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Zim3r
Asked: 2012-06-30 12:10:58 +0800 CST

Change amount of Ram and CPU cores in KVM

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How can I Change amount of Ram and CPU cores for a virtual machine in KVM that is already created? Thanks

virtualization kvm-virtualization vps

4 Answers

  1. For offline configuration:

    To increase the number of CPUs:

    virsh setvcpus <vm_name> <vcpu_count> --config

    If you get an error that you exceeded the maximum number, first do:

    virsh setvcpus <vm_name> <vcpu_count> --config --maximum

    Then repeat the above:

    virsh setvcpus <vm_name> <vcpu_count> --config

    To increase the memory size:

    virsh setmaxmem <vm_name> <memsize> --config
virsh setmem <vm_name> <memsize> --config

    For online configuration:

    You can set the vCPU and memory while the VM is running with --current instead of --config, but the new numbers has to be within the maximum values already set. You can not set these maximum numbers while the VM is running. You will have to shutdown the VM with virsh shutdown <vm_name>, use the above command and start back the VM with virsh start <vm_name>.

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  2. Best Answer

    You can edit its XML from command-line with:

    virsh edit name_vhost

    Then, you only have to search the <memory> tag and modify it

    Keep in mind that the memory allocation is in kilobytes, so to allocate 512MB of memory, use 512 * 1024, or 524288.

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  3. You can edit the VM settings in virt-manager or in cli by changing the XML in virsh edit VMNAME

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  4. To increase the maximum amount of memory that can be allocated to the VM you have to increase the maximum memory limit, power off the VM, increase the memory allocated, the start the VM. There's a step-by-step guide here:

    http://earlruby.org/2014/05/increase-a-vms-available-memory-with-virsh/

    To get more VCPUs you have to edit the virsh XML file and restart the VM. There's a step-by-step guide to do this here:

    http://earlruby.org/2014/05/increase-a-vms-vcpu-count-with-virsh/

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