Category: OS


KVM: Virtual Bridge (virbr0) is NOT needed! I show you how to remove it :)

Filed Under: libvirt / KVM, Linux, OS, virtualization by Jason L Froebe — Leave a comment
November 28, 2011

for KVM, using an actual network bridge is desired for performance over NAT. There is a virtual bridge used by XEN (virbr0) that you won’t need.
To disable it:

$ virsh net-destroy default
$ virsh net-undefine default

# If Redhat based distro:
$ service libvirt-bin stop
# if Debian/Ubuntu based distro:
$ service libvirtd restart  

$ ifconfig
 

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Getting a permission denied for your home directory while logging in but you can cd to it no problem?

Filed Under: Linux, OS by Jason L Froebe — Leave a comment
November 28, 2011

It is likely SELinux trying to keep you safe.  Just run:

$ restorecon /home

It will correct the SELinux flags on the /home directory.

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if you’re unable to install the broadcom sta driver on ubuntu 11.04… we have the answer

Filed Under: Linux, OS by Jason L Froebe — Leave a comment
April 29, 2011

if you’re unable to install the broadcom sta driver on ubuntu 11.04, fire up synaptic and reinstall bcmwl-kernel-source

2011-04-29 18:29:50,089 WARNING: /sys/module/wl/drivers does not exist, cannot rebind wl driver

it should work now :)

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Comparing Linux huge memory pages & Kernel Samepage Merging for KVM virtualization

Filed Under: Linux, OS, Proxmox VE, virtualization, Windows by Jason L Froebe — Leave a comment
April 7, 2011

A quick test (so take it with a grain of salt):

  1. Huge pages is slightly faster than not using huge pages (~10% with 4 winxp virtual machines copying 512MB from one memory location to another).
  2. KSM is slightly slower then not using KSM (~5% with 4 winxp virtual machines copying 512MB from one memory location to another).

So, at first glance it would appear that we can use a loose rule of thumb:

  1. to consolidate the maximum number of machines, use KSM as it will allow you to over commit the amount of memory on your box.
    1. Risk: if the memory pages are significantly different, you may start swapping in a very bad way. This is where monitoring comes in
  2. to give the best performance to a number of machines, use huge memory pages.. does not allow you to over commit
    1. Risk: if you don’t leave enough memory for the host os, you can crash your machine. This is also where monitoring comes in
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Proxmox VE 1.8 and KVM: Adding sound to your virtual machines!

Filed Under: How To, Linux, OS, Proxmox VE, virtualization, Windows by Jason L Froebe — Leave a comment
April 7, 2011

This assumes that your host machine has a sound card! :)

Add the args line in your /etc/qemu-server/<vm id>.conf file should give you sound:

args: -soundhw

On my Proxmox VE 1.8, I have several virtual audio devices available.   I’ve had the best luck with ac97 with Windows XP/Vista and Win7.

red:/etc/qemu-server# kvm -soundhw ‘?’
Valid sound card names (comma separated):
pcspk       PC speaker
sb16        Creative Sound Blaster 16
ac97        Intel 82801AA AC97 Audio
es1370      ENSONIQ AudioPCI ES1370
hda         Intel HD Audio

-soundhw all will enable all of the above

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