Virtualization Getting Started Guide
An introduction to virtualization concepts
Chapter 1. General Introduction to Virtualization
1.1. What is Virtualization?
- Full virtualization
- Full virtualization uses an unmodified version of the guest operating system. The guest addresses the host’s CPU via a channel created by the hypervisor. Because the guest communicates directly with the CPU, this is the fastest virtualization method.
- Paravirtualization uses a modified guest operating system. The guest communicates with the hypervisor. The hypervisor passes the unmodified calls from the guest to the CPU and other interfaces, both real and virtual. Because the calls are routed through the hypervisor, this method is slower than full virtualization.
- Software virtualization (or emulation)
- Software virtualization uses binary translation and other emulation techniques to run unmodified operating systems. The hypervisor translates the guest calls to a format that can be used by the host system. Because all calls are translated, this method is slower than virtualization. Note that Red Hat does not support software virtualization on Red Hat Enterprise Linux.
1.2. Virtualization Solutions
- Red Hat Enterprise Linux
- The ability to create, run, and manage virtual machines, as well as a number of virtualization tools and features are included in Red Hat Enterprise Linux 7. This solution supports a limited number of running guests per host, as well as a limited range of guest types. As such, virtualization on Red Hat Enterprise Linux can be useful for example to developers who require testing in multiple environments, or to small businesses running several servers that do not have strict uptime requirements or service-level agreements (SLAs).
ImportantThis guide provides information about virtualization on Red Hat Enterprise Linux and does not go into detail about other virtualization solutions.
- Red Hat Virtualization
- Red Hat Virtualization (RHV) is based on the Kernel-based Virtual Machine (KVM) technology like virtualization on Red Hat Enterprise Linux is, but offers an enhanced array of features. Designed for enterprise-class scalability and performance, it enables management of your entire virtual infrastructure, including hosts, virtual machines, networks, storage, and users from a centralized graphical interface.
NoteFor more information about the differences between virtualization in Red Hat Enterprise Linux and Red Hat Virtualization, see the Red Hat Customer Portal.Red Hat Virtualization can be used by enterprises running larger deployments or mission-critical applications. Examples of large deployments suited to Red Hat Virtualization include databases, trading platforms, and messaging systems that must run continuously without any downtime.
NoteFor more information about Red Hat Virtualization, or to download a fully supported 60-day evaluation version, see http://www.redhat.com/en/technologies/virtualization/enterprise-virtualization. Alternatively, refer to the Red Hat Virtualization documentation suite.
- Red Hat OpenStack Platform
- Red Hat OpenStack Platform offers an integrated foundation to create, deploy, and scale a secure and reliable public or private OpenStack cloud.
NoteFor more information about Red Hat OpenStack Platform, or to download a 60-day evaluation version, see https://www.redhat.com/en/technologies/linux-platforms/openstack-platform. Alternatively, refer to the Red Hat OpenStack Platform documentation suite.
Chapter 2. Why Use Virtualization?
2.1. Virtualization Costs
- Less power
- Using virtualization negates much of the need for multiple physical platforms. This equates to less power being drawn for machine operation and cooling, resulting in reduced energy costs. The initial cost of purchasing multiple physical platforms, combined with the machines' power consumption and required cooling, is drastically cut by using virtualization.
- Less maintenance
- Provided that adequate planning is performed before migrating physical systems to virtualized ones, less time is needed to maintain them. This means less money needs to be spent on parts and labor.
- Extended life for installed software
- Older versions of software may not be able to run directly on more recent bare-metal machines. By running older software virtually on a larger, faster system, the life of the software may be extended while taking advantage of better performance from a newer system.
- Predictable costs
- A Red Hat Enterprise Linux subscription provides support for virtualization at a fixed rate, making it easy to predict costs.
- Less space
- Consolidating servers onto fewer machines means less physical space is required for computer systems.
- Red Hat Enterprise Linux 6.4 and KVM recorded an industry-leading TPC-C benchmark with an IBM DB2 database running in an entirely virtualized x86 environment and delivering 88% of bare-metal performance. Due to resource demands, databases have previously been reserved for bare-metal deployments only.
- The industry standard SAP Sales and Distribution (SD) Standard Application Benchmark found that Red Hat Enterprise Linux 6.2 and KVM performs at the virtualization efficiency of 85% when compared to a bare-metal system running on identical hardware.
- Red Hat Enterprise Linux 6.1 and KVM achieved record-setting virtualization performance in the SPECvirt_sc2010 benchmark recorded by the Standard Performance Evaluation Corporation (SPEC), setting the best virtual performance mark of any published SPECvirt result. The SPECvirt_sc2010 metric measures the end-to-end performance of system components in virtualized data center servers.
- Offline migration
- An offline migration suspends the guest virtual machine, and then moves an image of the virtual machine's memory to the destination host. The virtual machine is then resumed on the destination host and the memory used by the virtual machine on the source host is freed.
- Live migration
- Live migration is the process of migrating an active virtual machine from one physical host to another. Note that this is not possible between all Red Hat Enterprise Linux releases. Consult the Virtualization Deployment and Administration Guide for details.
2.3.1. Benefits of Migrating Virtual Machines
- Load balancing
- When a host machine is overloaded, one or more of its virtual machines could be migrated to other hosts using live migration. Similarly, machines that are not running and tend to overload can be migrated using offline migration.
- Upgrading or making changes to the host
- When the need arises to upgrade, add, or remove hardware devices on a host, virtual machines can be safely relocated to other hosts. This means that guests do not experience any downtime due to changes that are made to hosts.
- Energy saving
- Virtual machines can be redistributed to other hosts and the unloaded host systems can be powered off to save energy and cut costs in low usage periods.
- Geographic migration
- Virtual machines can be moved to other physical locations for lower latency or for other reasons.
2.3.2. Virtualized to Virtualized Migration (V2V)
virt-v2vtool converts and imports virtual machines from Xen, other versions of KVM, and VMware ESX.
virt-p2vtool. For details, see the P2V Knowledgebase article.
- Security-Enhanced Linux, or SELinux, provides Mandatory Access Control (MAC) for all Linux systems, and thus benefits also Linux guests. Under the control of SELinux, all processes and files are given a type, and their access on the system is limited by fine-grained controls of various types. SELinux limits the abilities of an attacker and works to prevent many common security exploits such as buffer overflow attacks and privilege escalation.
- sVirt is a technology included in Red Hat Enterprise Linux 7 that integrates SELinux and virtualization. It applies Mandatory Access Control (MAC) to improve security when using virtual machines, and hardens the system against hypervisor bugs that might be used to attack the host or another virtual machine.
2.5. Disaster Recovery
Chapter 3. Introduction to Red Hat Virtualization Products and Features
3.1. KVM and Virtualization in Red Hat Enterprise Linux
virsh). Virtual machines are executed and run as multi-threaded Linux processes, controlled by these tools.
Figure 3.1. KVM architecture
- The KVM hypervisor supports overcommitting of system resources. Overcommitting means allocating more virtualized CPUs or memory than the available resources on the system, so the resources can be dynamically swapped when required by one guest and not used by another. This can improve how efficiently guests use the resources of the host, and can make it possible for the user to require fewer hosts.
ImportantOvercommitting involves possible risks to system stability. For more information on overcommitting with KVM, and the precautions that should be taken, refer to the Red Hat Enterprise Linux 7 Virtualization Deployment and Administration Guide.
- Kernel Same-page Merging (KSM), used by the KVM hypervisor, enables KVM guests to share identical memory pages. These shared pages are usually common libraries or other identical, high-use data. KSM allows for greater guest density of identical or similar guest operating systems by avoiding memory duplication.
NoteFor more information on KSM, refer to the Red Hat Enterprise Linux 7 Virtualization Tuning and Optimization Guide.
- QEMU guest agent
- The QEMU guest agent runs on the guest operating system and makes it possible for the host machine to issue commands to the guest operating system.
NoteFor more information on the QEMU guest agent, refer to the Red Hat Enterprise Linux 7 Virtualization Deployment and Administration Guide.
- Disk I/O throttling
- When several virtual machines are running simultaneously, they can interfere with the overall system performance by using excessive disk I/O. Disk I/O throttling in KVM provides the ability to set a limit on disk I/O requests sent from individual virtual machines to the host machine. This can prevent a virtual machine from over-utilizing shared resources, and impacting the performance of other virtual machines.
NoteFor instructions on using disk I/O throttling, refer to the Red Hat Enterprise Linux 7 Virtualization Tuning and Optimization Guide.
- Automatic NUMA balancing
- Automatic non-uniform memory access (NUMA) balancing moves tasks, which can be threads or processes closer to the memory they are accessing. This improves the performance of applications running on non-uniform memory access (NUMA) hardware systems, without any manual tuning required for Red Hat Enterprise Linux 7 guests.
NoteFor more information on automatic NUMA balancing, refer to the Red Hat Enterprise Linux 7 Virtualization Tuning and Optimization Guide.
- Virtual CPU hot add
- Virtual CPU (vCPU) hot add capability provides the ability to increase processing power on running virtual machines as needed, without shutting down the guests. The vCPUs assigned to a virtual machine can be added to a running guest to either meet the workload's demands, or to maintain the Service Level Agreement (SLA) associated with the workload.
NoteFor more information on virtual CPU hot add, refer to the Red Hat Enterprise Linux 7 Virtualization Deployment and Administration Guide.
- Nested virtualization
- As a Technology Preview, Red Hat Enterprise Linux 7.2 and later offers hardware-assisted nested virtualization. This feature enables KVM guests to act as hypervisors and create their own guests.This can for example be used for debugging hypervisors on a virtual machine or testing larger virtual deployments on a limited amount of physical machines.
NoteFor further information on setting up and using nested virtualization, see Red Hat Enterprise Linux 7 Virtualization Deployment and Administration Guide.
- KVM guest virtual machine compatibility
- Red Hat Enterprise Linux 7 servers have certain support limits.The following URLs explain the processor and memory amount limitations for Red Hat Enterprise Linux:
For a complete chart of supported operating systems and host and guest combinations refer to Red Hat Customer Portal
- For the host system: https://access.redhat.com/site/articles/rhel-limits
- For the KVM hypervisor: https://access.redhat.com/site/articles/rhel-kvm-limits
NoteTo verify whether your processor supports virtualization extensions and for information on enabling virtualization extensions if they are disabled, refer to the Red Hat Enterprise Linux 7 Virtualization Deployment and Administration Guide.
3.2. libvirt and libvirt Tools
- A virtualization layer to securely manage virtual machines on a host.
- An interface for managing local and networked hosts.
- The APIs required to provision, create, modify, monitor, control, migrate, and stop virtual machines. Although multiple hosts may be accessed with libvirt simultaneously, the APIs are limited to single node operations.
NoteOnly operations supported by the hypervisor can be performed using libvirt.
3.3. Virtualized Hardware Devices
- Virtualized and emulated devices
- Paravirtualized devices
- Physically shared devices
3.3.1. Virtualized and Emulated Devices
- Virtual CPUs (vCPUs)
- On Red Hat Enterprise Linux 7.2 and above, the host system can have up to 240 virtual CPUs (vCPUs) that can be presented to guests for use, regardless of the number of host CPUs. This is up from 160 in Red Hat Enterprise Linux 7.0.
- Emulated system components
- The following core system components are emulated to provide basic system functions:
- Intel i440FX host PCI bridge
- PIIX3 PCI to ISA bridge
- PS/2 mouse and keyboard
- EvTouch USB graphics tablet
- PCI UHCI USB controller and a virtualized USB hub
- Emulated serial ports
- EHCI controller, virtualized USB storage and a USB mouse
- USB 3.0 xHCI host controller (Technology Preview in Red Hat Enterprise Linux 7.3)
- Emulated storage drivers
- Storage devices and storage pools can use emulated drivers to attach storage devices to virtual machines. The guest uses an emulated storage driver to access the storage pool.Note that like all virtual devices, the storage drivers are not storage devices. The drivers are used to attach a backing storage device, file or storage pool volume to a virtual machine. The backing storage device can be any supported type of storage device, file, or storage pool volume.
- The emulated IDE driver
- KVM provides two emulated PCI IDE interfaces. An emulated IDE driver can be used to attach any combination of up to four virtualized IDE hard disks or virtualized IDE CD-ROM drives to each virtual machine. The emulated IDE driver is also used for virtualized CD-ROM and DVD-ROM drives.
- The emulated floppy disk drive driver
- The emulated floppy disk drive driver is used for creating virtualized floppy drives.
- Emulated sound devices
- An emulated (Intel) HDA sound device,
intel-hda, is supported in the following guest operating systems:
- Red Hat Enterprise Linux 7, for the AMD64 and Intel 64 architecture
- Red Hat Enterprise Linux 4, 5, and 6, for the 32-bit AMD and Intel architecture and the AMD64 and Intel 64 architecture
NoteThe following emulated sound device is also available, but is not recommended due to compatibility issues with certain guest operating systems:
ac97, an emulated Intel 82801AA AC97 Audio compatible sound card
- Emulated graphics cards
- The following emulated graphics cards are provided.
Guests can connect to these devices with the Simple Protocol for Independent Computing Environments (SPICE) protocol or with the Virtual Network Computing (VNC) system.
- A Cirrus CLGD 5446 PCI VGA card
- A standard VGA graphics card with Bochs VESA extensions (hardware level, including all non-standard modes)
- Emulated network devices
- The following two emulated network devices are provided:
e1000device emulates an Intel E1000 network adapter (Intel 82540EM, 82573L, 82544GC).
rtl8139device emulates a Realtek 8139 network adapter.
- Emulated watchdog devices
- A watchdog can be used to automatically reboot a virtual machine when the machine becomes overloaded or unresponsive.Red Hat Enterprise Linux 7 provides the following emulated watchdog devices:
Both watchdog devices are supported in i386 and x86_64 architectures for guest operating systems Red Hat Enterprise Linux 6.2 and above.
i6300esb, an emulated Intel 6300 ESB PCI watchdog device. It is supported in guest operating system Red Hat Enterprise Linux versions 6.0 and above, and is the recommended device to use.
ib700, an emulated iBase 700 ISA watchdog device. The
ib700watchdog device is only supported in guests using Red Hat Enterprise Linux 6.2 and above.
3.3.2. Paravirtualized Devices
- The paravirtualized network device (virtio-net)
- The paravirtualized network device is a virtual network device that provides network access to virtual machines with increased I/O performance and lower latency.
- The paravirtualized block device (virtio-blk)
- The paravirtualized block device is a high-performance virtual storage device that provides storage to virtual machines with increased I/O performance and lower latency. The paravirtualized block device is supported by the hypervisor and is attached to the virtual machine (except for floppy disk drives, which must be emulated).
- The paravirtualized controller device (virtio-scsi)
- The paravirtualized SCSI controller device provides a more flexible and scalable alternative to virtio-blk. A virtio-scsi guest is capable of inheriting the feature set of the target device, and can handle hundreds of devices compared to virtio-blk, which can only handle 28 devices.virtio-scsi is fully supported for the following guest operating systems:
- Red Hat Enterprise Linux 7
- Red Hat Enterprise Linux 6.4 and above
- The paravirtualized clock
- Guests using the Time Stamp Counter (TSC) as a clock source may suffer timing issues. KVM works around hosts that do not have a constant Time Stamp Counter by providing guests with a paravirtualized clock. Additionally, the paravirtualized clock assists with time adjustments needed after a guest runs the sleep (S3) or suspend to RAM operations.
- The paravirtualized serial device (virtio-serial)
- The paravirtualized serial device is a bytestream-oriented, character stream device, and provides a simple communication interface between the host's user space and the guest's user space.
- The balloon device (virtio-balloon)
- The balloon device can designate part of a virtual machine's RAM as not being used (a process known as inflating the balloon), so that the memory can be freed for the host (or for other virtual machines on that host) to use. When the virtual machine needs the memory again, the balloon can be deflated and the host can distribute the RAM back to the virtual machine.
- The paravirtualized random number generator (virtio-rng)
- The paravirtualized random number generator enables virtual machines to collect entropy, or randomness, directly from the host to use for encrypted data and security. Virtual machines can often be starved of entropy because typical inputs (such as hardware usage) are unavailable. Sourcing entropy can be time-consuming. virtio-rng makes this process faster by injecting entropy directly into guest virtual machines from the host.
- The paravirtualized graphics card (QXL)
- The paravirtualized graphics card works with the QXL driver to provide an efficient way to display a virtual machine's graphics from a remote host. The QXL driver is required to use SPICE.
3.3.3. Physical Host Devices
- VFIO device assignment
- Virtual Function I/O (VFIO) is a new kernel driver in Red Hat Enterprise Linux 7 that provides virtual machines with high performance access to physical hardware.VFIO attaches PCI devices on the host system directly to virtual machines, providing guests with exclusive access to PCI devices for a range of tasks. This enables PCI devices to appear and behave as if they were physically attached to the guest virtual machine.VFIO improves on previous PCI device assignment architecture by moving device assignment out of the KVM hypervisor, and enforcing device isolation at the kernel level. VFIO offers better security and is compatible with secure boot. It is the default device assignment mechanism in Red Hat Enterprise Linux 7.VFIO increases the number of assigned devices to 32 in Red Hat Enterprise Linux 7, up from a maximum 8 devices in Red Hat Enterprise Linux 6. VFIO also supports assignment of NVIDIA GPUs.
NoteFor more information on VFIO device assignment, refer to the Red Hat Enterprise Linux 7 Virtualization Deployment and Administration Guide.
- USB, PCI, and SCSI passthrough
- The KVM hypervisor supports attaching USB, PCI, and SCSI devices on the host system to virtual machines. USB, PCI, and SCSI device assignment makes it possible for the devices to appear and behave as if they were physically attached to the virtual machine. Thus, it provides guests with exclusive access to these devices for a variety of tasks.
NoteFor more information on USB, PCI, and SCSI passthrough, refer to the Red Hat Enterprise Linux 7 Virtualization Deployment and Administration Guide.
- SR-IOV (Single Root I/O Virtualization) is a PCI Express (PCI-e) standard that extends a single physical PCI function to share its PCI resources as separate, virtual functions (VFs). Each function is capable of being used by a different virtual machine via PCI device assignment.An SR-IOV-capable PCI-e device provides a Single Root function (for example, a single Ethernet port) and presents multiple, separate virtual devices as unique PCI device functions. Each virtual device may have its own unique PCI configuration space, memory-mapped registers, and individual MSI-based interrupts.
NoteFor more information on SR-IOV, refer to the Red Hat Enterprise Linux 7 Virtualization Deployment and Administration Guide.
- N_Port ID Virtualization (NPIV) is a functionality available with some Fibre Channel devices. NPIV shares a single physical N_Port as multiple N_Port IDs. NPIV provides similar functionality for Fibre Channel Host Bus Adapters (HBAs) that SR-IOV provides for PCIe interfaces. With NPIV, virtual machines can be provided with a virtual Fibre Channel initiator to Storage Area Networks (SANs).NPIV can provide high density virtualized environments with enterprise-level storage solutions.
NoteFor more information on NPIV, refer to the Red Hat Enterprise Linux 7 Virtualization Deployment and Administration Guide.
3.3.4. Guest CPU Models
3.4.1. Storage Pools
- Local storage pools
- Local storage pools are attached directly to the host server. They include local directories, directly attached disks, physical partitions, and Logical Volume Management (LVM) volume groups on local devices. Local storage pools are useful for development, testing and small deployments that do not require migration or large numbers of virtual machines. Local storage pools may not be suitable for many production environment, because they do not support live migration.
- Networked (shared) storage pools
- Networked storage pools include storage devices shared over a network using standard protocols. Networked storage is required when migrating virtual machines between hosts with virt-manager, but is optional when migrating with
virsh. Networked storage pools are managed by libvirt.
3.4.2. Storage Volumes
3.4.3. Emulated Storage Devices
- virtio-scsi is the recommended paravirtualized device for guests using large numbers of disks or advanced storage features such as TRIM. Guest driver installation may be necessary on guests using operating systems other than Red Hat Enterprise Linux 7.
- virtio-blk is a paravirtualized storage device suitable for exposing image files to guests. virtio-blk can provide the best disk I/O performance for virtual machines, but has fewer features than virtio-scsi.
- IDE is recommended for legacy guests that do not support virtio drivers. IDE performance is lower than virtio-scsi or virtio-blk, but it is widely compatible with different systems.
- ATAPI CD-ROMs and virtio-scsi CD-ROMs are available and make it possible for guests to use ISO files or the host's CD-ROM drive. virtio-scsi CD-ROMs can be used with guests that have the virtio-scsi driver installed. ATAPI CD-ROMs offer wider compatibility but lower performance.
- USB mass storage devices and floppy disks
- Emulated USB mass storage devices and floppy disks are available when removable media are required. USB mass storage devices are preferable to floppy disks due to their larger capacity.
3.4.4. Host Storage
- Image files
- Image files can only be stored on a host file system. The image files can be stored on a local file system, such as ext4 or xfs, or a network file system, such as NFS.Tools such as libguestfs can manage, back up, and monitor files. Disk image formats on KVM include:
- Raw image files contain the contents of the disk with no additional metadata.Raw files can either be pre-allocated or sparse, if the host file system allows it. Sparse files allocate host disk space on demand, and are therefore a form of thin provisioning. Pre-allocated files are fully provisioned but have higher performance than sparse files.Raw files are desirable when disk I/O performance is critical and transferring the image file over a network is rarely necessary.
- qcow2 image files offer a number of advanced disk image features, including backing files, snapshots, compression, and encryption. They can be used to instantiate virtual machines from template images.qcow2 files are typically more efficient to transfer over a network, because only sectors written by the virtual machine are allocated in the image.Red Hat Enterprise Linux 7 supports the qcow2 version 3 image file format.
- LVM volumes
- Logical volumes (LVs) can be used for disk images and managed using the system's LVM tools. LVM offers higher performance than file systems because of its simpler block storage model.LVM thin provisioning offers snapshots and efficient space usage for LVM volumes, and can be used as an alternative to migrating to qcow2.
- Host devices
- Host devices such as physical CD-ROMs, raw disks, and logical unit numbers (LUNs) can be presented to the guest. This enables SAN or iSCSI LUNs as well as local CD-ROM media to be used by the guest with good performance.Host devices can be used when storage management is done on a SAN instead of on hosts.
- Distributed storage systems
- Gluster volumes can be used as disk images. This enables high-performance clustered storage over the network.Red Hat Enterprise Linux 7 includes native support for disk images on GlusterFS. This enables a KVM host to boot virtual machine images from GlusterFS volumes, and to use images from a GlusterFS volume as data disks for virtual machines. When compared to GlusterFS FUSE, the native support in KVM delivers higher performance.
3.5. Virtual Networking
libvirt's virtual network configuration. The host therefore acts as a virtual network switch, which can be configured in a number of different ways to fit the guest's networking needs.
default. Guests on this network can make the following connections:
- With each other and with the virtualization host
- Both inbound and outbound traffic is possible, but is affected by the firewalls in the guest operating system's network stack and by libvirt network filtering rules attached to the guest interface.
- With other hosts on the network beyond the virtualization host
- Only outbound traffic is possible, and is affected by Network Address Translation (NAT) rules, as well as the host system's firewall.
- Isolated mode
- The guests are connected to a network that does not allow any traffic beyond the virtualization host.
- Routed mode
- The guests are connected to a network that routes traffic between the guest and external hosts without performing any NAT. This enables incoming connections but requires extra routing-table entries for systems on the external network.
- Bridged mode
- The guests are connected to a bridge device that is also connected directly to a physical ethernet device connected to the local ethernet. This makes the guest directly visible on the physical network, and thus enables incoming connections, but does not require any extra routing-table entries.
defaultnetwork is installed along with the libvirt package, and automatically started when the
libvirtdservice is started. If more advanced functionality is needed, additional networks can be created and configured using either virsh or virt-manager, and the guest XML configuration file can be edited to use one of these new networks.
Chapter 4. Quick Start Tutorial on Virtualization in Red Hat Enterprise Linux 7
4.1. Tutorial overview
4.2. Basic Requirements and Setup
- Virtualization with the KVM hypervisor is currently only supported on Intel64 and AMD 64 systems.
- Disk space and RAM
- 6 GB free disk space
- 2 GB RAM
- Customer Portal registration
- To install virtualization packages, your host machine must be registered and subscribed to the Red Hat Customer Portal. To register run the
subscription-manager registercommand and follow the prompts. Alternatively, run the Red Hat Subscription Manager application from → on the desktop to register.
- Required packages
- Before you can use virtualization, a basic set of virtualization packages must be installed on your computer.
Procedure 4.1. Installing the virtualization packages with
yumTo use virtualization on Red Hat Enterprise Linux, the
libvirtpackages must be installed. These provide the user-level KVM emulator, disk image manager, and virtualization management tools on the host system.
- Install the qemu-kvm, qemu-img, libvirt, and virt-manager packages:
# yum install qemu-kvm qemu-img libvirt virt-manager
- Download a binary DVD ISO image from the Red Hat Customer Portal. This example uses Red Hat Enterprise Linux 6 Workstation. The image file will be used to install the guest virtual machine's operating system.
NoteIf you encounter any problems during the installation process, see the Troubleshooting section of the Red Hat Enterprise Linux 7 Virtualization Deployment and Administration Guide.
4.3. Creating a Virtual Machine with Virtual Machine Manager
4.3.1. Introduction to Virtual Machine Manager
virt-manager→ press Enter.
Figure 4.1. The Virtual Machine Manager interface
- Create new virtual machine: Click to create a new virtual machine.
- Virtual machines: A list of configured connections and all guest virtual machines associated with them. When a virtual machine is created, it is listed here. When a guest is running, an animated graph shows the guest's CPU usage in the CPU usage column.After selecting a virtual machine from this list, use the following buttons to control the selected virtual machine's state:
- Open: Opens the guest virtual machine console and details in a new window.
- Run: Turns on the virtual machine.
- Pause: Pauses the virtual machine.
- Shut down: Shuts down the virtual machine. Clicking the arrow displays a drop-down menu with several options for turning off the virtual machine, including Reboot, Shut Down, Force Reset, Force Off, and Save.
- Clone: Clones the virtual machine.
- Migrate: Migrates the virtual machine to another host.
- Delete: Deletes the virtual machine.
4.3.2. Creating a Virtual Machine with Virtual Machine Manager
Procedure 4.2. Creating a guest virtual machine with Virtual Machine Manager
Open Virtual Machine ManagerClick→ →orPress the Super key, type
virt-manager, and press Enter
Create a new virtual machineClick to open the wizard.
Specify the installation methodStart the creation process by choosing the method of installing the new virtual machine.
Figure 4.2. Select the installation methodFor this tutorial, select Local install media (ISO image). This installation method uses an image of an installation disk (in this case an
.isofile). Click to continue to the next step.
Locate installation media
- Select the
Use ISO Imageoption.
- Click→ buttons.
- Locate the ISO downloaded in Procedure 4.1, “Installing the virtualization packages with
yum” on your machine.
- Select the ISO file and click.
- Ensure that Virtual Machine Manager correctly detected the OS type. If not, uncheck
Automatically detect operating system based on install mediaand select Linux from the drop-down and Red Hat Enterprise Linux 6 from the drop-down.
Figure 4.3. Local ISO image installation
Configure memory and CPUYou can use step 3 of the wizard to configure the amount of memory and the number of CPUs to allocate to the virtual machine. The wizard shows the number of CPUs and amount of memory available to allocate.For this tutorial, leave the default settings and click.
Figure 4.4. Configuring CPU and Memory
Configure storageUsing step 4 of the wizard, you can assign storage to the guest virtual machine. The wizard shows options for storage, including where to store the virtual machine on the host machine. For this tutorial, leave the default settings and click.
Figure 4.5. Configuring storage
Name and reviewUsing step 5 of the wizard, you can create a name for the virtual machine and configure network settings. For this tutorial, enter a name for the virtual machine, verify the settings, and click Virtual Machine Manager will create a virtual machine with the specified hardware settings..
Figure 4.6. Naming and verification
4.3.3. Exploring the Guest Virtual Machine
Figure 4.7. The guest virtual machine console
- Show the graphical console: Shows the virtual machine's display. The virtual machine can be operated from the console the same as a physical machine.
- Show virtual hardware details: Shows details about the virtual hardware that the guest is using. These include an overview of basic system details, performance, processor, memory, and boot settings, and details of the system's virtual devices. For more information, refer to the Virtualization Deployment and Administration Guide.
- Run: Turns on the virtual machine.
- Pause: Pauses the virtual machine.
- Shut down: Shuts down the virtual machine. Clicking the arrow displays a drop-down menu with several options for turning off the virtual machine, including Reboot, Shut Down, Force Reset, Force Off, and Save.
- Manage snapshots: Enables creating, running, and managing snapshots of the virtual machine. For details, see the Virtualization Deployment and Administration Guide.
- Send Key: Sends key combinations such as Ctrl+Alt+Backspace, Ctrl+Alt+Delete, Ctrl+Alt+F1, PrintScreen, and more to the virtual machine.
- Full screen: Switches the virtual machine to full screen view.
Chapter 5. Virtualization Tools
virshcommand as well, but in read-only mode.
virshis installed as part of the libvirt-client package.
virsh, refer to the Red Hat Enterprise Linux 7 Virtualization Deployment and Administration Guide.
virsh. It enables the user to use a GUI for performing actions equivalent to a number of
virt-commands, such as controlling the life cycle of existing machines, provisioning new machines, managing virtual networks, accessing the graphical console of virtual machines, and viewing performance statistics. For a demonstration of using
virt-manager, see Section 4.3, “Creating a Virtual Machine with Virtual Machine Manager”. This tool is provided by the virt-manager package.
virt-manager, refer to the Red Hat Enterprise Linux 7 Virtualization Deployment and Administration Guide.
virt-install, refer to the Red Hat Enterprise Linux 7 Virtualization Deployment and Administration Guide.
guestfishtool uses the libguestfs library and exposes all functionality provided by the
guestfishon running virtual machines may cause corruption of the disk image. Use the
guestfishcommand with the
--ro(read-only) option if the disk image is being used by a running virtual machine.
guestfish, refer to the Red Hat Enterprise Linux 7 Virtualization Deployment and Administration Guide.
5.5. GNOME Boxes
virt-manager, but offers fewer guest management options. Boxes provides a way to test different operating systems and applications from the desktop with minimal configuration. Virtual systems can be installed manually or with the express installation function, which automatically pre-configures virtual machines with optimal settings. This tool is provided by the gnome-boxes package.
5.6. Other Useful Tools
- A command-line utility used to mount virtual machine file systems and disk images on the host machine. To unmount content mounted this way, use
guestunmountBoth tools are installed as part of the libguestfs-tools-c package.
--rw(read/write) mode to access a disk that is currently being used by a guest may cause the disk to become corrupted. Do not use
--rw(read/write) mode on live virtual machines. Use the
guestmountcommand with the
--ro(read-only) option if the disk image is being used.
- A command-line utility for quickly building and customizing new virtual machines. This tool is installed in Red Hat Enterprise Linux 7.1 and later as part of the libguestfs-tools package.
- A command-line utility that can be used to quickly view the contents of one or more files in a specified virtual machine's disk or disk image. This tool is installed as part of the libguestfs-tools package.
- A command-line utilitys used for copying files or directories from the host to a guest, and from a guest to the host, respectively. These tools are installed as part of the libguestfs-tools package.
virt-copy-inonly on turned off virtual machines that are not being used by another disk-editing tool. Using
virt-copy-inon an active guest image or an image that is being edited may cause disk corruption in the virtual machine.
- A command-line utility for customizing virtual machine disk images. virt-customize can be used to install packages, edit configuration files, run scripts, and set passwords. This tool is installed in Red Hat Enterprise Linux 7.1 and later as part of the libguestfs-tools package.
- A command-line utility used to show the actual physical disk usage of virtual machines, similar to the command-line utility
df. Note that this tool does not work across remote connections. It is installed as part of the libguestfs-tools package.
- A command-line utility for showing differences between the file systems of two virtual machines. This can be useful for example to discover which files have changed between snapshots. This tool is installed in Red Hat Enterprise Linux 7.1 and later as part of the libguestfs-tools package.
- A command-line utility used to edit files that exist on a specified virtual machine. This tool is installed as part of the libguestfs-tools package.
virt-editon live virtual machines may cause disk corruption in the virtual machine. Although the
virt-editcommand will try to prevent users from editing files on live virtual machines, it is not guaranteed to catch all instances. Do not use
virt-editon a live virtual machine.
- A command-line utility used to discover file systems, partitions, logical volumes and their sizes in a disk image or virtual machine. One common use is in shell scripts, to iterate over all file systems in a disk image. This tool is installed as part of the libguestfs-tools package.
NoteThis tool replaces
- A command-line utility capable of formatting guest image files, but also logical volumes on the host machine. This tool is installed as part of the libguestfs-tools package.
virt-formatonly on turned off virtual machines that are not being used by another disk-editing tool. Using
virt-formaton an active guest image or an image that is being edited may cause disk corruption in the virtual machine.
- A command-line utility that can examine a virtual machine or disk image to determine the version of its operating system and other information. It can also produce XML output, which can be piped into other programs. Note that
virt-inspectorcan only inspect one virtual machine at a time. This tool is installed as part of the libguestfs-tools package.
- A command-line utility for listing log files from virtual machines. This tool is installed in Red Hat Enterprise Linux 7.1 and later as part of the libguestfs-tools package.
- A command-line utility that lists files and directories inside a virtual machine. This tool is installed as part of the libguestfs-tools package.
- A command-line utility for creating a file system based on a tar archive or files in a directory. It is similar to tools like
mksquashfs, but it can create common file system types such as ext2, ext3 and NTFS, and the size of the file system created can be equal to or greater than the size of the files it is based on. This tool is provided as part of the libguestfs-tools package.
- A bootable tool that, when used in combination with virt-v2v, makes it possible to convert physical machines into KVM virtual machines. Note that virt-p2v is only supported in Red Hat Enterprise Linux 7.3 and later.
- A command-line utility that provides a rescue shell and some simple recovery tools for unbootable virtual machines and disk images. It can be run on any virtual machine known to libvirt, or directly on disk images. This tool is installed as part of the libguestfs-tools package.
virt-rescueon running virtual machines may cause disk corruption in the virtual machine.
virt-rescueattempts to prevent its own use on running virtual machines, but cannot catch all cases. Using the command with the
--ro(read-only) option will not cause disk corruption, but may give strange or inconsistent results.Avoid using
virt-rescueon a running virtual machine.
- A command-line utility to resize virtual machine disks, and resize or delete any partitions on a virtual machine disk. It works by copying the guest image and leaving the original disk image untouched. This tool is installed as part of the libguestfs-tools package.
virt-resizeon running virtual machines can give inconsistent results. It is recommended to shut down virtual machines before attempting to resize them.
- A command-line utility to make a virtual machine disk (or any disk image) thin-provisioned. The tool can convert free space in the disk image to free space on the host.
- A command-line utility to reset, customize, or unconfigure virtual machines to prepare a template for creating clones. This tool is installed as part of the libguestfs-tools package.
ImportantVirtual machines must be shut down before running
virt-sysprep. To preserve a virtual machine's existing contents, snapshot, copy or clone the disk before running
- Command-line archive tools for packing a virtual machine disk image directory into a tarball, and unpacking an uncompressed tarball into a virtual machine disk image or specified libvirt guest, respectively. These tools are installed as part of the libguestfs-tools package.
virt-tar-incommand on a live virtual machine may cause disk corruption in the virtual machine. The virtual machine must be shut down before using this command.
- A command-line utility similar to
top, which shows statistics related to guest virtual machines. This tool is contained the virt-top package. See
man virt-topfor details.
- A command-line utility for converting virtual machines from a foreign hypervisor to run on KVM managed by libvirt. Currently, virt-v2v can convert Red Hat Enterprise Linux and Windows guests running on Xen and VMware ESX. The virt-v2v tool is installed in Red Hat Enterprise Linux 7.1 and later as part of the virt-v2v package.
- A lightweight utility for displaying the graphical console of a virtual machine via the VNC and SPICE protocols. This tool is provided by the virt-viewer package.
- A shell script that detects whether a program is running in a virtual machine. This tool is provided by the virt-what package.
- The virt-who package is a Red Hat Enterprise Linux host agent that queries libvirt for guest UUIDs. It then passes that data to the local entitlement server for the purposes of issuing certificates. This tool is provided by the virt-who package.
- A command-line utility to validate libvirt XML files for compliance with the published schema. This tool is installed as part of the libvirt-client package. See
man virt-xml-validatefor details.
Appendix A. Revision History
|Revision 1.0-51||Thu Aug 03 2017|
|Revision 1.0-46||Mon Oct 17 2016|
|Revision 1.0-44||Mon Dec 21 2015|
|Revision 1.0-43||Thu Oct 08 2015|
|Revision 1.0-42||Sun Jun 28 2015|