FAQ

Below is an aggregation of solutions to some issues that cert-manager users may face:

Certificates

Can I trigger a renewal from cert-manager at will?

This is a feature in cert-manager starting in v0.16 using the kubectl plugin. More information can be found on the renew command's page

cert-manager publishes all events to the Kubernetes events mechanism, you can get the events for your specific resources using kubectl describe <resource> <name>. Due to the nature of the Kubernetes event mechanism these will be purged after a while. If you're using a dedicated logging system it might be able or is already also storing Kubernetes events.

What happens if a renewal is doesn't happen due to issues? Will it be tried again after sometime?

cert-manager makes use of exponential back off to retry any failures on requesting or renewing certificates. It will retry any failures unless the Issuer gave a fatal error that it marked as not retryable.

Is ECC (elliptic-curve cryptography) supported?

cert-manager supports ECDSA key pairs! You can set your certificate to use ECDSA in the privateKey part of your Certificate resource. For example:

apiVersion: cert-manager.io/v1
kind: Certificate
metadata:
  name: ecdsa
spec:
  secretName: ecdsa-cert
  isCA: false
  privateKey:
    algorithm: ECDSA
    size: 256
  dnsNames:
    - ecdsa.example.com
  issuerRef:
    [...]

If `renewBefore` or `duration` is not defined, what will be the default value?

cert-manager will default to a duration of 90 days with a renewBefore of 30 days. If renewBefore is not set and the duration of the signed certificate is shorter or equal to 30 days, the renewBefore time will be set to 2/3 of the signed certificate validity duration. When setting duration it is recommended to also set renewBefore, if renewBefore is longer than duration you will receive an error.

Miscellaneous

Kubernetes has a builtin `CertificateSigningRequest` API. Why not use that?

Kubernetes has a Certificate Signing Requests API, and a kubectl certificates command which allows you to approve certificate signing requests and have them signed by the certificate authority (CA) of the Kubernetes cluster.

This API and CLI have occasionally been misused to sign certificates for use by non-control-plane Pods but this is a mistake. For the security of the Kubernetes cluster, it is important to limit access to the Kubernetes certificate authority, and it is important that you do not use that certificate authority to sign certificates which are used outside of the control-plane, because such certificates increase the opportunity for attacks on the Kubernetes API server.

In Kubernetes 1.19 the Certificate Signing Requests API has reached V1 and it can be used more generally by following (or automating) the Request Signing Process. There are plans for cert-manager make greater use of this API now that it is stable.

FAQ