Automating Xen Hypervisor VM Deployments Using virt-install

When managing standalone Xen or KVM hypervisors in enterprise data centers, relying on graphical virtual machine managers is highly inefficient during large-scale deployments. Mastering the command-line virt-install utility allows sysadmins to script and provision virtual machines instantly.

In this guide, I will walk you through configuring Linux network bridges (ifcfg-br0), provisioning Hardware Virtual Machine (HVM) and paravirtualized guests using virt-install, allocating raw storage disks, and mounting installation media over local directories and HTTP trees.

Prerequisites

You will need an Enterprise Linux hypervisor with root privileges, configured with libvirt and virt-install utilities, alongside available ISO installation media.

---

Step 1: Configuring Hypervisor Network Bridging (ifcfg-br0)

Before launching virtual machines, configure a dedicated network bridge (br0) on your hypervisor to allow guest VMs to attach directly to your local subnet.

# Backup existing interface configuration
cp /etc/sysconfig/network-scripts/ifcfg-bond0 /etc/sysconfig/network-scripts/ifcfg-br0

Update /etc/sysconfig/network-scripts/ifcfg-br0:

# /etc/sysconfig/network-scripts/ifcfg-br0
DEVICE="br0"
NM_CONTROLLED="no"
ONBOOT="yes"
TYPE="Bridge"
BOOTPROTO="none"
IPADDR="192.168.0.50"
PREFIX="24"
GATEWAY="192.168.0.1"

Restart networking to activate the bridge:

service network restart
brctl show

---

Step 2: Provisioning HVM Guests via ISO Media

To launch a full Hardware Virtual Machine (HVM) guest booting from a local ISO image, execute the following virt-install command. This allocates 16 GB of RAM, provisions a 360 GB raw disk, attaches to our bridge, and exposes a VNC console.

# Launch HVM Guest VM from ISO
virt-install --name fmcivragpvm22 \
    --ram 16384 \
    --cdrom /root/CentOS-6.5-x86_64-bin-DVD1.iso \
    --disk path=/VirtualMachines/fmcivragpvm22/disk.img,size=360,format=raw,sparse=false \
    --network bridge=br1 \
    --graphics vnc,listen=0.0.0.0 \
    --os-type=linux --os-variant=rhel6 \
    --hvm \
    --boot cdrom,hd

---

Step 3: Provisioning Paravirtualized Guests via Local Directory

If mounting installation media over a local directory (/mnt/centos/), provision a lightweight paravirtualized guest without graphical overhead (--graphics none):

# Launch Paravirtualized Guest from local directory tree
virt-install --name agent \
    --ram 4096 \
    --location=/mnt/centos \
    --disk path=/VirtualMachines/agent/disk.img,size=20,format=raw \
    --network bridge=br0 \
    --graphics none \
    --os-type=linux --os-variant=rhel6

---

Step 4: Provisioning Enterprise VMs via HTTP Installation Trees

When provisioning enterprise servers across multiple data centers, you can direct virt-install to pull OS installation trees over HTTP, assigning dual vCPUs and attaching directly to Spice graphical consoles.

# Launch VM pulling installation media over HTTP
virt-install \
   --name=guest1-rhel5-64 \
   --file=/var/lib/libvirt/images/guest1-rhel5-64.dsk \
   --file-size=8 \
   --nonsparse --graphics spice \
   --vcpus=2 --ram=2048 \
   --location=http://example1.com/installation_tree/RHEL5.6-Server-x86_64/os \
   --network bridge=br0 \
   --os-type=linux \
   --os-variant=rhel5.4

References

• Installing Xen 4 with Libvirt on CentOS
• Xen Official Configuration File Options