Add Explanation for Certificate Refreshes (#637)

This commit adds an Explanation for Certificate Refreshes

docs/src/snap/explanation/certificates.md

@@ -0,0 +1,59 @@
+# Certificates
+
+Certificates are a crucial part of Kubernetes' security infrastructure, serving
+to authenticate and secure communication within the cluster. They play a key
+role in ensuring that communication between various components (such as the
+API server, kubelets, and the datastore) is both encrypted and restricted to
+authorised components only.
+
+In Kubernetes, [X.509][] certificates are primarily used for
+[Transport Layer Security][] (TLS), securing the communication between the
+cluster's components.
+
+## What Is a Certificate Refresh?
+
+A certificate refresh in {{product}} refers to the process of renewing or
+rotating certificates before they expire. Kubernetes certificates have
+a specific validity period, after which they expire and are no longer
+considered valid. Expired certificates lead to failures in communication
+between cluster components, potentially disrupting the functionality of the
+entire cluster.
+
+Regular certificate refreshes ensure that the certificates in use are valid and
+secure, preventing unauthorised access or communication failures.
+
+## Importance of Certificate Refreshes
+
+Regularly refreshing certificates in Kubernetes is essential for maintaining
+the reliability of the cluster. Here are some reasons why certificate refreshes
+are important:
+
+### Maintaining Cluster Security
+
+Certificates are crucial for securing Kubernetes clusters, ensuring encrypted
+and authenticated communication between components. If a certificate expires
+and isn't promptly renewed, it can leave the cluster vulnerable to security
+risks, potentially exposing it to unauthorised access. Regular certificate
+refreshes prevent this by ensuring only valid certificates are used,
+maintaining the cluster's security.
+
+### Preventing Downtime
+
+Kubernetes relies on certificates for internal communication between critical
+components, such as the kubelet, API server, and datastore. Expired
+certificates can hinder this communication, leading to potential downtime and
+workload disruptions. Proactively refreshing certificates before they expire
+helps maintain uninterrupted cluster operations.
+
+### Security Compliance
+
+Security standards, such as [CIS][], often require the regular rotation of
+credentials, including certificates. Periodically renewing Kubernetes
+certificates ensures that the cluster meets security standards and compliance
+requirements.
+
+<!-- LINKS -->
+
+[CIS]: https://www.cisecurity.org/controls
+[Transport Layer Security]: https://datatracker.ietf.org/doc/html/rfc8446
+[X.509]: https://datatracker.ietf.org/doc/html/rfc5280

docs/src/snap/explanation/index.md

@@ -12,6 +12,7 @@ Overview <self>
 ```{toctree}
 :titlesonly:
 about
+certificates
 channels
 clustering
 ingress