We have a VM Linux server, where the hot add feature is disabled in VCenter.

For now, we can't power off the machine, and the feature is disable, so we can't add memory resources to the machine.

So do you have any idea how to enable the hot add feature without powering off the Linux redhat machine ?

2 Answers 2


It cannot be done. You'll have to power off the VM at some point, and enable memory (and CPU if you like) hot add.


In the short term, you can add swap to your VM, to give more resources without a reboot. This is only an interim workaround though, and will not be as fast as real ram.

In VMWare? No this is not possible. It's not the client OS stopping you, its your virtualisation platform.

It is "kind-of" possible in xcp-ng but only up to a specific number that you set before boot.

So a VM can be started with 2 CPUs and 2 GB ram, which can be increased provided you set the maximum numbers before boot. Eg:

Screenshot of xcp-ng console for CPU properties

Screenshot of xcp-ng console for memory properties of an instance


  • Maximum memory can be no more than 4x the boot memory.
  • CPUs maximum is 32, and if the physical host has less, then the extra are faked which hurts performance
  • Your OS has to support hot-add (most linux distros do)

And of course you need to run xcpng, not vmware.

  • Your answer is irrelevant, xcp-ng is another product based on Xen. The screenshots also are from xcp-ng client. It's perfectly possibly to hot-add memory and CPU on VMware, but it must be set when the VM is powered off. Adding swap is a nice point to mention though.
    – Krackout
    Commented Jun 29, 2020 at 6:00
  • @Krackout fair enough - editing to clarify the point.
    – Criggie
    Commented Jun 29, 2020 at 6:10

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