The VM Guest listing shows all VM Guests managed by libvirt on a VM Host Server.

Opening a Graphical Console to a VM Guest lets you interact with the machine like a physical host via a VNC connection. If accessing the VNC server requires authentication, you are prompted to enter a user name (if applicable) and a password.

Once you click into the VNC console, the cursor is “grabbed” and cannot be used outside the console anymore. To release it, press Alt–Ctrl.

Tip: Seamless (Absolute) Cursor Movement

In order to prevent the console from grabbing the cursor and to enable seamless cursor movement, add a tablet input device to the VM Guest. See Section 13.1, “Enabling Seamless and Synchronized Cursor Movement” for more information.

Certain key combinations such as Ctrl–Alt–Del are interpreted by the host system and are not passed to the VM Guest. To pass such key combinations to a VM Guest, open the Send Key menu from the VNC window and choose the desired key combination entry. The Send Key menu is only available when using Virtual Machine Manager and virt-viewer. With Virtual Machine Manager you can alternatively use the “sticky key” feature as explained in Tip: Passing Key Combinations to Virtual Machines.

Note: Supported VNC Viewer

Principally all VNC viewers are able to connect to the console of a VM Guest. However, if you are using SASL authentication and/or TLS/SSL connection to access the guest, the options become limited. Common VNC viewers such as tigervnc support neither SASL authentication nor TSL/SSL. The only supported alternative to Virtual Machine Manager and virt-viewer is vinagre.

10.2.2 Opening a Graphical Console with virt-viewer #

virt-viewer is a simple VNC viewer with added functionality for displaying VM Guest consoles. It can, for example, be started in “wait” mode, where it waits for a VM Guest to start before it connects. It also supports automatically reconnecting to a VM Guest that is rebooted.

virt-viewer addresses VM Guests by name, by ID or by UUID. Use virsh list --all to get this data.

To connect to a guest that is running or paused, use either the ID, UUID, or name. VM Guests that are shut off do not have an ID—you can only connect by UUID or name.

Connect to guest with the ID 8

virt-viewer 8

Connect to the inactive guest named sles12; the connection window will open once the guest starts

virt-viewer --wait sles12

With the --wait option, the connection will be upheld even if the VM Guest is not running at the moment. Once the guest starts, the viewer will be launched.

For more information, see virt-viewer --help or man 1 virt-viewer.

Note: Password Input on Remote connections with SSH

When using virt-viewer to open a connection to a remote host via SSH, the SSH password needs to be entered twice. The first time for authenticating with libvirt, the second time for authenticating with the VNC server. The second password needs to be provided on the command line where virt-viewer was started.

Starting, stopping or pausing a VM Guest can be done with either Virtual Machine Manager or virsh. You can also configure a VM Guest to be automatically started when booting the VM Host Server.

When shutting down a VM Guest, you may either shut it down gracefully, or force the shutdown. The latter is equivalent to pulling the power plug on a physical host and is only recommended if there are no alternatives. Forcing a shutdown may cause file system corruption and loss of data on the VM Guest.

Tip: Graceful Shutdown

In order to be able to perform a graceful shutdown, the VM Guest must be configured to support ACPI. If you have created the guest with vm-install or with Virtual Machine Manager, ACPI should be available. Use the following procedure in Virtual Machine Manager to check:

Double-click the VM Guest entry in Virtual Machine Manager. Choose View › Details and then Overview › Machine Settings. ACPI should be checked.

Depending on the guest operating system, enabling ACPI may not be sufficient. It is strongly recommended to test shutting down and rebooting a guest before releasing it to production. openSUSE or SUSE Linux Enterprise Desktop, for example, may require PolKit authorization for shutdown and reboot. Make sure this policy is turned off on all VM Guests.

If ACPI was enabled during a Windows XP/Server 2003 guest installation, turning it on in the VM Guest configuration alone is not sufficient. See the following articles for more information:

http://support.microsoft.com/kb/314088/EN-US/

http://support.microsoft.com/?kbid=309283

A graceful shutdown is of course always possible from within the guest operating system, regardless of the VM Guest's configuration.

Saving a VM Guest preserves the exact state of the guest’s memory. The operation is slightly similar to hibernating a computer. A saved VM Guest can be quickly restored to its previously saved running condition.

When saved, the VM Guest is paused, its current memory state is saved to disk, and then the guest is stopped. The operation does not make a copy of any portion of the VM Guest’s virtual disk. The amount of time taken to save the virtual machine depends on the amount of memory allocated. When saved, a VM Guest’s memory is returned to the pool of memory available on the VM Host Server.

The restore operation loads a VM Guest’s previously saved memory state file and starts it. The guest is not booted but rather resumes at the point where it was previously saved. The operation is slightly similar to coming out of hibernation.

The VM Guest is saved to a state file. Make sure there is enough space on the partition you are going to save to. Issue the following command on the guest to get a rough estimation of the file size in megabytes to be expected:

free -m | awk '/^Mem:/ {print $3}'

Warning

After using the save operation, do not boot or start the saved VM Guest. Doing so would cause the machine's virtual disk and the saved memory state to get out of sync and can result in critical errors when restoring the guest. The only "proper" way to use a saved VM Guest is using the restore operation.

virsh restore /virtual/saves/opensuse13.vmsave

VM Guest snapshots are snapshots of the complete virtual machine including the state of CPU, RAM, and the content of all writable disks. To use virtual machine snapshots, you must have at least one non-removable and writable block device using the qcow2 disk image format.

Note

Snapshots are supported on KVM VM Host Servers only.

Snapshots let you restore the state of the machine at a particular point in time. This is for example useful to undo a faulty configuration or the installation of a lot of packages. It's also helpful for testing purposes, since it allows you to go back to a defined state at any time.

Snapshots can be taken either from running guests or from a guest currently not running. Taking a screenshot from a guest that is shut down ensures data integrity. In case you want to create a snapshot from a running system, be aware of the fact that the snapshot only captures the state of the disk(s), not the state of the memory. Therefore you need to ensure that:

Starting a snapshot reverts the machine back to the state it was in when the snapshot was taken. Any changes written to the disk after that point in time will get lost when starting the snapshot. Also note that starting a snapshot will restore the state (shut off or running) the machine was in when having taken the snapshot. If starting a snapshot of the state Shutoff, you will have to start the VM Guest afterwards.

10.5.1 Creating and Managing Snapshots with Virtual Machine Manager #

To open the snapshot management view in Virtual Machine Manager, open the VNC window as described in Section 10.2.1, “Opening a Graphical Console with Virtual Machine Manager”. Now either choose View › Snapshots or click the snapshot icon in the toolbar.

The list of existing snapshots for the chosen VM Guest is displayed in the left-hand part of the window. The snapshot that was last started is marked with a green tick. The right-hand part of the window shows details of the snapshot currently marked in the list. These details include the snapshot's title and time stamp, the state of the VM Guest at the time the snapshot was taken and a description. Snapshots from running guests also include a screenshot. The Description can be changed or added directly in this view; the other snapshot data cannot be changed.

10.5.1.1 Creating a Snapshot #

To take a new snapshot of a VM Guest, proceed as follows:

1. Shut down the VM Guest in case you want to create a snapshot from a guest that is not running.

2. Click the plus symbol in the bottom left corner of the VNC window to open the Create Snapshot window.

3. Provide a Name and, optionally, a description. The name cannot be changed once the snapshot has been taken. It is recommended to use a “speaking name”, since it makes it easier to identify the snapshot.

4. Once all data is entered, choose Finish.

10.5.1.2 Deleting a Snapshot #

To delete a snapshot of a VM Guest proceed as follows:

1. Click the symbol with the red circle in the bottom left corner of the VNC window.

2. Confirm the deletion with Yes.

10.5.1.3 Starting a Snapshot #

To start a snapshot, proceed as follows:

1. Click the “play” symbol in the bottom left corner of the VNC window.

2. Confirm the start with Yes.

tux > virsh snapshot-list
 Name                 Creation Time             State
------------------------------------------------------------
 Basic installation incl. SMT finished 2013-09-18 09:45:29 +0200 shutoff
 Basic installation incl. SMT for CLOUD3 2013-12-11 15:11:05 +0100 shutoff
 Basic installation incl. SMT for CLOUD3-HA 2014-03-24 13:44:03 +0100 shutoff
 Basic installation incl. SMT for CLOUD4 2014-07-07 11:27:47 +0200 shutoff
 Beta1 Running        2013-07-12 12:27:28 +0200 shutoff
 Beta2 prepared       2013-07-12 17:00:44 +0200 shutoff
 Beta2 running        2013-07-29 12:14:11 +0200 shutoff
 Beta3 admin node deployed 2013-07-30 16:50:40 +0200 shutoff
 Beta3 prepared       2013-07-30 17:07:35 +0200 shutoff
 Beta3 running        2013-09-02 16:13:25 +0200 shutoff
 Cloud2 GM running    2013-12-10 15:44:58 +0100 shutoff
 CLOUD3 RC prepared   2013-12-20 15:30:19 +0100 shutoff
 CLOUD3-HA Build 680 prepared 2014-03-24 14:20:37 +0100 shutoff
 CLOUD3-HA Build 796 installed (zypper up) 2014-04-14 16:45:18 +0200 shutoff
 GMC2 post Cloud install 2013-09-18 10:53:03 +0200 shutoff
 GMC2 pre Cloud install 2013-09-18 10:31:17 +0200 shutoff
 GMC2 prepared (incl. Add-On Installation) 2013-09-17 16:22:37 +0200 shutoff
 GMC_pre prepared     2013-09-03 13:30:38 +0200 shutoff
 OS + SMT + eth[01]   2013-06-14 16:17:24 +0200 shutoff
 OS + SMT + Mirror + eth[01] 2013-07-30 15:50:16 +0200 shutoff

tux > virsh snapshot-current --name admin_server
Basic installation incl. SMT for CLOUD4

tux > virsh snapshot-info sles "Basic installation incl. SMT for CLOUD4"
Name:           Basic installation incl. SMT for CLOUD4
Domain:         admin_server
Current:        yes
State:          shutoff
Location:       internal
Parent:         Basic installation incl. SMT for CLOUD3-HA
Children:       0
Descendants:    0
Metadata:       yes

virsh snapshot-screate-as --domain admin_server1 --name "Snapshot 1"2 \
--description "First snapshot"3

virsh snapshot-screate-as --domain admin_server --name "Snapshot 2" \
 --description "First live snapshot" --live

virsh snapshot-delete --domain admin_server --snapshotname "Snapshot 2"

virsh snapshot-revert --domain admin_server --snapshotname "Snapshot 1"

virsh snapshot-revert --domain admin_server --current

Deleting a VM Guest removes its XML configuration by default. Since the attached storage is not deleted by default, you will be able to use it with another VM Guest. With Virtual Machine Manager you may also delete a guest's storage files as well—this will completely erase the guest.

In order to delete a VM Guest, it has to be shut down first (refer to Section 10.3, “Changing a VM Guest's State: Start, Stop, Pause” for instructions). It is not possible to delete a running guest.

virsh undefine sles12