Red Hat Virtualization

Objectives

After completing this section, you should be able to change the configuration of virtual hardware for an existing virtual machine.

Editing a Virtual Machine

To persistently change the settings of a virtual machine, navigate to the list of virtual machines by clicking Compute in the menu bar, and then selecting Virtual Machines. Right-click the virtual machine and select Edit from the menu. This brings up the Edit Virtual Machine window.

Figure 8.2: Edit Virtual Machine window

The Edit Virtual Machine window is nearly identical to the New Virtual Machine window, discussed earlier. In order to see all of the settings, you will need to click the Show Advanced Options button. Please note that some changes require that the virtual machine is shut down and restarted. You will be alerted if a shutdown is required; when viewing the list of virtual machines, the impacted virtual machine will be marked with an orange pending changes icon.

The following section describes some of the main tabs in the New Virtual Machine window, and the types of changes you might make within them.

Configuring Virtual NUMA

In the Administration Portal, you can configure virtual non-uniform memory access (NUMA) nodes on a virtual machine, and pin them to physical NUMA nodes on one or more hosts. This can be done from the Host tab when viewing Show Advanced Options in either the New Virtual Machine window, or the Edit Virtual Machine window. The default policy is to schedule and run virtual machines on any available resources on the host. As a result, resources backing a large virtual machine that cannot fit within a single host socket could be spread out across multiple NUMA nodes. Over time these resources may be moved around, leading to poor and unpredictable performance. Configure and pin virtual NUMA nodes to avoid this outcome and improve performance.

Hot-Plugging Network Interfaces and Disks

RHV allow adding network interfaces and disks to running virtual machines. This is referred to as hot-plugging. For network interfaces, it is possible to add a network interface to a virtual machine and then plug it in, or unplug it, as necessary. A plugged in network interface is accessible to the virtual machine, while an unplugged one is not. One way to view network interfaces from a Linux virtual machine is using the ip link command.

Additional hard disks can be added in a similar way. A new hard disk is accessible to the virtual machine when it is activated. A deactivated hard disk is still associated with a virtual machine, but it is not accessible by the virtual machine. One way to view hard disks from a Linux virtual machine is using the lsblk command.

Care must be taken when removing network interfaces or disks from running virtual machines to ensure that they are not being used.

Adding Network Interfaces

Virtual machines connect network interfaces to logical networks in your RHV environment. You can create multiple network interfaces on your virtual machines, each of which can be associated with a specific logical network.

A quick way of adding a new network interface is to use the same basic procedure that you used when creating the virtual machine. To add a new network interface, edit the virtual machine and go to the General tab. The Instantiate VM network interfaces by picking a vNIC profile section allows you to add new network interfaces or remove existing ones, using the + and - buttons. You cannot specifically plug or unplug a network interface from the General tab. New network interfaces added from the General tab are automatically plugged in and accessible to the virtual machine.

More options are available when you view virtual machine details by clicking the name of an individual virtual machine listed on the Compute >> Virtual Machines page. From the details page, you can click the Network Interfaces tab. Here you can either add a new network interface or select an existing network interface to edit. When adding a new network interface, in addition to selecting a VM Network profile, you can select a driver type, and you can customize the MAC address. When adding or editing a network interface, you can specify the link state as being Up or Down, and the card status as being either Plugged or Unplugged. You can edit a network interface on a running machine, but depending on the changes you make, the virtual machine might need to be restarted.

Adding Disks

New disks can be added to a virtual machine. As with network interfaces, there is a quick method and a more advanced method. The quick method uses the same basic procedure that you used when creating the virtual machine. To add a new disk, edit the virtual machine and go to the General tab. The Instance Images section allows you to add new disks or remove existing disks, using the + and - buttons. Existing disks can be modified using the Edit button.

More options are available when you view virtual machine details by clicking the name of an individual virtual machine listed on the Compute >> Virtual Machines page. From the details page, click the Disks tab. Additional configuration fields are available when you choose to add or edit a disk. To deactivate an individual disk, highlight the row containing the disk by clicking an empty cell in the row. With the row highlighted, click the three vertical dot menu, located to the right of the Remove button, and select Deactivate. A deactivated disk can be removed. When you attempt to remove a disk, you will be prompted to confirm you action. You must also decide if the disk should be removed permanently. A disk which is not removed permanently can be attached to a different virtual machine.