etcd CA 証明書は、Kubernetes API サーバーから etcd レプリカへの通信と、etcd レプリカ間の通信を保護します。この証明書は自己署名によるものです。
クラスタ CA 証明書は、Kubernetes API サーバーとすべての内部 Kubernetes API クライアント（kubelet、コントローラ マネージャー、スケジューラなど）間の通信を保護します。この証明書は自己署名によるものです。
フロントプロキシ CA 証明書は、集約 API との通信を保護します。この証明書は自己署名によるものです。
証明書のローテーションは、gkectl を使用してトリガーできます。ローテーションの際、gkectl によって管理クラスタのコアシステムの CA 証明書が新しく生成された証明書に置き換えられます。その後、新しい CA 証明書、リーフ証明書、秘密鍵が管理クラスタのシステム コンポーネントに配布されます。ローテーションは段階的に行われるため、システム コンポーネントはローテーション中も通信を継続できます。ただし、ローテーション中にワークロードとノードが再起動されることに注意してください。
CA が正常にローテーションされると、コマンドが終了し、新しい kubeconfig ファイルが自動的に生成されます。コマンドで指定した kubeconfig ファイルが新しいファイルに置き換えられます。コマンドの出力は次のようになります。
Beginning CA rotation with generated CA
...
Successfully rotated CA for admin cluster. The kubeconfig file
"/home/ubuntu/kubeconfig" has been updated.
Done rotating certificate-authorities
[[["わかりやすい","easyToUnderstand","thumb-up"],["問題の解決に役立った","solvedMyProblem","thumb-up"],["その他","otherUp","thumb-up"]],[["わかりにくい","hardToUnderstand","thumb-down"],["情報またはサンプルコードが不正確","incorrectInformationOrSampleCode","thumb-down"],["必要な情報 / サンプルがない","missingTheInformationSamplesINeed","thumb-down"],["翻訳に関する問題","translationIssue","thumb-down"],["その他","otherDown","thumb-down"]],["最終更新日 2025-09-04 UTC。"],[],[],null,["Google Distributed Cloud use certificates and private keys to authenticate\ncommunication between Kubernetes system components in an admin cluster. When you\ncreate an admin cluster, new certificate authority (CA) certificates are created,\nand these root certificates are used to issue additional leaf certificates for\nKubernetes system components.\n\nThis guide applies only to rotation of admin cluster CA certificates. For\nuser clusters, see\n[Rotating user cluster CA certificates](/kubernetes-engine/distributed-cloud/vmware/docs/how-to/ca-rotation).\n\nThere are three CA certificates used by the Kubernetes system in an admin\ncluster:\n\n- The etcd CA certificate secures communication from the Kubernetes API server\n to the etcd replicas and also communication between etcd replicas. This\n certificate is self-signed.\n\n- The cluster CA certificate secures communication between the Kubernetes API\n server and all internal Kubernetes API clients, for example, the kubelet, the\n controller manager, and the scheduler. This certificate is self-signed.\n\n- The front-proxy CA certificate secures communication with\n [aggregated APIs](https://kubernetes.io/docs/concepts/extend-kubernetes/api-extension/apiserver-aggregation/).\n This certificate is self-signed.\n\nYou can use `gkectl` to trigger a certificate rotation. During a rotation,\n`gkectl` replaces the core system CA certificates for the\nadmin cluster with newly generated certificates. Then it distributes the new\nCA certificates, leaf certificates, and private keys to admin cluster system\ncomponents. The rotation happens incrementally, so that system components can\ncontinue to communicate during the rotation. Note, however, that workloads and\nnodes are restarted during the rotation.\n\nWithout rotation, CA certificates and control-plane certificates will expire\nfive years from the date the cluster was created. The control plane certificates\nare automatically rotated during a cluster upgrade, but the CAs are\nnot automatically rotated. This means a CA rotation must be performed at least\nonce every five years, in addition to regular version upgrades.\n| **Warning:** A CA certificate rotation revokes the old CA certificates at the end of the operation. This invalidates kubeconfig files that were based on an old certificate. Consequently, the credentials in the kubeconfig file stop working after a CA certificate rotation. This guide includes instructions on how to update your kubeconfig file. The same issue applies to authentication configuration files.\n\nLimitations\n\n- Note the following limitation with advanced clusters:\n\n - Version 1.31: CA rotation isn't supported on [advanced clusters](/kubernetes-engine/distributed-cloud/vmware/docs/how-to/admin-cluster-configuration-file-latest#enable-advanced-cluster-field).\n - Version 1.32 and higher: CA rotation is supported on advanced clusters but there are some minor differences noted where applicable in this document.\n- CA certificate rotation limited to the etcd, cluster, and front-proxy\n certificates mentioned previously.\n\n- CA certificate rotation is limited to certificates issued automatically by\n Google Distributed Cloud. It does not update certificates issued manually by an\n administrator, even if those certificates are signed by the system CAs.\n\n- CA certificate rotation restarts the Kubernetes API server, other\n control-plane processes, and each node in the admin cluster multiple times.\n Each stage of a rotation progresses similarly to a cluster upgrade. While the\n admin cluster and the user clusters managed by the admin cluster do remain\n operational during a certificate rotation, you should expect that workloads\n in the admin cluster will be restarted and rescheduled. You should also expect\n brief periods of downtime for the admin cluster control plane and user cluster\n control plane.\n\n- You must update the admin cluster kubeconfig file in the middle of a\n certificate rotation and again after the rotation completes. This is because\n the old cluster certificate is revoked, and the credentials in the kubeconfig\n file will no longer work.\n\n- Once initiated, a CA certificate rotation cannot be rolled back.\n\n- A CA certificate rotation might take considerable time to complete, depending\n on the size of the cluster.\n\n- The certificate rotation process can be resumed by re-running the same\n command if it is interrupted. However, you must ensure that there is only one\n rotation command running at a time.\n\nStart the rotation\n\nTo start the certificate rotation, run the following command:\n\n```\ngkectl update credentials certificate-authorities rotate \\\n --admin-cluster \\\n --config ADMIN_CLUSTER_CONFIG \\\n --kubeconfig ADMIN_CLUSTER_KUBECONFIG\n```\n\nReplace the following:\n\n- \u003cvar translate=\"no\"\u003eADMIN_CLUSTER_CONFIG\u003c/var\u003e: the path of the admin cluster configuration\n file\n\n- \u003cvar translate=\"no\"\u003eADMIN_CLUSTER_KUBECONFIG\u003c/var\u003e: the path of the admin cluster kubeconfig\n file\n\nThe behavior of the command differs depending on whether advanced cluster\nis enabled: \n\nNot enabled\n\nThe `gkectl update credentials certificate-authorities rotate` command starts\nand performs the first half of the rotation. The command then pauses to let\nyou run the next command to update the kubeconfig file.\n\nUpdate the kubeconfig file\n\nWhen the `gkectl update credentials certificate-authorities rotate` command\npauses, update the kubeconfig file for the admin cluster. This places a new\nclient certificate and a new CA certificate in the kubeconfig file. The old\nclient certificate is removed from the kubeconfig file, and the old CA\ncertificate remains in the kubeconfig file.\n\n```\ngkectl update credentials certificate-authorities update-kubeconfig \\\n --admin-cluster \\\n --config ADMIN_CLUSTER_CONFIG \\\n --kubeconfig ADMIN_CLUSTER_KUBECONFIG\n```\n\nContinue the rotation\n\nRun the following command to perform the second half of the procedure. The\ncommand doesn't proceed until `gkectl` verifies that the updated kubeconfig\nfile is in the current directory.\n\n```\ngkectl update credentials certificate-authorities rotate \\\n --admin-cluster \\\n --complete \\\n --config ADMIN_CLUSTER_CONFIG \\\n --kubeconfig ADMIN_CLUSTER_KUBECONFIG\n```\n\nWhen the rotation is complete, it reports the current CA version.\n\nUpdate the kubeconfig file again\n\nAfter the second half of the rotation completes, update the kubeconfig file\nagain. This removes the old CA certificate from the kubeconfig file.\n\n```\ngkectl update credentials certificate-authorities update-kubeconfig \\\n --admin-cluster \\\n --config ADMIN_CLUSTER_CONFIG \\\n --kubeconfig ADMIN_CLUSTER_KUBECONFIG\n```\n\nEnabled\n\nIf advanced cluster is enabled, the `gkectl update credentials\ncertificate-authorities rotate` command is synchronous. The command outputs\nstatus messages to the admin workstation as the CA rotation progresses.\n\nAfter the CA is rotated successfully, the command exits and a new kubeconfig\nfile is automatically generated. The kubeconfig file that you specified in the\ncommand is replaced with a new one. The command output is similar to the\nfollowing:\n\n```\nBeginning CA rotation with generated CA\n...\nSuccessfully rotated CA for admin cluster. The kubeconfig file\n\"/home/ubuntu/kubeconfig\" has been updated.\nDone rotating certificate-authorities\n```\n\nDistribute the new kubeconfig file\n\nDistribute the new admin cluster kubeconfig file to all cluster users."]]
