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Revision as of 04:12, 7 September 2009 by Dale (talk | contribs)


In this section, we cover discussion of Fedora virtualization technologies on the @fedora-virt and @fedora-xen-list lists.

Contributing Writer: Dale Bewley

Fedora Virtualization List

This section contains the discussion happening on the fedora-virt list.

KSM Tuning Service

A new feature for Fedora 12, Kernel Samepage Merging[1], enables KVM guest virtual machines to share identical memory pages. This is especially useful when running multiple guests from the same or similar base operating system image. Because memory is shared, the combined memory usage of the guests is reduced. KSM works by scanning memory, looking for identical pages.

Dan Kenigsberg posted[2] a KSM control daemon in a "simple script that controls whether (and with what vigor) should ksm search duplicated memory pages."

"An unattended host running a variable number of qemu-kvm's needs to tune ksm automatically, since when memory is tight, it's better to spend more cpu on merging pages. In more relaxed cases, it's just a waste of time."

Host Iptables Settings for Bridged Guests

Mark McLoughlin pointed[1] out that the recommended[2] means of configuring iptables on the host to allow traffic to pass to a bridged guest is to disable netfilter on the bridge altogether.

 # cat >> /etc/sysctl.conf <<EOF
 net.bridge.bridge-nf-call-ip6tables = 0
 net.bridge.bridge-nf-call-iptables = 0
 net.bridge.bridge-nf-call-arptables = 0
 # sysctl -p /etc/sysctl.conf

This "will be the default with Fedora 12."

Fedora Xen List

This section contains the discussion happening on the fedora-xen list.

Xen Domain0 Kernels

Until support for pv_ops[1] is added to the upstream kernel (F13?), it takes some twiddling to host Xen guests on Fedora. Even then it isn't recommended for anything more than experimentation at this time. More adventurous users are reporting some success with experimental kernels and running a Xen dom0.[2] [3] [4]

Current dom0 kernel options include building[5] one from Jeremy Fitzhardinge's git repository or installing[6] Brian Young's RPM.