In practice a sysadmin might replace 20 physical machines on an older network, with 2 physical machines, and 20 virtual machines (VMs). The 20 VMs would be installed on a shared storage volume, formatted with a clustered file system such as GFS2, for mounting by the 2 physical machines.
|qemu-kvm||Main KVM package|
|libvirt-client||The virsh command and clients API to manage VMs|
|virt-install||CLIs for creating VMs|
|virt-manager||GUI VM admin tool|
|virt-top||CLI for VM stats|
|virt-viewer||GUI console to connect to VMs|
As an alternative to installing the packages individually, can just install the Virtualization Host and Virtualization Client package groups.
yum group install "Virtualization Host" "Virtualization Client"
Verify the appropriate kernel modules have been loaded.
# lsmod | grep kvm kvm_intel 200704 0 kvm 593920 1 kvm_intel
VM storage images are generally huge files. It wise to dedicate a partition or logical volume to the
/var/lib/libvirt/images directory. Another option is to symlink this somehwere that has ample capacity (note the SELinux contexts must be setup).
$ mkdir ~/kvm $ su - root # semanage fcontext -a -t virt_image_t '/home/ben/kvm(/.*)?' # restorecon /home/ben/kvm # rmdir /var/lib/libvirt/images # ln -s /home/ben/kvm /var/lib/libvirt/images
Virtual Network Interfaces
Virtual NICs can connect to Virtual Networks (not to be confused with each other). Each virtual network is associated to a virtual switch, such as
virbr0. Cool! These virtual switches operate in NAT mode (default) when traffic is forwarded on to the physical host. Four types of Virtual NICs:
- Bridge: bridges physical and virtual interface.
- Bond: Combines multiple interfaces into a single logical for redundancy.
- Ethernet: New inteface.
- VLAN: An interface with IEEE 802.1Q VLAN tagging.
Kickstart is the Red Hat system for automated installations, that works from an answers file.