Article ID: 111221, created on May 3, 2011, last review on May 9, 2014

  • Applies to:
  • Virtuozzo hypervisor 5.0


Hot-added CPUs do not automatically appear in some SLES 11 guest operating systems configuration.
If you hot add extra CPUs to a virtual machine while it is running, they normally should appear in the *.pvs file, PMC, PVA, and in the guest operating system interface. In Linux virtual machines however, the additional CPUs are not automatically activated, i.e. they do not appear in the output of programs like top, that only list active processors.


A processor added using hot-add technology must first be activated in Linux guest before it can be used. To automate the process, create a file called /etc/udev/rules.d/99-psbm-hotaddcpu.rules in your virtual machine with the following content:

# Automatically put hot-added processors to online state.

ACTION=="add", SUBSYSTEM=="cpu", ATTR{online}="1"

After this moment all processors hot-added to this virtual machine will be activated automatically.

If you have already hot-added a processor, you may activate it manually by running this command as root:

# for a in /sys/devices/system/cpu/cpu*/online; do echo "1" > "$a"; done

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