Objective
The following instruction will explain how to clone KVM-based Virtual Machines on Redhat Linux from command line using virt-clone command.
Operating System and Software Versions
- Operating System: – Redhat 7.3
- Software: – libvirtd (libvirt) 2.0.0
Requirements
Privileged access to your Redhat Linux installation will be required.
Difficulty
EASY
Conventions
- # – requires given linux commands to be executed with root privileges either directly as a root user or by use of
sudocommand - $ – requires given linux commands to be executed as a regular non-privileged user
Instructions
Obtain Source Virtual Machine’s information
Before we begin cloning any virtual machine we first need to obtain some basic information about it. The absolute minimum information required about the source virtual machine we are about to clone would be its name and number of disk in use. To get virtual machines name run:
# virsh list Id Name State ---------------------------------------------------- 1 server1.linuxconfig.org running
Next, we may would like to know the number of disk our source virtual machines is using as well as its location. The information about disks location is optional as it only provides us with a hint on where to store new clone disk files for the sake of consistency:
# virsh dumpxml server1.linuxconfig.org | grep "source file"
<source file='/var/lib/libvirt/images/server1.linuxconfig.org.qcow2'/>
<source file='/var/lib/libvirt/images/server1.linuxconfig.org-1.qcow2'/>
<source file='/var/lib/libvirt/images/server1.linuxconfig.org-2.qcow2'/>
From the above output we can see that our original virtual machine has three disks stored in location /var/lib/libvirt/images/.
Suspend Source Virtual Machine
Before cloning can take place our source virtual machine needs to pause/suspended:
# virsh suspend server1.linuxconfig.org Domain server1.linuxconfig.org suspended
Auto-Clone Virtual Machine
One way of cloning KVM-based Virtual Machines on Redhat Linux is to use --auto-clone switch. The main advantage of --auto-clone switch is that it automatically clones any number of source disks hence the user does not necessary need to know the location and number of the disk attached to the original virtual machine.
The disadvantage is that the user is unable to specify disk names and pride an alternative location to new cloned virtual disks. The following linux command will clone original virtual machine server1.linuxconfig.org to new clone virtual machine server2.linuxconfig.org automatically using --auto-clone switch.
# virt-clone --original=server1.linuxconfig.org --name=server2.linuxconfig.org --auto-clone WARNING Setting the graphics device port to autoport, in order to avoid conflicting. Allocating 'server2.linuxconfig.org.qcow2' | 10 GB 00:00:00 Allocating 'server1.linuxconfig.org-1-clone.qcow2' | 5.0 GB 00:00:07 Allocating 'server1.linuxconfig.org-2-clone.qcow2' | 5.0 GB 00:00:00 Clone 'server2.linuxconfig.org' created successfully.
As we can see from the above output the --auto-clone automatically cloned all virtual disks attached to the original virtual machine and appended clone keyword to any additional disks. New cloned virtual machine should be now waiting in shut off state to be started:
# virsh list --all Id Name State ---------------------------------------------------- 1 server1.linuxconfig.org paused - server2.linuxconfig.org shut off
Clone Manually Multiple Disk
To gain more control over the new cloned disk location and name we can omit the --auto-clone switch and supply all new cloned disk name and destination path using --file switch. Note the number of --file arguments supplied must be equal to the number of disks attached to the original virtual machine. Example:
# virt-clone --original=server1.linuxconfig.org --name=server2.linuxconfig.org --file /var/lib/libvirt/images/server2.linuxconfig.org.img --file /var/lib/libvirt/images/server2.linuxconfig.org-1.img --file /var/lib/libvirt/images/server2.linuxconfig.org-2.img WARNING Setting the graphics device port to autoport, in order to avoid conflicting. Allocating 'server2.linuxconfig.org.img' | 10 GB 00:00:00 Allocating 'server2.linuxconfig.org-1.img' | 5.0 GB 00:00:07 Allocating 'server2.linuxconfig.org-2.img' | 5.0 GB 00:00:00 Clone 'server2.linuxconfig.org' created successfully.
Resume/Start
At this stage we are ready to resume our original virtual machine server1.linuxconfig.org:
# virsh resume server1.linuxconfig.org Domain server1.linuxconfig.org resumed
and also start the newly cloned virtual machine server2.linuxconfig.org:
# virsh start server2.linuxconfig.org Domain server2.linuxconfig.org started
Check the state of all virtual machines:
# virsh list --all Id Name State ---------------------------------------------------- 1 server1.linuxconfig.org running 3 server2.linuxconfig.org running