Remediation is the process in which Update Manager applies patches, extensions, and upgrades to ESX/ESXi hosts, virtual machines, or virtual appliances after a scan is complete.
Remediation makes the selected vSphere objects compliant with patch, extension, and upgrade baselines.
As with scanning, you can remediate single hosts, virtual machines, or virtual appliances, and you can also initiate remediation on the folder, cluster, or datacenter level, as well as on all objects in your virtual infrastructure.
Update Manager supports remediation for the following inventory objects:
Powered on, suspended, or powered off virtual machines and templates for VMware Tools and virtual machine hardware upgrade.
Powered on virtual appliances that are created with VMware Studio 2.0 and later, for virtual appliance upgrade.
ESX/ESXi hosts for patch, extension, and upgrade remediation.
You can remediate the objects in your vSphere inventory by using either manual remediation or scheduled remediation. For more information about manual and scheduled remediation, see Remediating vSphere Objects.
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.
Update Manager neither upgrades nor patches PXE booted ESXi hosts of version 4.x and skips them when you remediate hosts in a container object. You can patch PXE booted ESXi 5.x hosts if you enable the setting from the ESX Host/Cluster Settings page of the Configuration tab or from the Remediate wizard.
After you upload ESXi images, upgrades for ESX/ESXi hosts are managed through baselines and baseline groups.
Typically hosts are put into maintenance mode before remediation if the update requires it. Virtual machines cannot run when a host is in maintenance mode. To ensure a consistent user experience, vCenter Server migrates the virtual machines to other hosts within a cluster before the host is put in maintenance mode. vCenter Server can migrate the virtual machines if the cluster is configured for vMotion and if VMware Distributed Resource Scheduler (DRS) and VMware Enhanced vMotion Compatibility (EVC) are enabled. EVC is not a prerequisite for vMotion. EVC guarantees that the CPUs of the hosts are compatible. For other containers or individual hosts that are not in a cluster, migration with vMotion cannot be performed.
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.
Remediating Virtual Machines and Virtual Appliances
You can upgrade virtual appliances, VMware Tools, and the virtual hardware of virtual machines to a later version. Upgrades for virtual machines are managed through the Update Manager default virtual machine upgrade baselines. Upgrades for virtual appliances can be managed through both the Update Manager default virtual appliance baselines and custom virtual appliance upgrade baselines that you create.
Update Manager 5.x does not support virtual machine patch baselines.
With Update Manager, you can perform orchestrated upgrades of hosts and virtual machines. Orchestrated upgrades allow you to upgrade hosts and virtual machines in your vSphere inventory by using baseline groups.
You can perform an orchestrated upgrade of hosts by using a baseline group that contains a single host upgrade baseline and multiple patch or extension baselines. Update Manager first upgrades the hosts and then applies the patch or extension baselines.
You can perform an orchestrated upgrade of virtual machines by using a virtual machine baseline group that contains the following baselines:
VM Hardware Upgrade to Match Host
VMware Tools Upgrade to Match Host
You can use orchestrated upgrades to upgrade the virtual hardware and VMware Tools of virtual machines in the inventory at the same time. The VMware Tools upgrade baseline runs first, followed by the virtual machine hardware upgrade baseline.
Orchestrated upgrades can be performed at a cluster, folder, or datacenter level.