Template maintenance

A template can be put into to a special mode called "maintenance", which is primarily used to update or install software in the guest operating system. While in this mode, the template becomes unavailable for all normal tasks, including creating new guest VMs, and it becomes possible to start it as a regular virtual machine. Once the virtual machine is running, you can install or update software in the guest OS or perform administrative tasks in the operating system.

Depending on whether a template is configured for full or linked clones, the maintenance mode is used slightly differently, as described below.

Full clones

If your template is configured to create full clones, do the following:

1. Select a template and click Tasks > Maintenance. The template becomes disabled (grayed out) and all operations on it are suspended. The status of template in the Status column changes to "Entering maintenance" and when completed, changes to "Maintenance".
2. Using native tools of the hypervisor, start the template as a normal virtual machine.
3. Install Windows updates or software as necessary.
4. When done, shut down the virtual machine.
5. Back in the RAS Console, select the template and click Tasks > Maintenance again to exit the maintenance mode. The status of exiting maintenance is also displayed at the bottom of the window.
6. At this point, you may see a message asking whether you would like to recreate existing guest VMs. The message is displayed when there's one or more existing guest VMs that were already created from this template. When you update a full clone template, the changes will only affect future clones. For existing clones to have these updates, they must be recreated. You can choose to recreate existing guest VMs now or you can postpone it. Please note that recreating a full clone is a time consuming process. Also, a new app may be installed in a full clone VM or a user profile may be changed while the recreation is in progress, all of which will be lost. To minimize impact on users, it makes sense to schedule a maintenance window during which the clones can be recreated.

Linked clones

Since linked clones share the virtual hard disk with a snapshot of a template, you need to take additional steps compared to full clones.

First, you need to notify guest VM users to save their data and log off. This is necessary for existing guest VMs to include the updates that you will install in the template. Once all users are logged off, do the following:

1. Select a template and click Tasks > Maintenance. The template becomes disabled (grayed out) and all operations on it are suspended. The status of the operation is displayed at the bottom of the window.
2. Using native tools of the hypervisor, start the template as a normal virtual machine.
3. Install Windows updates or software as necessary.
4. When done, shut down the virtual machine.
5. Back in the RAS Console, select the template and click Tasks > Maintenance again to exit the maintenance mode. A dialog is displayed asking if you would like to recreate existing guest VMs. If you click No, then the dialog is closed and the existing guest VMs are left in their current state, which means that the updates that you installed will not appear in the existing VMs. If you click Yes, read on.
6. If you click Yes in the previous step, existing guest VMs will be examined for active connections. If an active connection exists, another dialog opens asking if you want to proceed:
   • If you click Yes, all active sessions are forcibly logged off and existing guest VMs (linked clones), together with the corresponding snapshot, are deleted and a new snapshot and VMs are created from the updated template.
   • If you click No, the Template Guest VMs List dialog opens where you can view the current state of each available guest VM. The dialog gives you control over a guest VM. You can send a message to the user and you can log the user off. Once all active sessions are logged off, click OK. The existing guest VMs and the corresponding snapshot are deleted and a new snapshot and VMs are created from the updated template.

When you are done configuring a template, click the Apply button on the main RAS Console window to commit the changes to Parallels RAS.

Please note that if you leave the maintenance mode without recreating linking clones, you will have to enter the maintenance mode again to apply the updates.

Updating RAS Guest Agent inside a template

A template must have the latest version of RAS Guest Agent installed in it. The agent is installed when you create a template. When a new version of RAS Guest Agent becomes available, it should be updated. To update the agent, the maintenance mode must be used as described above. To simplify agent updates, Parallels RAS monitors all installed agents and notifies the administrator when an update is available.

When the RAS Console starts, all installed agents are checked and a message is displayed if one or more agents need to be updated. This applies to servers in the RAS infrastructure and the templates. The message will ask if you want to update all agents. If you click Yes, you are presented with a dialog listing all servers and templates on which an agent needs to be updated. You can select or un-select a server/template to include it in the bulk update procedure or exclude it. Once you've made your selection, click OK to start the update. Follow the onscreen instructions and update the agents.

Full vs. linked clone templates: When you update RAS Guest Agent in a template, you also need to update Agents in guest VMs that were created from this template. This update is done differently for full and linked clone templates. Please read the instructions below for the explanation.

When you update the Agent in a linked clone template, you'll be asked if you want to recreate all guest VMs that were created from this template. You can click Yes and they will be automatically recreated to match the template.

When you update the Agent in a full clone template, full clone guest VMs are not automatically recreated. You will be asked if you want to recreate them. If you decide to do so, please note that full clone VMs are complete machines, so recreating them is a time-consuming process. Alternatively, you can update the agent in these VMs by push-installing it from the RAS Console. This can be done by clicking Tasks > Upgrade all Agents while on the VDI > Desktops tab.

To manually check the RAS Guest Agent status in a template, click Tasks > Check agent. If the agent is up to date, a message box is displayed confirming this. If a newer version of RAS Guest Agent is available, you'll see a dialog asking you to update it. Please note that the difference in updating full and linked clone templates (as described above) applies to this scenario as well.

Maintaining RD Session Hosts based on a template

If you need to do a scheduled maintenance of RD Session Hosts that were created from a template, please follow these steps:

1. Create a schedule that fits your maintenance window to drain a desired RD Session Host group.
2. During maintenance (or right before it) switch the template into maintenance mode. Then apply the necessary changes.
3. The schedule disables groups provisioned by the template (while the maintenance window lasts) which leads to removing (unassigning) all guest VMs from them.
4. Release the template from maintenance and click Yes when asked whether to recreate all clones.
5. Enable groups which were disabled in step 3 (above). At this point, the groups will begin receiving guest VMs to comply with Keep Available Buffer setting
6. From this point forward, groups are provisioned with VMs on demand.