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Chapter 13. Virtualization
virt-viewer supports direct access to RHEV-H virtual machines
It is now possible to use the Red Hat Enterprise Virtualization Hypervisor to access virtual machines directly using virt-viewer.
Hot-swappable CD images
Using the remote-viewer tool to connect to an ovirt:// URI now displays a menu that allows the user to change the CD image inserted in the virtual machine (VM). This makes it possible to change the inserted CD while the VM is running without the need to use Red Hat Enterprise Virtualization or the oVirt portal.
New package: rest
The rest package has been added to this release as a dependency of the libgovirt package. The libgovirt package allows the remote-viewer tool to connect to virtual machines managed by oVirt and Red Hat Enterprise Virtualization.
qemu-img supports preallocation with fallocate()
The qemu-img tool now includes the fallocate() system call to improve performance of the
preallocation=fulloption. To use the fallocate() system call, specify
preallocation=fallocwhen creating a qcow2 image with qemu-img. The preallocation operation runs significantly faster with
preallocation=fallocspecified, thus shortening the time necessary to prepare a new guest.
kvm-clock correctly synchronizes VM system time after suspend
KVM virtual machines use the kvm-clock utility as the time source that synchronizes the virtual machine system time with the host system time after resuming from suspend mode. Previously, in some cases when a virtual machine running on a Red Hat Enterprise Linux 6 host was suspended to disk and then restored, the virtual machine's system time did not correctly synchronize with the host system time. With this update, kvm-clock has been modified to reliably synchronize with the system time on the host.
qemu-kvm supports virtual machine shutdown trace events
Support has been added for qemu-kvm trace events during the virtual machine system shutdown process, which allows users to get detailed diagnostics about a guest system's shutdown requests issued by the
virsh shutdowncommand or by the virt-manager application. This provides users with enhanced capabilities for isolating and debugging KVM guest problems during shutdown.
qemu-kvm supports directsync cache mode on virtual disks
With this update, qemu-kvm supports the
cache=directsyncoption in the host file, which enables the use of the directsync cache mode on virtual disks. When
cache=directsyncis set on the virtual disk (configured in the guest XML or the virt-manager application), write operations on the virtual machine are only completed when data is safely on the disk. This increases data security during file transactions between virtual machines, and also improves performance by allowing I/O from the guest to bypass the host page cache.
virt-who supports encrypted passwords
Support for encrypted passwords has been added to the virt-who service. Previously, the passwords for external services were stored in the configuration file as plain text, which exposed the password to any user with read privileges. This update introduces the virt-who-password utility, which allows encrypted passwords to be stored in the virt-who configuration file. With this change, all users who open the virt-who configuration file will see the passwords as encrypted. The encrypted passwords can be decrypted by the root user.
virt-who supports offline mode
The virt-who service can now report the association between host physical machines and guest virtual machines when the hypervisor is offline, and thus no longer requires connection to the hypervisor to perform this operation. When the virt-who service cannot connect to the hypervisor, due to security policies, for example, users can now obtain information about the host-guest mapping file by using the
virt-who --printcommand, which displays the information saved in the mapping file, and sends it to the Subscription Manager.
virt-who supports host filtering
With this update, the virt-who service introduces a filtering mechanism for the Subscription Manager reports. As a result, users can now choose which hosts virt-who should display according to the specified parameters. For example, hosts that do not run any Red Hat Enterprise Linux guests, or hosts that run guests of a specified version of Red Hat Enterprise Linux.
virt-who supports cluster filtering
With this update, the virt-who service introduces a filtering mechanism for the Subscription Manager reports. As a result, users can now choose which clusters virt-who should display according to the specified parameters. For example, hosts that do not run any Red Hat Enterprise Linux guests, or hosts that run guests of a specified version of Red Hat Enterprise Linux.
virt-who supports filtering non-RHEL hypervisors
In cases where it is not necessary to report all the hypervisors, such as those that do not have any associated Red Hat Enterprise Linux guests, virt-who is now capable of filtering out the specified hypervisors.