Troubleshooting

This section provides resolution steps for common problems reported with the linkerd check command.

The “pre-kubernetes-cluster-setup” checks

These checks only run when the --pre flag is set. This flag is intended for use prior to running linkerd install, to verify your cluster is prepared for installation.

√ control plane namespace does not already exist

Example failure:

  1. × control plane namespace does not already exist
  2.     The "linkerd" namespace already exists

By default linkerd install will create a linkerd namespace. Prior to installation, that namespace should not exist. To check with a different namespace, run:

  1. linkerd check --pre --linkerd-namespace linkerd-test

√ can create Kubernetes resources

The subsequent checks in this section validate whether you have permission to create the Kubernetes resources required for Linkerd installation, specifically:

  1. √ can create Namespaces
  2. √ can create ClusterRoles
  3. √ can create ClusterRoleBindings
  4. √ can create CustomResourceDefinitions

The “pre-kubernetes-setup” checks

These checks only run when the --pre flag is set This flag is intended for use prior to running linkerd install, to verify you have the correct RBAC permissions to install Linkerd.

  1. √ can create Namespaces
  2. √ can create ClusterRoles
  3. √ can create ClusterRoleBindings
  4. √ can create CustomResourceDefinitions
  5. √ can create PodSecurityPolicies
  6. √ can create ServiceAccounts
  7. √ can create Services
  8. √ can create Deployments
  9. √ can create ConfigMaps

√ no clock skew detected

This check detects any differences between the system running the linkerd install command and the Kubernetes nodes (known as clock skew). Having a substantial clock skew can cause TLS validation problems because a node may determine that a TLS certificate is expired when it should not be, or vice versa.

Linkerd version edge-20.3.4 and later check for a difference of at most 5 minutes and older versions of Linkerd (including stable-2.7) check for a difference of at most 1 minute. If your Kubernetes node heartbeat interval is longer than this difference, you may experience false positives of this check. The default node heartbeat interval was increased to 5 minutes in Kubernetes 1.17 meaning that users running Linkerd versions prior to edge-20.3.4 on Kubernetes 1.17 or later are likely to experience these false positives. If this is the case, you can upgrade to Linkerd edge-20.3.4 or later. If you choose to ignore this error, we strongly recommend that you verify that your system clocks are consistent.

The “pre-kubernetes-capability” checks

These checks only run when the --pre flag is set. This flag is intended for use prior to running linkerd install, to verify you have the correct Kubernetes capability permissions to install Linkerd.

√ has NET_ADMIN capability

Example failure:

  1. × has NET_ADMIN capability
  2.     found 3 PodSecurityPolicies, but none provide NET_ADMIN
  3.     see https://linkerd.io/checks/#pre-k8s-cluster-net-admin for hints

Linkerd installation requires the NET_ADMIN Kubernetes capability, to allow for modification of iptables.

For more information, see the Kubernetes documentation on Pod Security Policies, Security Contexts, and the man page on Linux Capabilities.

√ has NET_RAW capability

Example failure:

  1. × has NET_RAW capability
  2.     found 3 PodSecurityPolicies, but none provide NET_RAW
  3.     see https://linkerd.io/checks/#pre-k8s-cluster-net-raw for hints

Linkerd installation requires the NET_RAW Kubernetes capability, to allow for modification of iptables.

For more information, see the Kubernetes documentation on Pod Security Policies, Security Contexts, and the man page on Linux Capabilities.

The “pre-linkerd-global-resources” checks

These checks only run when the --pre flag is set. This flag is intended for use prior to running linkerd install, to verify you have not already installed the Linkerd control plane.

  1. √ no ClusterRoles exist
  2. √ no ClusterRoleBindings exist
  3. √ no CustomResourceDefinitions exist
  4. √ no MutatingWebhookConfigurations exist
  5. √ no ValidatingWebhookConfigurations exist
  6. √ no PodSecurityPolicies exist

The “pre-kubernetes-single-namespace-setup” checks

If you do not expect to have the permission for a full cluster install, try the --single-namespace flag, which validates if Linkerd can be installed in a single namespace, with limited cluster access:

  1. linkerd check --pre --single-namespace

√ control plane namespace exists

  1. × control plane namespace exists
  2.     The "linkerd" namespace does not exist

In --single-namespace mode, linkerd check assumes that the installer does not have permission to create a namespace, so the installation namespace must already exist.

By default the linkerd namespace is used. To use a different namespace run:

  1. linkerd check --pre --single-namespace --linkerd-namespace linkerd-test

√ can create Kubernetes resources

The subsequent checks in this section validate whether you have permission to create the Kubernetes resources required for Linkerd --single-namespace installation, specifically:

  1. √ can create Roles
  2. √ can create RoleBindings

For more information on cluster access, see the GKE Setup section above.

The “kubernetes-api” checks

Example failures:

  1. × can initialize the client
  2.     error configuring Kubernetes API client: stat badconfig: no such file or directory
  3. × can query the Kubernetes API
  4.     Get https://8.8.8.8/version: dial tcp 8.8.8.8:443: i/o timeout

Ensure that your system is configured to connect to a Kubernetes cluster. Validate that the KUBECONFIG environment variable is set properly, and/or ~/.kube/config points to a valid cluster.

For more information see these pages in the Kubernetes Documentation:

Also verify that these command works:

  1. kubectl config view
  2. kubectl cluster-info
  3. kubectl version

Another example failure:

  1. ✘ can query the Kubernetes API
  2.     Get REDACTED/version: x509: certificate signed by unknown authority

As an (unsafe) workaround to this, you may try:

  1. kubectl config set-cluster ${KUBE_CONTEXT} --insecure-skip-tls-verify=true \
  2.     --server=${KUBE_CONTEXT}

The “kubernetes-version” checks

√ is running the minimum Kubernetes API version

Example failure:

  1. × is running the minimum Kubernetes API version
  2.     Kubernetes is on version [1.7.16], but version [1.13.0] or more recent is required

Linkerd requires at least version 1.13.0. Verify your cluster version with:

  1. kubectl version

√ is running the minimum kubectl version

Example failure:

  1. × is running the minimum kubectl version
  2.     kubectl is on version [1.9.1], but version [1.13.0] or more recent is required
  3.     see https://linkerd.io/checks/#kubectl-version for hints

Linkerd requires at least version 1.13.0. Verify your kubectl version with:

  1. kubectl version --client --short

To fix please update kubectl version.

For more information on upgrading Kubernetes, see the page in the Kubernetes Documentation on Upgrading a cluster

The “linkerd-config” checks

This category of checks validates that Linkerd’s cluster-wide RBAC and related resources have been installed. These checks run via a default linkerd check, and also in the context of a multi-stage setup, for example:

  1. # install cluster-wide resources (first stage)
  2. linkerd install config | kubectl apply -f -
  4. # validate successful cluster-wide resources installation
  5. linkerd check config
  7. # install Linkerd control plane
  8. linkerd install control-plane | kubectl apply -f -
  10. # validate successful control-plane installation
  11. linkerd check

√ control plane Namespace exists

Example failure:

  1. × control plane Namespace exists
  2.     The "foo" namespace does not exist
  3.     see https://linkerd.io/checks/#l5d-existence-ns for hints

Ensure the Linkerd control plane namespace exists:

  1. kubectl get ns

The default control plane namespace is linkerd. If you installed Linkerd into a different namespace, specify that in your check command:

  1. linkerd check --linkerd-namespace linkerdtest

√ control plane ClusterRoles exist

Example failure:

  1. × control plane ClusterRoles exist
  2.     missing ClusterRoles: linkerd-linkerd-controller
  3.     see https://linkerd.io/checks/#l5d-existence-cr for hints

Ensure the Linkerd ClusterRoles exist:

  1. $ kubectl get clusterroles | grep linkerd
  2. linkerd-linkerd-controller                                             9d
  3. linkerd-linkerd-identity                                               9d
  4. linkerd-linkerd-prometheus                                             9d
  5. linkerd-linkerd-proxy-injector                                         20d
  6. linkerd-linkerd-sp-validator                                           9d

Also ensure you have permission to create ClusterRoles:

  1. $ kubectl auth can-i create clusterroles
  2. yes

√ control plane ClusterRoleBindings exist

Example failure:

  1. × control plane ClusterRoleBindings exist
  2.     missing ClusterRoleBindings: linkerd-linkerd-controller
  3.     see https://linkerd.io/checks/#l5d-existence-crb for hints

Ensure the Linkerd ClusterRoleBindings exist:

  1. $ kubectl get clusterrolebindings | grep linkerd
  2. linkerd-linkerd-controller                             9d
  3. linkerd-linkerd-identity                               9d
  4. linkerd-linkerd-prometheus                             9d
  5. linkerd-linkerd-proxy-injector                         20d
  6. linkerd-linkerd-sp-validator                           9d

Also ensure you have permission to create ClusterRoleBindings:

  1. $ kubectl auth can-i create clusterrolebindings
  2. yes

√ control plane ServiceAccounts exist

Example failure:

  1. × control plane ServiceAccounts exist
  2.     missing ServiceAccounts: linkerd-controller
  3.     see https://linkerd.io/checks/#l5d-existence-sa for hints

Ensure the Linkerd ServiceAccounts exist:

  1. $ kubectl -n linkerd get serviceaccounts
  2. NAME                     SECRETS   AGE
  3. default                  1         23m
  4. linkerd-controller       1         23m
  5. linkerd-grafana          1         23m
  6. linkerd-identity         1         23m
  7. linkerd-prometheus       1         23m
  8. linkerd-proxy-injector   1         7m
  9. linkerd-sp-validator     1         23m
  10. linkerd-web              1         23m

Also ensure you have permission to create ServiceAccounts in the Linkerd namespace:

  1. $ kubectl -n linkerd auth can-i create serviceaccounts
  2. yes

√ control plane CustomResourceDefinitions exist

Example failure:

  1. × control plane CustomResourceDefinitions exist
  2.     missing CustomResourceDefinitions: serviceprofiles.linkerd.io
  3.     see https://linkerd.io/checks/#l5d-existence-crd for hints

Ensure the Linkerd CRD exists:

  1. $ kubectl get customresourcedefinitions
  2. NAME                         CREATED AT
  3. serviceprofiles.linkerd.io   2019-04-25T21:47:31Z

Also ensure you have permission to create CRDs:

  1. $ kubectl auth can-i create customresourcedefinitions
  2. yes

√ control plane MutatingWebhookConfigurations exist

Example failure:

  1. × control plane MutatingWebhookConfigurations exist
  2.     missing MutatingWebhookConfigurations: linkerd-proxy-injector-webhook-config
  3.     see https://linkerd.io/checks/#l5d-existence-mwc for hints

Ensure the Linkerd MutatingWebhookConfigurations exists:

  1. $ kubectl get mutatingwebhookconfigurations | grep linkerd
  2. linkerd-proxy-injector-webhook-config   2019-07-01T13:13:26Z

Also ensure you have permission to create MutatingWebhookConfigurations:

  1. $ kubectl auth can-i create mutatingwebhookconfigurations
  2. yes

√ control plane ValidatingWebhookConfigurations exist

Example failure:

  1. × control plane ValidatingWebhookConfigurations exist
  2.     missing ValidatingWebhookConfigurations: linkerd-sp-validator-webhook-config
  3.     see https://linkerd.io/checks/#l5d-existence-vwc for hints

Ensure the Linkerd ValidatingWebhookConfiguration exists:

  1. $ kubectl get validatingwebhookconfigurations | grep linkerd
  2. linkerd-sp-validator-webhook-config   2019-07-01T13:13:26Z

Also ensure you have permission to create ValidatingWebhookConfigurations:

  1. $ kubectl auth can-i create validatingwebhookconfigurations
  2. yes

√ control plane PodSecurityPolicies exist

Example failure:

  1. × control plane PodSecurityPolicies exist
  2.     missing PodSecurityPolicies: linkerd-linkerd-control-plane
  3.     see https://linkerd.io/checks/#l5d-existence-psp for hints

Ensure the Linkerd PodSecurityPolicy exists:

  1. $ kubectl get podsecuritypolicies | grep linkerd
  2. linkerd-linkerd-control-plane   false   NET_ADMIN,NET_RAW   RunAsAny   RunAsAny    MustRunAs   MustRunAs   true             configMap,emptyDir,secret,projected,downwardAPI,persistentVolumeClaim

Also ensure you have permission to create PodSecurityPolicies:

  1. $ kubectl auth can-i create podsecuritypolicies
  2. yes

The “linkerd-existence” checks

√ ‘linkerd-config’ config map exists

Example failure:

  1. × 'linkerd-config' config map exists
  2.     missing ConfigMaps: linkerd-config
  3.     see https://linkerd.io/checks/#l5d-existence-linkerd-config for hints

Ensure the Linkerd ConfigMap exists:

  1. $ kubectl -n linkerd get configmap/linkerd-config
  2. NAME             DATA   AGE
  3. linkerd-config   3      61m

Also ensure you have permission to create ConfigMaps:

  1. $ kubectl -n linkerd auth can-i create configmap
  2. yes

√ control plane replica sets are ready

This failure occurs when one of Linkerd’s ReplicaSets fails to schedule a pod.

For more information, see the Kubernetes documentation on Failed Deployments.

√ no unschedulable pods

Example failure:

  1. × no unschedulable pods
  2.     linkerd-prometheus-6b668f774d-j8ncr: 0/1 nodes are available: 1 Insufficient cpu.
  3.     see https://linkerd.io/checks/#l5d-existence-unschedulable-pods for hints

For more information, see the Kubernetes documentation on the Unschedulable Pod Condition.

√ controller pod is running

Example failure:

  1. × controller pod is running
  2.     No running pods for "linkerd-controller"

Note, it takes a little bit for pods to be scheduled, images to be pulled and everything to start up. If this is a permanent error, you’ll want to validate the state of the controller pod with:

  1. $ kubectl -n linkerd get po --selector linkerd.io/control-plane-component=controller
  2. NAME                                  READY     STATUS    RESTARTS   AGE
  3. linkerd-controller-7bb8ff5967-zg265   4/4       Running   0          40m

Check the controller’s logs with:

  1. linkerd logs --control-plane-component controller

√ can initialize the client

Example failure:

  1. × can initialize the client
  2.     parse http:// bad/: invalid character " " in host name

Verify that a well-formed --api-addr parameter was specified, if any:

  1. linkerd check --api-addr " bad"

√ can query the control plane API

Example failure:

  1. × can query the control plane API
  2.     Post http://8.8.8.8/api/v1/Version: context deadline exceeded

This check indicates a connectivity failure between the cli and the Linkerd control plane. To verify connectivity, manually connect to the controller pod:

  1. kubectl -n linkerd port-forward \
  2.     $(kubectl -n linkerd get po \
  3.         --selector=linkerd.io/control-plane-component=controller \
  4.         -o jsonpath='{.items[*].metadata.name}') \
  5. 9995:9995

…and then curl the /metrics endpoint:

  1. curl localhost:9995/metrics

The “linkerd-identity” checks

√ certificate config is valid

Example failures:

  1. × certificate config is valid
  2.     key ca.crt containing the trust anchors needs to exist in secret linkerd-identity-issuer if --identity-external-issuer=true
  3.     see https://linkerd.io/checks/#l5d-identity-cert-config-valid
  1. × certificate config is valid
  2.     key crt.pem containing the issuer certificate needs to exist in secret linkerd-identity-issuer if --identity-external-issuer=false
  3.     see https://linkerd.io/checks/#l5d-identity-cert-config-valid

Ensure that your linkerd-identity-issuer secret contains the correct keys for the scheme that Linkerd is configured with. If the scheme is kubernetes.io/tls your secret should contain the tls.crt, tls.key and ca.crt keys. Alternatively if your scheme is linkerd.io/tls, the required keys are crt.pem and key.pem.

√ trust roots are using supported crypto algorithm

Example failure:

  1. × trust roots are using supported crypto algorithm
  2.     Invalid roots:
  3.         * 165223702412626077778653586125774349756 identity.linkerd.cluster.local must use P-256 curve for public key, instead P-521 was used
  4.     see https://linkerd.io/checks/#l5d-identity-trustAnchors-use-supported-crypto

You need to ensure that all of your roots use ECDSA P-256 for their public key algorithm.

√ trust roots are within their validity period

Example failure:

  1. × trust roots are within their validity period
  2.     Invalid roots:
  3.         * 199607941798581518463476688845828639279 identity.linkerd.cluster.local not valid anymore. Expired on 2019-12-19T13:08:18Z
  4.     see https://linkerd.io/checks/#l5d-identity-trustAnchors-are-time-valid for hints

Failures of such nature indicate that your roots have expired. If that is the case you will have to update both the root and issuer certificates at once. You can follow the process outlined in Replacing Expired Certificates to get your cluster back to a stable state.

√ trust roots are valid for at least 60 days

Example warnings:

  1. ‼ trust roots are valid for at least 60 days
  2.     Roots expiring soon:
  3.         * 66509928892441932260491975092256847205 identity.linkerd.cluster.local will expire on 2019-12-19T13:30:57Z
  4.     see https://linkerd.io/checks/#l5d-identity-trustAnchors-not-expiring-soon for hints

This warning indicates that the expiry of some of your roots is approaching. In order to address this problem without incurring downtime, you can follow the process outlined in Rotating your identity certificates.

√ issuer cert is using supported crypto algorithm

Example failure:

  1. × issuer cert is using supported crypto algorithm
  2.     issuer certificate must use P-256 curve for public key, instead P-521 was used
  3.     see https://linkerd.io/checks/#5d-identity-issuer-cert-uses-supported-crypto for hints

You need to ensure that your issuer certificate uses ECDSA P-256 for its public key algorithm. You can refer to Generating your own mTLS root certificates to see how you can generate certificates that will work with Linkerd.

√ issuer cert is within its validity period

Example failure:

  1. × issuer cert is within its validity period
  2.     issuer certificate is not valid anymore. Expired on 2019-12-19T13:35:49Z
  3.     see https://linkerd.io/checks/#l5d-identity-issuer-cert-is-time-valid

This failure indicates that your issuer certificate has expired. In order to bring your cluster back to a valid state, follow the process outlined in Replacing Expired Certificates.

√ issuer cert is valid for at least 60 days

Example warning:

  1. ‼ issuer cert is valid for at least 60 days
  2.     issuer certificate will expire on 2019-12-19T13:35:49Z
  3.     see https://linkerd.io/checks/#l5d-identity-issuer-cert-not-expiring-soon for hints

This warning means that your issuer certificate is expiring soon. If you do not rely on external certificate management solution such as cert-manager, you can follow the process outlined in Rotating your identity certificates

√ issuer cert is issued by the trust root

Example error:

  1. × issuer cert is issued by the trust root
  2.     x509: certificate signed by unknown authority (possibly because of "x509: ECDSA verification failure" while trying to verify candidate authority certificate "identity.linkerd.cluster.local")
  3.     see https://linkerd.io/checks/#l5d-identity-issuer-cert-issued-by-trust-anchor for hints

This error indicates that the issuer certificate that is in the linkerd-identity-issuer secret cannot be verified with any of the roots that Linkerd has been configured with. Using the CLI install process, this should never happen. If Helm was used for installation or the issuer certificates are managed by a malfunctioning certificate management solution, it is possible for the cluster to end up in such an invalid state. At that point the best to do is to use the upgrade command to update your certificates:

  1. linkerd upgrade \
  2.     --identity-issuer-certificate-file=./your-new-issuer.crt \
  3.     --identity-issuer-key-file=./your-new-issuer.key \
  4.     --identity-trust-anchors-file=./your-new-roots.crt \
  5.     --force | kubectl apply -f -

Once the upgrade process is over, the output of linkerd check --proxy should be:

  1. linkerd-identity
  2. ----------------
  3. √ certificate config is valid
  4. √ trust roots are using supported crypto algorithm
  5. √ trust roots are within their validity period
  6. √ trust roots are valid for at least 60 days
  7. √ issuer cert is using supported crypto algorithm
  8. √ issuer cert is within its validity period
  9. √ issuer cert is valid for at least 60 days
  10. √ issuer cert is issued by the trust root
  12. linkerd-identity-data-plane
  13. ---------------------------
  14. √ data plane proxies certificate match CA

The “linkerd-webhooks-and-apisvc-tls” checks

√ tap API server has valid cert

Example failure:

  1. × tap API server has valid cert
  2.     secrets "linkerd-tap-tls" not found
  3.     see https://linkerd.io/checks/#l5d-tap-cert-valid for hints

Ensure that the linkerd-tap-k8s-tls secret exists and contains the appropriate tls.crt and tls.key data entries. For versions before 2.9, the secret is named linkerd-tap-tls and it should contain the crt.pem and key.pem data entries.

  1. × tap API server has valid cert
  2.     cert is not issued by the trust anchor: x509: certificate is valid for xxxxxx, not linkerd-tap.linkerd.svc
  3.     see https://linkerd.io/checks/#l5d-tap-cert-valid for hints

Here you need to make sure the certificate was issued specifically for linkerd-tap.linkerd.svc.

√ webhook cert is valid for at least 60 days

Example failure:

  1. ‼ tap API server cert is valid for at least 60 days
  2.     certificate will expire on 2020-11-07T17:00:07Z
  3.     see https://linkerd.io/checks/#l5d-webhook-cert-not-expiring-soon for hints

This warning indicates that the expiry of one of your webhooks (tap API server, proxy-injector or sp-validator) cert is approaching. In order to address this problem without incurring downtime, you can follow the process outlined in Automatically Rotating your webhook TLS Credentials.

√ proxy-injector webhook has valid cert

Example failure:

  1. × proxy-injector webhook has valid cert
  2.     secrets "linkerd-proxy-injector-tls" not found
  3.     see https://linkerd.io/checks/#l5d-proxy-injector-webhook-cert-valid for hints

Ensure that the linkerd-proxy-injector-k8s-tls secret exists and contains the appropriate tls.crt and tls.key data entries. For versions before 2.9, the secret is named linkerd-proxy-injector-tls and it should contain the crt.pem and key.pem data entries.

  1. × proxy-injector webhook has valid cert
  2.     cert is not issued by the trust anchor: x509: certificate is valid for xxxxxx, not linkerd-proxy-injector.linkerd.svc
  3.     see https://linkerd.io/checks/#l5d-proxy-injector-webhook-cert-valid for hints

Here you need to make sure the certificate was issued specifically for linkerd-proxy-injector.linkerd.svc.

√ sp-validator webhook has valid cert

Example failure:

  1. × sp-validator webhook has valid cert
  2.     secrets "linkerd-sp-validator-tls" not found
  3.     see https://linkerd.io/checks/#l5d-sp-validator-webhook-cert-valid for hints

Ensure that the linkerd-sp-validator-k8s-tls secret exists and contains the appropriate tls.crt and tls.key data entries. For versions before 2.9, the secret is named linkerd-sp-validator-tls and it should contain the crt.pem and key.pem data entries.

  1. × sp-validator webhook has valid cert
  2.     cert is not issued by the trust anchor: x509: certificate is valid for xxxxxx, not linkerd-sp-validator.linkerd.svc
  3.     see https://linkerd.io/checks/#l5d-sp-validator-webhook-cert-valid for hints

Here you need to make sure the certificate was issued specifically for linkerd-sp-validator.linkerd.svc.

The “linkerd-identity-data-plane” checks

√ data plane proxies certificate match CA

Example warning:

  1. ‼ data plane proxies certificate match CA
  2.     Some pods do not have the current trust bundle and must be restarted:
  3.         * emojivoto/emoji-d8d7d9c6b-8qwfx
  4.         * emojivoto/vote-bot-588499c9f6-zpwz6
  5.         * emojivoto/voting-8599548fdc-6v64k
  6.     see https://linkerd.io/checks/{#l5d-identity-data-plane-proxies-certs-match-ca for hints

Observing this warning indicates that some of your meshed pods have proxies that have stale certificates. This is most likely to happen during upgrade operations that deal with cert rotation. In order to solve the problem you can use rollout restart to restart the pods in question. That should cause them to pick the correct certs from the linkerd-config configmap. When upgrade is performed using the --identity-trust-anchors-file flag to modify the roots, the Linkerd components are restarted. While this operation is in progress the check --proxy command may output a warning, pertaining to the Linkerd components:

  1. ‼ data plane proxies certificate match CA
  2.     Some pods do not have the current trust bundle and must be restarted:
  3.         * linkerd/linkerd-sp-validator-75f9d96dc-rch4x
  4.         * linkerd/linkerd-tap-68d8bbf64-mpzgb
  5.         * linkerd/linkerd-web-849f74b7c6-qlhwc
  6.     see https://linkerd.io/checks/{#l5d-identity-data-plane-proxies-certs-match-ca for hints

If that is the case, simply wait for the upgrade operation to complete. The stale pods should terminate and be replaced by new ones, configured with the correct certificates.

The “linkerd-api” checks

√ control plane pods are ready

Example failure:

  1. × control plane pods are ready
  2.     No running pods for "linkerd-web"

Verify the state of the control plane pods with:

  1. $ kubectl -n linkerd get po
  2. NAME                                      READY     STATUS    RESTARTS   AGE
  3. pod/linkerd-controller-b8c4c48c8-pflc9    4/4       Running   0          45m
  4. pod/linkerd-grafana-776cf777b6-lg2dd      2/2       Running   0          1h
  5. pod/linkerd-prometheus-74d66f86f6-6t6dh   2/2       Running   0          1h
  6. pod/linkerd-web-5f6c45d6d9-9hd9j          2/2       Running   0          3m

√ control plane self-check

Example failure:

  1. × control plane self-check
  2.     Post https://localhost:6443/api/v1/namespaces/linkerd/services/linkerd-controller-api:http/proxy/api/v1/SelfCheck: context deadline exceeded

Check the logs on the control-plane’s public API:

  1. linkerd logs --control-plane-component controller --container public-api

√ [kubernetes] control plane can talk to Kubernetes

Example failure:

  1. × [kubernetes] control plane can talk to Kubernetes
  2.     Error calling the Kubernetes API: FAIL

Check the logs on the control-plane’s public API:

  1. linkerd logs --control-plane-component controller --container public-api

√ [prometheus] control plane can talk to Prometheus

Example failure:

  1. × [prometheus] control plane can talk to Prometheus
  2.     Error calling Prometheus from the control plane: FAIL

Note

This will fail if you have changed your default cluster domain from cluster.local, see the associated issue for more information and potential workarounds.

Validate that the Prometheus instance is up and running:

  1. kubectl -n linkerd get all | grep prometheus

Check the Prometheus logs:

  1. linkerd logs --control-plane-component prometheus

Check the logs on the control-plane’s public API:

  1. linkerd logs --control-plane-component controller --container public-api

√ tap api service is running

Example failure:

  1. × FailedDiscoveryCheck: no response from https://10.233.31.133:443: Get https://10.233.31.133:443: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)

tap uses the kubernetes Aggregated Api-Server model to allow users to have k8s RBAC on top. This model has the following specific requirements in the cluster:

The “linkerd-service-profile” checks

Example failure:

  1. ‼ no invalid service profiles
  2.     ServiceProfile "bad" has invalid name (must be "<service>.<namespace>.svc.cluster.local")

Validate the structure of your service profiles:

  1. $ kubectl -n linkerd get sp
  2. NAME                                               AGE
  3. bad                                                51s
  4. linkerd-controller-api.linkerd.svc.cluster.local   1m

Example failure:

  1. ‼ no invalid service profiles
  2.     the server could not find the requested resource (get serviceprofiles.linkerd.io)

Validate that the Service Profile CRD is installed on your cluster and that its linkerd.io/created-by annotation matches your linkerd version client version:

  1. kubectl get crd/serviceprofiles.linkerd.io -o yaml | grep linkerd.io/created-by

If the CRD is missing or out-of-date you can update it:

  1. linkerd upgrade | kubectl apply -f -

The “linkerd-version” checks

√ can determine the latest version

Example failure:

  1. × can determine the latest version
  2.     Get https://versioncheck.linkerd.io/version.json?version=edge-19.1.2&uuid=test-uuid&source=cli: context deadline exceeded

Ensure you can connect to the Linkerd version check endpoint from the environment the linkerd cli is running:

  1. $ curl "https://versioncheck.linkerd.io/version.json?version=edge-19.1.2&uuid=test-uuid&source=cli"
  2. {"stable":"stable-2.1.0","edge":"edge-19.1.2"}

√ cli is up-to-date

Example failure:

  1. ‼ cli is up-to-date
  2.     is running version 19.1.1 but the latest edge version is 19.1.2

See the page on Upgrading Linkerd.

The “control-plane-version” checks

Example failures:

  1. ‼ control plane is up-to-date
  2.     is running version 19.1.1 but the latest edge version is 19.1.2
  3. ‼ control plane and cli versions match
  4.     mismatched channels: running stable-2.1.0 but retrieved edge-19.1.2

See the page on Upgrading Linkerd.

The “linkerd-data-plane” checks

These checks only run when the --proxy flag is set. This flag is intended for use after running linkerd inject, to verify the injected proxies are operating normally.

√ data plane namespace exists

Example failure:

  1. $ linkerd check --proxy --namespace foo
  2. ...
  3. × data plane namespace exists
  4.     The "foo" namespace does not exist

Ensure the --namespace specified exists, or, omit the parameter to check all namespaces.

√ data plane proxies are ready

Example failure:

  1. × data plane proxies are ready
  2.     No "linkerd-proxy" containers found

Ensure you have injected the Linkerd proxy into your application via the linkerd inject command.

For more information on linkerd inject, see Step 5: Install the demo app in our Getting Started guide.

√ data plane proxy metrics are present in Prometheus

Example failure:

  1. × data plane proxy metrics are present in Prometheus
  2.     Data plane metrics not found for linkerd/linkerd-controller-b8c4c48c8-pflc9.

Ensure Prometheus can connect to each linkerd-proxy via the Prometheus dashboard:

  1. kubectl -n linkerd port-forward svc/linkerd-prometheus 9090

…and then browse to http://localhost:9090/targets, validate the linkerd-proxy section.

You should see all your pods here. If they are not:

  • Prometheus might be experiencing connectivity issues with the k8s api server. Check out the logs and delete the pod to flush any possible transient errors.

√ data plane is up-to-date

Example failure:

  1. ‼ data plane is up-to-date
  2.     linkerd/linkerd-prometheus-74d66f86f6-6t6dh: is running version 19.1.2 but the latest edge version is 19.1.3

See the page on Upgrading Linkerd.

√ data plane and cli versions match

  1. ‼ data plane and cli versions match
  2.     linkerd/linkerd-web-5f6c45d6d9-9hd9j: is running version 19.1.2 but the latest edge version is 19.1.3

See the page on Upgrading Linkerd.

The “linkerd-ha-checks” checks

These checks are ran if Linkerd has been installed in HA mode.

√ pod injection disabled on kube-system

Example warning:

  1. ‼ pod injection disabled on kube-system
  2.     kube-system namespace needs to have the label config.linkerd.io/admission-webhooks: disabled if HA mode is enabled
  3.     see https://linkerd.io/checks/#l5d-injection-disabled for hints

Ensure the kube-system namespace has the config.linkerd.io/admission-webhooks:disabled label:

  1. $ kubectl get namespace kube-system -oyaml
  2. kind: Namespace
  3. apiVersion: v1
  4. metadata:
  5.   name: kube-system
  6.   annotations:
  7.     linkerd.io/inject: disabled
  8.   labels:
  9.     config.linkerd.io/admission-webhooks: disabled

√ multiple replicas of control plane pods

Example warning:

  1. ‼ multiple replicas of control plane pods
  2.     not enough replicas available for [linkerd-controller]
  3.     see https://linkerd.io/checks/#l5d-control-plane-replicas for hints

This happens when one of the control plane pods doesn’t have at least two replicas running. This is likely caused by insufficient node resources.

The “linkerd-cni-plugin” checks

These checks run if Linkerd has been installed with the --linkerd-cni-enabled flag. Alternatively they can be run as part of the pre-checks by providing the --linkerd-cni-enabled flag. Most of these checks verify that the required resources are in place. If any of them are missing, you can use linkerd install-cni | kubectl apply -f - to re-install them.

√ cni plugin ConfigMap exists

Example error:

  1. × cni plugin ConfigMap exists
  2.     configmaps "linkerd-cni-config" not found
  3.     see https://linkerd.io/checks/#cni-plugin-cm-exists for hints

Ensure that the linkerd-cni-config ConfigMap exists in the CNI namespace:

  1. $ kubectl get cm linkerd-cni-config -n linkerd-cni
  2. NAME                      PRIV    CAPS   SELINUX    RUNASUSER   FSGROUP    SUPGROUP   READONLYROOTFS   VOLUMES
  3. linkerd-linkerd-cni-cni   false          RunAsAny   RunAsAny    RunAsAny   RunAsAny   false            hostPath,secret

Also ensure you have permission to create ConfigMaps:

  1. $ kubectl auth can-i create ConfigMaps
  2. yes

√ cni plugin PodSecurityPolicy exists

Example error:

  1. × cni plugin PodSecurityPolicy exists
  2.     missing PodSecurityPolicy: linkerd-linkerd-cni-cni
  3.     see https://linkerd.io/checks/#cni-plugin-psp-exists for hint

Ensure that the pod security policy exists:

  1. $ kubectl get psp linkerd-linkerd-cni-cni
  2. NAME                      PRIV    CAPS   SELINUX    RUNASUSER   FSGROUP    SUPGROUP   READONLYROOTFS   VOLUMES
  3. linkerd-linkerd-cni-cni   false          RunAsAny   RunAsAny    RunAsAny   RunAsAny   false            hostPath,secret

Also ensure you have permission to create PodSecurityPolicies:

  1. $ kubectl auth can-i create PodSecurityPolicies
  2. yes

√ cni plugin ClusterRole exist

Example error:

  1. × cni plugin ClusterRole exists
  2.     missing ClusterRole: linkerd-cni
  3.     see https://linkerd.io/checks/#cni-plugin-cr-exists for hints

Ensure that the cluster role exists:

  1. $ kubectl get clusterrole linkerd-cni
  2. NAME          AGE
  3. linkerd-cni   54m

Also ensure you have permission to create ClusterRoles:

  1. $ kubectl auth can-i create ClusterRoles
  2. yes

√ cni plugin ClusterRoleBinding exist

Example error:

  1. × cni plugin ClusterRoleBinding exists
  2.     missing ClusterRoleBinding: linkerd-cni
  3.     see https://linkerd.io/checks/#cni-plugin-crb-exists for hints

Ensure that the cluster role binding exists:

  1. $ kubectl get clusterrolebinding linkerd-cni
  2. NAME          AGE
  3. linkerd-cni   54m

Also ensure you have permission to create ClusterRoleBindings:

  1. $ kubectl auth can-i create ClusterRoleBindings
  2. yes

√ cni plugin Role exists

Example error:

  1. × cni plugin Role exists
  2.     missing Role: linkerd-cni
  3.     see https://linkerd.io/checks/#cni-plugin-r-exists for hints

Ensure that the role exists in the CNI namespace:

  1. $ kubectl get role linkerd-cni -n linkerd-cni
  2. NAME          AGE
  3. linkerd-cni   52m

Also ensure you have permission to create Roles:

  1. $ kubectl auth can-i create Roles -n linkerd-cni
  2. yes

√ cni plugin RoleBinding exists

Example error:

  1. × cni plugin RoleBinding exists
  2.     missing RoleBinding: linkerd-cni
  3.     see https://linkerd.io/checks/#cni-plugin-rb-exists for hints

Ensure that the role binding exists in the CNI namespace:

  1. $ kubectl get rolebinding linkerd-cni -n linkerd-cni
  2. NAME          AGE
  3. linkerd-cni   49m

Also ensure you have permission to create RoleBindings:

  1. $ kubectl auth can-i create RoleBindings -n linkerd-cni
  2. yes

√ cni plugin ServiceAccount exists

Example error:

  1. × cni plugin ServiceAccount exists
  2.     missing ServiceAccount: linkerd-cni
  3.     see https://linkerd.io/checks/#cni-plugin-sa-exists for hints

Ensure that the CNI service account exists in the CNI namespace:

  1. $ kubectl get ServiceAccount linkerd-cni -n linkerd-cni
  2. NAME          SECRETS   AGE
  3. linkerd-cni   1         45m

Also ensure you have permission to create ServiceAccount:

  1. $ kubectl auth can-i create ServiceAccounts -n linkerd-cni
  2. yes

√ cni plugin DaemonSet exists

Example error:

  1. × cni plugin DaemonSet exists
  2.     missing DaemonSet: linkerd-cni
  3.     see https://linkerd.io/checks/#cni-plugin-ds-exists for hints

Ensure that the CNI daemonset exists in the CNI namespace:

  1. $ kubectl get ds -n linkerd-cni
  2. NAME          DESIRED   CURRENT   READY   UP-TO-DATE   AVAILABLE   NODE SELECTOR                 AGE
  3. linkerd-cni   1         1         1       1            1           beta.kubernetes.io/os=linux   14m

Also ensure you have permission to create DaemonSets:

  1. $ kubectl auth can-i create DaemonSets -n linkerd-cni
  2. yes

√ cni plugin pod is running on all nodes

Example failure:

  1. ‼ cni plugin pod is running on all nodes
  2.     number ready: 2, number scheduled: 3
  3.     see https://linkerd.io/checks/#cni-plugin-ready

Ensure that all the CNI pods are running:

  1. $ kubectl get po -n linkerd-cn
  2. NAME                READY   STATUS    RESTARTS   AGE
  3. linkerd-cni-rzp2q   1/1     Running   0          9m20s
  4. linkerd-cni-mf564   1/1     Running   0          9m22s
  5. linkerd-cni-p5670   1/1     Running   0          9m25s

Ensure that all pods have finished the deployment of the CNI config and binary:

  1. $ kubectl logs linkerd-cni-rzp2q -n linkerd-cni
  2. Wrote linkerd CNI binaries to /host/opt/cni/bin
  3. Created CNI config /host/etc/cni/net.d/10-kindnet.conflist
  4. Done configuring CNI. Sleep=true

The “linkerd-multicluster checks

These checks run if the service mirroring controller has been installed. Additionally they can be ran if --multicluster flag is specified explicitly. Most of these checks verify that the service mirroring controller is working correctly. Furthermore the checks ensure that end to end TLS is possible between paired clusters.

√ service mirror controller is running

Example error:

  1. × service mirror controller is running
  2.     Service mirror controller is not present
  3.     see https://linkerd.io/checks/#l5d-multicluster-service-mirror-running for hints

Note, it takes a little bit for pods to be scheduled, images to be pulled and everything to start up. If this is a permanent error, you’ll want to validate the state of the controller pod with:

  1. $ kubectl --all-namespaces get po --selector linkerd.io/control-plane-component=linkerd-service-mirror
  2. NAME                                  READY     STATUS    RESTARTS   AGE
  3. linkerd-service-mirror-7bb8ff5967-zg265   2/2       Running   0          50m

√ service mirror controller ClusterRoles exists

Example error:

  1. × service mirror controller ClusterRoles exists
  2.     missing ClusterRoles: linkerd-service-mirror-access-local-resources
  3.     see https://linkerd.io/checks/#l5d-multicluster-cluster-role-exists for hints

Ensure that the cluster role exists:

  1. $ kubectl get clusterrole linkerd-service-mirror-access-local-resources
  2. NAME                                            AGE
  3. linkerd-service-mirror-access-local-resources   54m

Also ensure you have permission to create ClusterRoles:

  1. $ kubectl auth can-i create ClusterRoles
  2. yes

√ service mirror controller ClusterRoleBindings exist

Example error:

  1. × service mirror controller ClusterRoleBindings exist
  2.     missing ClusterRoleBindings: linkerd-service-mirror-access-local-resources
  3.     see https://linkerd.io/checks/#l5d-multicluster-cluster-role-binding-exist for hints

Ensure that the cluster role bindings exists:

  1. $ kubectl get clusterrolebindings linkerd-service-mirror-access-local-resources
  2. NAME                                            AGE
  3. linkerd-service-mirror-access-local-resources   54m

Also ensure you have permission to create ClusterRoleBindings:

  1. $ kubectl auth can-i create ClusterRoleBindings
  2. yes

√ service mirror controller Roles exist

Example error:

  1. × service mirror controller Roles exist
  2.     missing Roles: linkerd-service-mirror-read-remote-creds
  3.     see https://linkerd.io/checks/#l5d-multicluster-role-exist for hints

Ensure that the role exists in the service mirror controller namespace:

  1. $ kubectl get role linkerd-service-mirror-read-remote-creds -n linkerd-multicluster
  2. NAME                                       AGE
  3. linkerd-service-mirror-read-remote-creds   12m

Also ensure you have permission to create Roles:

  1. $ kubectl auth can-i create Roles -n linkerd-multicluster
  2. yes

√ service mirror controller RoleBindings exist

Example error:

  1. × service mirror controller RoleBindings exist
  2.     missing RoleBindings: linkerd-service-mirror-read-remote-creds
  3.     see https://linkerd.io/checks/#l5d-multicluster-role-binding-exist for hints

Ensure that the role binding exists in service mirror controller namespace:

  1. $ kubectl get rolebinding linkerd-service-mirror-read-remote-creds -n linkerd-multicluster
  2. NAME                                       AGE
  3. linkerd-service-mirror-read-remote-creds   19m

Also ensure you have permission to create RoleBindings:

  1. $ kubectl auth can-i create RoleBindings -n linkerd-multicluster
  2. yes

√ service mirror controller ServiceAccounts exist

Example error:

  1. × service mirror controller ServiceAccounts exist
  2.     missing ServiceAccounts: linkerd-service-mirror
  3.     see https://linkerd.io/checks/#l5d-multicluster-service-account-exist for hints

Ensure that the linkerd-service-mirror service account exists:

  1. $ kubectl get ServiceAccount linkerd-service-mirror -n linkerd-multicluster
  2. NAME                     SECRETS   AGE
  3. linkerd-service-mirror   1         45m

Also ensure you have permission to create ServiceAccount:

  1. $ kubectl auth can-i create ServiceAccounts -n linkerd-multicluster
  2. yes

√ service mirror controller has required permissions

Example error:

  1. × service mirror controller has required permissions
  2.     missing Service mirror ClusterRole linkerd-service-mirror-access-local-resources: unexpected verbs expected create,delete,get,list,update,watch, got create,delete,get,update,watch
  3.     see https://linkerd.io/checks/#l5d-multicluster-local-rbac-correct for hints

This error indicates that the local RBAC permissions of the service mirror service account are not correct. In order to ensure that you have the correct verbs and resources you can inspect your ClusterRole and Role object and look at the rules section.

Expected rules for linkerd-service-mirror-access-local-resources cluster role:

  1. $ kubectl  --context=local get clusterrole linkerd-service-mirror-access-local-resources -o yaml
  2. kind: ClusterRole
  3. metadata:
  4.   labels:
  5.     linkerd.io/control-plane-component: linkerd-service-mirror
  6.   name: linkerd-service-mirror-access-local-resources
  7. rules:
  8. - apiGroups:
  9.   - ""
  10.   resources:
  11.   - endpoints
  12.   - services
  13.   verbs:
  14.   - list
  15.   - get
  16.   - watch
  17.   - create
  18.   - delete
  19.   - update
  20. - apiGroups:
  21.   - ""
  22.   resources:
  23.   - namespaces
  24.   verbs:
  25.   - create
  26.   - list
  27.   - get
  28.   - watch

Expected rules for linkerd-service-mirror-read-remote-creds role:

  1. $ kubectl  --context=local get role linkerd-service-mirror-read-remote-creds -n linkerd-multicluster  -o yaml
  2. kind: Role
  3. metadata:
  4.   labels:
  5.     linkerd.io/control-plane-component: linkerd-service-mirror
  6.   name: linkerd-service-mirror-read-remote-creds
  7.   namespace: linkerd-multicluster
  8.   rules:
  9. - apiGroups:
  10.   - ""
  11.   resources:
  12.   - secrets
  13.   verbs:
  14.   - list
  15.   - get
  16.   - watch

√ service mirror controller can access remote clusters

Example error:

  1. × service mirror controller can access remote clusters
  2.     Problematic clusters:
  3.         * cluster: [remote]: Insufficient Service permissions: expected get,list,watch, got list,watch
  4.     see https://linkerd.io/checks/#l5d-smc-remote-remote-clusters-access for hints

In case you get an error of that nature you need to ensure that the ClusterRole in the remote cluster has sufficient permissions for the service mirroring controller to work correctly:

  1. $ kubectl --context=remote get  clusterrole linkerd-service-mirror-remote-access  -n linkerd-multicluster -o yaml
  2. kind: ClusterRole
  3. metadata:
  4.   name: linkerd-service-mirror-remote-access
  5. rules:
  6. - apiGroups:
  7.   - ""
  8.   resources:
  9.   - services
  10.   verbs:
  11.   - get
  12.   - list
  13.   - watch
  14. - apiGroups:
  15.   - ""
  16.   resourceNames:
  17.   - linkerd-config
  18.   resources:
  19.   - configmaps
  20.   verbs:
  21.   - get

√ all remote cluster gateways are alive

Example error:

  1. × all remote cluster gateways are alive
  2.     Some gateways are not alive:
  3.         * cluster: [remote], gateway: [linkerd-multicluster/linkerd-gateway]
  4.     see https://linkerd.io/checks/#l5d-multicluster-remote-gateways-alive

If you get such an error, you might want to check the logs of your cluster gateway on the remote cluster by running:

  1. kubectl --context=remote  logs <linkerd-gatewa-pod>  nginx  -n linkerd-multicluster  -f

Additionally it is worth checking the logs of the proxy for any errors:

  1. kubectl --context=remote  logs <linkerd-gatewa-pod>  proxy  -n linkerd-multicluster  -f

√ clusters share trust anchors

Example errors:

  1. × clusters share trust anchors
  2.     Problematic clusters:
  3.         * remote
  4.     see https://linkerd.io/checks/#l5d-multicluster-clusters-share-anchors for hints

The error above indicates that your trust anchors are not compatible. In order to fix that you need to ensure that both your anchors contain identical sets of certificates.

  1. × clusters share trust anchors
  2.     Problematic clusters:
  3.         * remote: cannot parse trust anchors
  4.     see https://linkerd.io/checks/#l5d-multicluster-clusters-share-anchors for hints

Such an error indicates that there is a problem with your anchors on the cluster named remote You need to make sure the identity config aspect of your Linkerd installation on the remote cluster is ok. You can run check against the remote cluster to verify that:

  1. linkerd --context=remote check

√ multicluster daisy chaining is avoided

Example errors:

  1. ‼ multicluster daisy chaining is avoided
  2.     * mirror service backend-one-svc-remote.multicluster-test is exported
  3.     see https://linkerd.io/checks/#l5d-multicluster-daisy-chaining for hints

This error indicates that a mirror service has been exported, causing a “daisy chain” where requests can come in to the cluster through the local gateway and be immediately sent out of the cluster to a target gateway. If the target gateway is in the source cluster, this can create an infinite loop.

Similarly, if an exported service routes to a mirror service by a traffic split, the same daisy chain effect occurs.

√ all mirror services have endpoints

Example errors:

  1. ‼ all mirror services have endpoints
  2.     Some mirror services do not have endpoints:
  3.   voting-svc-gke.emojivoto mirrored from cluster [gke] (gateway: [linkerd-multicluster/linkerd-gateway])
  4.     see https://linkerd.io/checks/#l5d-multicluster-services-endpoints for hints

The error above indicates that some mirror services in the source cluster do not have associated endpoints resources. These endpoints are created by the Linkerd service mirror controller when creating a mirror service with endpoints values as the remote gateway’s external IP.

Such an error indicates that there could be a problem with the creation of the mirror resources by the service mirror controller or the mirror gateway service in the source cluster or the external IP of the gateway service in target cluster.

√ all gateway mirrors have endpoints

Example errors:

  1. ‼ all gateway mirrors have endpoints
  2.     Some gateway mirrors do not have endpoints:
  3.   linkerd-gateway-gke.linkerd-multicluster mirrored from cluster [gke]
  4.     see https://linkerd.io/checks/#l5d-multicluster-gateways-endpoints for hints

The error above indicates that some gateway mirror services in the source cluster do not have associated endpoints resources. These endpoints are created by the Linkerd service mirror controller on the source cluster whenever a link is established with a target cluster.

Such an error indicates that there could be a problem with the creation of the resources by the service mirror controller or the external IP of the gateway service in target cluster.

√ all referenced/cluster gateways are valid

This check is used to validate gateways. These are performed perform both at the source cluster using the kube-configs of the linked remote clusters, and also at the target cluster directly(if there are any exported services present).

Example errors:

  1. ‼ remote: all referenced gateways are valid
  2.     * southeastasia: remote cluster has invalid gateways:
  3.       Exported service web-svc.emojivoto references a gateway with no external IP: linkerd-gateway.linkerd-multicluster
  4.       Exported service web-svc.emojivoto references a gateway that is missing port mc-gateway: linkerd-gateway.linkerd-multicluster
  5.     * gke-two: remote cluster has invalid gateways:
  6.       Exported service voting-svc.emojivoto references a gateway that does not exist: linkerd-gateway.linkerd-multicluster
  7.     see https://linkerd.io/checks/#l5d-multicluster-gateways-exist for hints

A gateway is considered valid if it exists, has a external IP, and does not have any mis-configured ports.

A Linkerd gateway service should have the following ports exposed i.e mc-gateway and mc-probe, which are used to pass requests and check health respectively.

  1. ‼ all cluster gateways are valid
  2.     Some gateway services do not have endpoints:
  3.     linkerd-gateway.linkerd-multicluster
  4.     see https://linkerd.io/checks/#l5d-multicluster-gateways-exist for hints

If the check is performed on the target cluster, It also reports if the relevant endpoints resource for the gateway service is absent.