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66 lines
2.9 KiB
Plaintext
66 lines
2.9 KiB
Plaintext
// Module included in the following assemblies:
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//
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// * installing/installing_with_agent_bases_installer/preparing-to-install-with-agent-based-installer.adoc
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:_content-type: CONCEPT
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[id="understanding-agent-install_{context}"]
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= Understanding Agent-based Installer
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As an {product-title} user, you can leverage the advantages of the Assisted Installer hosted service in disconnected environments.
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The Agent-based installation comprises a bootable ISO that contains the Assisted discovery agent and the Assisted Service. Both are required to perform the cluster installation, but the latter runs on only one of the hosts.
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The `openshift-install agent create image` subcommand generates an ephemeral ISO based on the inputs that you provide. You can choose to provide inputs through the following manifests:
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Preferred:
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* `install-config.yaml`
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* `agent-config.yaml`
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or
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Optional: ZTP manifests
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* `cluster-manifests/cluster-deployment.yaml`
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* `cluster-manifests/agent-cluster-install.yaml`
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* `cluster-manifests/pull-secret.yaml`
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* `cluster-manifests/infraenv.yaml`
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* `cluster-manifests/cluster-image-set.yaml`
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* `cluster-manifests/nmstateconfig.yaml`
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* `mirror/registries.conf`
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* `mirror/ca-bundle.crt`
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[id="agent-based-installer-workflow"]
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== Agent-based Installer workflow
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One of the control plane hosts runs the Assisted Service at the start of the boot process and eventually becomes the bootstrap host. This node is called the *rendezvous host* (node 0).
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The Assisted Service ensures that all the hosts meet the requirements and triggers an {product-title} cluster deployment. All the nodes have the Red Hat Enterprise Linux CoreOS (RHCOS) image written to the disk. The non-bootstrap nodes reboot and initiate a cluster deployment.
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Once the nodes are rebooted, the rendezvous host reboots and joins the cluster. The bootstrapping is complete and the cluster is deployed.
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.Node installation workflow
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image::agent-based-installer-workflow.png[Agent-based installer workflow]
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You can install a disconnected {product-title} cluster through the `openshift-install agent create image` subcommand for the following topologies:
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* **A single-node {product-title} cluster (SNO)**: A node that is both a master and worker.
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* **A three-node {product-title} cluster** : A compact cluster that has three master nodes that are also worker nodes.
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* **Highly available {product-title} cluster (HA)**: Three master nodes with any number of worker nodes.
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== Recommended resources for topologies
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Recommended cluster resources for the following topologies:
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.Recommended cluster resources
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[options="header"]
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|====
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|Topology|Number of master nodes|Number of worker nodes|vCPU|Memory|Storage
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|Single-node cluster|1|0|8 vCPU cores|16GB of RAM| 120GB
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|Compact cluster|3|0 or 1|8 vCPU cores|16GB of RAM|120GB
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|HA cluster|3|2 and above |8 vCPU cores|16GB of RAM|120GB
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|====
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The following platforms are supported:
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* `none`
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* `baremetal`
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* `vsphere`
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