You can use Update Manager to perform orchestrated upgrades of the ESX/ESXi hosts in your vSphere inventory by using a single upgrade baseline.
This workflow describes the overall process to perform an orchestrated upgrade of the hosts in your vSphere inventory.
You can perform orchestrated upgrades of hosts at the folder, cluster, or datacenter level.
Update Manager 5.5 supports upgrade from ESXi 4.x, ESXi 5.0 and ESXi 5.1 to ESXi 5.5 and migration from ESX 4.x to ESXi 5.5. You cannot use Update Manager to upgrade a host to ESXi 5.5 if the host was upgraded from ESX 3.x to ESX 4.x. Such hosts do not have sufficient free space in the /boot partition to support the Update Manager upgrade process. Use a scripted or interactive upgrade instead.
After you have upgraded or migrated your host to ESXi 5.5, you cannot roll back to your version ESX/ESXi 4.x, ESXi 5.0 or ESXi 5.1 software. Back up your host configuration before performing an upgrade or migration. If the upgrade or migration fails, you can reinstall the ESX/ESXi 4.x, ESXi 5.0 or ESXi 5.1 software that you upgraded or migrated from, and restore your host configuration. For more information about backing up and restoring your ESX/ESXi configuration, see vSphere Upgrade.
Configure the Update Manager host and cluster settings.
You can configure the Update Manager settings from the Configuration tab of the Update Manager Administration view. For more information and the detailed procedures about configuring host and cluster settings by using Update Manager, see Configuring Host and Cluster Settings.
Import an ESXi image (which is distributed as an ISO file) and create a host upgrade baseline.
Import an ESXi 5.5 image so that you can upgrade the hosts in your vSphere inventory. You can import a host image from the ESXi Images tab of the Update Manager Administration view.
For the complete procedure about importing host upgrade releases, see Import Host Upgrade Images and Create Host Upgrade Baselines.
Attach the host upgrade baseline to a container object containing the hosts that you want to upgrade.
You can attach baselines and baseline groups to objects from the Update Manager Compliance view. For more information about attaching baselines and baseline groups to vSphere objects, see Attach Baselines and Baseline Groups to Objects.
Scan the container object.
After you attach baselines to the selected container object, you must scan it to view the compliance state of the hosts in the container. You can scan selected objects manually to start the scanning immediately. For detailed instructions on how to scan your hosts manually, see Manually Initiate a Scan of ESX/ESXi Hosts.
You can also scan the hosts in the container object at a time convenient for you by scheduling a scan task. For more information and detailed instructions about scheduling a scan, see Schedule a Scan.
Review the scan results displayed in the Update Manager Client Compliance view.
For a detailed procedure about viewing scan results and for more information about compliance states, see Viewing Scan Results and Compliance States for vSphere Objects.
Remediate the container object.
If hosts are in Non-Compliant state, remediate the container object of the hosts to make it compliant with the attached baseline. You can start the remediation process manually or schedule a remediation task. For more information about remediating hosts against an upgrade baseline and for a detailed procedure, see Remediate Hosts Against an Upgrade Baseline.
Hosts that are upgraded reboot and disconnect for some time during the remediation.