github.com/openshift/installer@v1.4.17/docs/user/agent/agent-services.md (about)

     1  # Agent-based Installer Services
     2  
     3  ## Automated Flow
     4  
     5  ![Automated Flow](./agent_installer_services-automated_flow.png)
     6  
     7  In the automated flow, all information needed to configure a cluster is included in the agent ISO.
     8  When the agent ISO is booted, agent-tui and nmstate libraries are copied to the host from initrd. This copy 
     9  step is required because the agent-tui and nmstate libraries are too big to fit into the Ignition config.
    10  
    11  * agent-interactive-console - checks the host has connectivity to the release image
    12  * agent - takes host inventory and performs validations and reports results back to assisted-service
    13  * selinux - updates the SELinux policy to allow chronyd access to container files and UNIX datagram socket 
    14  * pre-network-manager-config - applies any network configs before NetworkManager is started
    15  * set-hostname - sets the hostname if one was specified for the host in agent-config.yaml
    16  * node-zero - determines if the current host is the rendezvous host or node zero
    17  * assisted-service-pod - pod containing the assisted-service REST-API and database
    18  * assisted-service - assisted-service REST-API
    19  * assisted-service-db - postgresql database where assisted-service stores data
    20  * agent-register-cluster - reads the ZTP manifests located at /etc/assisted/manifests and registers the cluster
    21  * agent-register-infraenv - reads the ZTP manifests located at /etc/assisted/manifests and registers the infraenv
    22  * install-status - determines the current install status and writes it out to /etc/issue.d/
    23  * apply-host-config - applies root device hints and roles specified in agent-config.yaml
    24  * start-cluster-installation - calls assisted-service REST-API to start cluster installation when all hosts are in ready state and have passed validations
    25  
    26  ## Appliance flow using unconfigured ignition and config image
    27  
    28  ![Appliance Flow](./agent_installer_services-unconfigured_ignition_and_config_image_flow.png)
    29  
    30  In the appliance flow, most of the cluster deployment information is included in a config image that is mounted
    31  onto the host running the unconfigured-ignition. The appliance flow does not include the agent-tui or the
    32  agent-interactive-console service because the disk images generated in the factory contains the release payload
    33  so no connectivity checks to the release image is needed.
    34  
    35  * load-config-iso@ - detects the config image has been mounted and copies the cluster configuration files from the config image to the host. It also enables start-cluster-installation which is disabled by default in the unconfigured-ignition. The actual service is created when the config image is mounted as a device and its name will be load-config-iso@<dev-name>.service e.g load-config-iso@-dev-sr1.service
    36  * agent-check-config-image - if the config image has not been mounted, it displays a message to the console asking for the config image to be mounted in order to start the cluster installation.