sub-optimal scans. Thus we recommend running Popeye wide open once in a while to make sure you will pick up on any new issues that may have arisen in your clusters…

Here is an example spinach file as it stands in this release. There is a fuller eks and aks based spinach file in this repo under spinach. (BTW: for new comers into the project, might be a great way to contribute by adding cluster specific spinach file PRs…)

# spinach.yaml

# A Popeye sample configuration file
  # Checks resources against reported metrics usage.
  # If over/under these thresholds a linter warning will be issued.
  # Your cluster must run a metrics-server for these to take place!
      underPercUtilization: 200 # Checks if cpu is under allocated by more than 200% at current load.
      overPercUtilization: 50   # Checks if cpu is over allocated by more than 50% at current load.
      underPercUtilization: 200 # Checks if mem is under allocated by more than 200% at current load.
      overPercUtilization: 50   # Checks if mem is over allocated by more than 50% usage at current load.

  # Excludes excludes certain resources from Popeye scans
    # [NEW!] Global exclude resources and codes globally of any linters.
      fqns: [rx:^kube-] # => excludes all resources in kube-system, kube-public, etc..
      # [NEW!] Exclude resources for all linters matching these labels
        app: [bozo, bono] #=> exclude any resources with labels matching either app=bozo or app=bono
      # [NEW!] Exclude resources for all linters matching these annotations
        fred: [blee, duh] # => exclude any resources with annotations matching either fred=blee or fred=duh
      # [NEW!] Exclude scan codes globally via straight codes or regex!
      codes: ["300", "206", "rx:^41"] # => exclude issue codes 300, 206, 410, 415 (Note: regex match!)

    # [NEW!] Configure individual resource linters
      # Configure the namespaces linter for v1/namespaces
        # [NEW!] Exclude these codes for all namespace resources straight up or via regex.
        codes: ["100", "rx:^22"] # => exclude codes 100, 220, 225, ...
        # [NEW!] Excludes specific namespaces from the scan
          - fqns: [kube-public, kube-system] # => skip ns kube-pulbic and kube-system
          - fqns: [blee-ns]
            codes: [106] # => skip code 106 for namespace blee-ns

      # Skip secrets in namespace bozo.
          - fqns: [rx:^bozo]

      # Configure the pods linter for v1/pods.
          # [NEW!] exclude all pods matching these labels.
          - labels:
              app: [fred,blee] # Exclude codes 102, 105 for any pods with labels app=fred or app=blee
            codes: [102, 105]

    # Configure node resources.
      # Limits set a cpu/mem threshold in % ie if cpu|mem > limit a lint warning is triggered.
        # CPU checks if current CPU utilization on a node is greater than 90%.
        cpu:    90
        # Memory checks if current Memory utilization on a node is greater than 80%.
        memory: 80

    # Configure pod resources
      # Restarts check the restarts count and triggers a lint warning if above threshold.
      restarts: 3
      # Check container resource utilization in percent.
      # Issues a lint warning if about these threshold.
        cpu:    80
        memory: 75

  # [New!] overrides code severity
    # Code specifies a custom severity level ie critical=3, warn=2, info=1
    - code: 206
      severity: 1

  # Configure a list of allowed registries to pull images from.
  # Any resources not using the following registries will be flagged!
    - quay.io
    - docker.io

In Cluster

Popeye is containerized and can be run directly in your Kubernetes clusters as a one-off or CronJob.

Here is a sample setup, please modify per your needs/wants. The manifests for this are in the k8s directory in this repo.

kubectl apply -f k8s/popeye
apiVersion: v1
kind: Namespace
  name:      popeye
apiVersion: batch/v1
kind: CronJob
  name:      popeye
  namespace: popeye
  schedule: "* */1 * * *" # Fire off Popeye once an hour
  concurrencyPolicy: Forbid
          serviceAccountName: popeye
          restartPolicy: Never
            - name: popeye
              image: derailed/popeye:vX.Y.Z
              imagePullPolicy: IfNotPresent
                - -o
                - yaml
                - --force-exit-zero
                  cpu:    500m
                  memory: 100Mi

The --force-exit-zero should be set. Otherwise, the pods will end up in an error state.

NOTE! Popeye exits with a non-zero error code if any lint errors are detected.

Popeye Got Your RBAC!

In order for Popeye to do his work, the signed-in user must have enough RBAC oomph to get/list the resources mentioned above.

Sample Popeye RBAC Rules (please note that those are subject to change.)

NOTE! Please review and tune per your cluster policies.

# Popeye ServiceAccount.
apiVersion: v1
kind:       ServiceAccount
  name:      popeye
  namespace: popeye

# Popeye needs get/list access on the following Kubernetes resources.
apiVersion: rbac.authorization.k8s.io/v1
kind:       ClusterRole
  name: popeye
- apiGroups: [""]
   - configmaps
   - endpoints
   - namespaces
   - nodes
   - persistentvolumes
   - persistentvolumeclaims
   - pods
   - secrets
   - serviceaccounts
   - services
  verbs:     ["get", "list"]
- apiGroups: ["apps"]
  - daemonsets
  - deployments
  - statefulsets
  - replicasets
  verbs:     ["get", "list"]
- apiGroups: ["networking.k8s.io"]
  - ingresses
  - networkpolicies
  verbs:     ["get", "list"]
- apiGroups: ["batch.k8s.io"]
  - cronjobs
  - jobs
  verbs:     ["get", "list"]
- apiGroups: ["gateway.networking.k8s.io"]
  - gateway-classes
  - gateways
  - httproutes
  verbs:     ["get", "list"]
- apiGroups: ["autoscaling"]
  - horizontalpodautoscalers
  verbs:     ["get", "list"]
- apiGroups: ["policy"]
  - poddisruptionbudgets
  - podsecuritypolicies
  verbs:     ["get", "list"]
- apiGroups: ["rbac.authorization.k8s.io"]
  - clusterroles
  - clusterrolebindings
  - roles
  - rolebindings
  verbs:     ["get", "list"]
- apiGroups: ["metrics.k8s.io"]
  - pods
  - nodes
  verbs:     ["get", "list"]

# Binds Popeye to this ClusterRole.
apiVersion: rbac.authorization.k8s.io/v1
kind:       ClusterRoleBinding
  name: popeye
- kind:     ServiceAccount
  name:     popeye
  namespace: popeye
  kind:     ClusterRole
  name:     popeye
  apiGroup: rbac.authorization.k8s.io

Report Morphology

The lint report outputs each resource group scanned and their potential issues. The report is color/emoji coded in term of linter severity levels:

Level Icon Jurassic Color Description
Ok OK Green Happy!
Info 🔊 I BlueGreen FYI
Warn 😱 W Yellow Potential Issue
Error 💥 E Red Action required

The heading section for each scanned Kubernetes resource provides a summary count for each of the categories above.

The Summary section provides a Popeye Score based on the linter pass on the given cluster.

Known Issues

This initial drop is brittle. Popeye will most likely blow up when…


This is work in progress! If there is enough interest in the Kubernetes community, we will enhance per your recommendations/contributions. Also if you dig this effort, please let us know that too!

ATTA Girls/Boys!

Popeye sits on top of many of open source projects and libraries. Our sincere appreciations to all the OSS contributors that work nights and weekends to make this project a reality!

Contact Info

  1. Email: fernand@imhotep.io
  2. Twitter: @kitesurfer

 © 2024 Imhotep Software LLC. All materials licensed under Apache v2.0