PXE (Preboot Exceution Environment) combined with Kickstart enables fully automated, network-based operating system deployments. This guide details how to configure a CentOS 6.5 server to provision CentOS 7.3 systems without manual interaction—using HTTP for installation media delivery, DHCP for IP assignment, TFTP for boot file distribution, and a customized Kickstart configuration.

Core Components Overview

PXE is a standardized client-server interface that allows a machine to boot over the network before a OS loads. It relies on three key services:

• DHCP: Assigns an IP address and identifies the TFTP server and boot file (pxelinux.0)
• TFTP: Serves lightweight boot components: bootloader, kernel, and initramfs
• HTTP/FTP/NFS: Hosts the full OS installation tree and Kickstart script

Kickstart eliminates interactive prompts by supplying pre-defined answers—partitioning schemes, package selections, root passwords, network settings, and more—in a declarative cofniguration file (ks.cfg). When invoked during PXE boot, the installer applies these settings automatically.

Prerequisites & Environment

• Host OS: CentOS 6.5 (minimal install)
• Hypervisor: VMware Workstation (bridge networking mode)
• Server IP: 192.168.3.12
• Firewall: Disabled (iptables stopped)
• SELinux: Set to disabled

HTTP Repository Setup

Mount the CentOS 7.3 ISO and expose its contents via HTTP:

yum install -y httpd
mkdir -p /mnt/centos7
mount -o loop /path/to/CentOS-7-x86_64-Minimal.iso /mnt/centos7
cp -r /mnt/centos7/* /var/www/html/centos7/
service httpd start
chkconfig httpd on

TFTP Service Configuration

Install and enable TFTP through xinetd:

yum install -y tftp-server xinetd
sed -i 's/disable[[:space:]]*=[[:space:]]*yes/disable = no/' /etc/xinetd.d/tftp
service xinetd restart
chkconfig xinetd on

Populate the TFTP root directory:

yum install -y syslinux
cp /usr/share/syslinux/pxelinux.0 /var/lib/tftpboot/
cp /var/www/html/centos7/images/pxeboot/{vmlinuz,initrd.img} /var/lib/tftpboot/
cp /var/www/html/centos7/isolinux/vesamenu.c32 /var/lib/tftpboot/
cp /var/www/html/centos7/isolinux/*.msg /var/lib/tftpboot/

mkdir -p /var/lib/tftpboot/pxelinux.cfg
cp /var/www/html/centos7/isolinux/isolinux.cfg /var/lib/tftpboot/pxelinux.cfg/default

Edit /var/lib/tftpboot/pxelinux.cfg/default to define the auto-install menu entry:

default menu.c32
prompt 0
timeout 300

menu title Automated CentOS Installer

label ks
  menu label ^Deploy CentOS 7.3 (Auto)
  kernel vmlinuz
  append initrd=initrd.img inst.ks=http://192.168.3.12/centos7ks.cfg inst.ks.device=eth0

DHCP Server Configuration

Configure DHCP to direct PXE clients to the TFTP server and boot file:

yum install -y dhcp
cp /usr/share/doc/dhcp*/dhcpd.conf.sample /etc/dhcp/dhcpd.conf

# Edit /etc/dhcp/dhcpd.conf:
subnet 192.168.3.0 netmask 255.255.255.0 {
  range 192.168.3.100 192.168.3.200;
  option routers 192.168.3.1;
  option subnet-mask 255.255.255.0;
  filename "pxelinux.0";
  next-server 192.168.3.12;
  default-lease-time 21600;
  max-lease-time 43200;
}

Start the service:

service dhcpd start
chkconfig dhcpd on

Kickstart File Generation

For reproducibility and accuracy, derive centos7ks.cfg from an existing installation’s /root/anaconda-ks.cfg:

cp /root/anaconda-ks.cfg /var/www/html/centos7ks.cfg
chmod 644 /var/www/html/centos7ks.cfg

A minimal but functional example:

#version=RHEL7
install
url --url="http://192.168.3.12/centos7"
text
reboot
keyboard --vckeymap=us --xlayouts='us'
lang en_US.UTF-8
firewall --disabled
selinux --disabled
timezone Asia/Shanghai --isUtc
bootloader --location=mbr --boot-drive=sda --append="crashkernel=auto"

network --bootproto=dhcp --device=ens33 --onboot=on --ipv6=auto
rootpw --iscrypted $6$...truncated...
auth --enableshadow --passalgo=sha512

clearpart --all --initlabel
part /boot --fstype=xfs --size=300
part pv.100 --size=1 --grow
volgroup vg0 --pesize=4096 pv.100
logvol / --fstype=xfs --name=lv_root --vgname=vg0 --size=10240
logvol /data --fstype=xfs --name=lv_data --vgname=vg0 --size=20480
logvol swap --fstype=swap --name=lv_swap --vgname=vg0 --size=2048

%packages
@^minimal-environment
kexec-tools
%end

%addon com_redhat_kdump --enable --reserve-mb='auto'
%end

Key directives:

• reboot: Ensures automatic reboot post-installation
• clearpart --all --initlabel: Prevents manual intervention during disk formatting
• inst.ks in kernel args: Points the installer to the remote Kickstart file

Validation

Create a new VM with network adapter set to bridged mode and PXE boot enabled. On power-on, it will:

1. Obtain an IP via DHCP
2. Fetch pxelinux.0 via TFTP
3. Load kernel and initramfs
4. Retrieve and parse centos7ks.cfg over HTTP
5. Proceed unattended through partitioning, package installation, and finalization

Upon completion, verify disk layout matches the Kickstart specification using lsblk or df -h.