Persistent cache in QEMU or librbd?

我們知道無論是 QEMU 或是 librbd 都有提供 writeback cache. 同時也有兩個明顯的效能議題: cache 的生命週期跟隨 QEMU process, 也就是說一旦 VM shutdown, cache 也就跟著消失. 多個 QEMU process 間無法共享 cache, 而這在 »

Set up port-forwarding via libvirt's hook

It’s a bad idea using one file to maintain all port-forwarding rules for VMs. In such a traditional environment (without SDN I mean), consider libvirt’s hook mechanism as a more modular way.

For Ubuntu, edit /etc/libvirt/hooks/qemu and then restart the libvirt-bin service.


virsh error: Cannot allocate memory

Today I was trying to increase memory size on a qemu-kvm hosted VM. My plan was as simple as shut it down and then change memory setting via virsh edit <VMName>, but both virsh edit and virsh start throws the same error message:

error: cannot fork child process: Cannot allocate memory


Directly access the file system inside a VM disk image

Consider a situation that you want to change some settings i.e. edit some files in VM, it’ll be nice if you don’t have to boot it up then log in to make some changes. So the question becomes how to access the file system inside the VM disk image file?