6.4. Installing guests with PXE

This section covers the steps required to install guests with PXE. PXE guest installation requires a shared network device, also known as a network bridge. The procedures below covers creating a bridge and the steps required to utilize the bridge for PXE installation.

Create a new bridge
1. Create a new network script file in the /etc/sysconfig/network-scripts/ directory. This example creates a file named ifcfg-installation which makes a bridge named installation.
```
# cd /etc/sysconfig/network-scripts/
# vim ifcfg-installation
DEVICE=installation
TYPE=Bridge
BOOTPROTO=dhcp
ONBOOT=yes
```
  Warning
  The line, TYPE=Bridge, is case-sensitive. It must have uppercase 'B' and lower case 'ridge'.
2. Start the new bridge by restarting the network service. The ifup installation command can start the individual bridge but it is safer to test the entire network restarts properly.
```
# service network restart
```
3. There are no interfaces added to the new bridge yet. Use the brctl show command to view details about network bridges on the system.
```
# brctl show
bridge name     bridge id               STP enabled     interfaces
installation    8000.000000000000       no
virbr0          8000.000000000000       yes
```
  The virbr0 bridge is the default bridge used by libvirt for Network Address Translation (NAT) on the default Ethernet device.

Add an interface to the new bridge

Edit the configuration file for the interface. Add the BRIDGE parameter to the configuration file with the name of the bridge created in the previous steps.

# Intel Corporation Gigabit Network Connection
DEVICE=eth1
BRIDGE=installation
BOOTPROTO=dhcp
HWADDR=00:13:20:F7:6E:8E
ONBOOT=yes

After editing the configuration file, restart networking or reboot.

# service network restart

Verify the interface is attached with the brctl show command:

# brctl show
bridge name     bridge id               STP enabled     interfaces
installation    8000.001320f76e8e       no              eth1
virbr0          8000.000000000000       yes

Security configuration
Configure iptables to allow all traffic to be forwarded across the bridge.
```
# iptables -I FORWARD -m physdev --physdev-is-bridged -j ACCEPT
# service iptables save
# service iptables restart
```
Disable iptables on bridges
Alternatively, prevent bridged traffic from being processed by iptables rules. In /etc/sysctl.conf append the following lines:
```
net.bridge.bridge-nf-call-ip6tables = 0
net.bridge.bridge-nf-call-iptables = 0
net.bridge.bridge-nf-call-arptables = 0
```
Reload the kernel parameters configured with sysctl.
```
# sysctl -p /etc/sysctl.conf
```
Restart libvirt before the installation
Restart the libvirt daemon.
```
# service libvirtd reload
```

The bridge is configured, you can now begin an installation.

PXE installation with virt-install

For virt-install append the --network=bridge:installation installation parameter where installation is the name of your bridge. For PXE installations use the --pxe parameter.

Example 6.2. PXE installation with virt-install

# virt-install --hvm --connect qemu:///system \
    --network=bridge:installation --pxe\
    --name EL10 --ram=756 \
    --vcpus=4
    --os-type=linux --os-variant=rhel5
    --file=/var/lib/libvirt/images/EL10.img \

PXE installation with virt-manager

The steps below are the steps that vary from the standard virt-manager installation procedures.

Select PXE
Select PXE as the installation method.
Select the bridge
Select Shared physical device and select the bridge created in the previous procedure.
Start the installation
The installation is ready to start.

A DHCP request is sent and if a valid PXE server is found the guest installation processes will start.