I typically run something like this after a fresh install

install_xcat.sh

#!/bin/sh
#  I typically run something like this after a fresh install

########################################
# What DISTRO are we installing on
########################################
release=rh6
ARCH=x86_64
DISTRO=centos6.4
ISO_DISTRO=CentOS6.4
ISO_ARCH=x86_64
DISTRO_VERS=6.4



########################################
#  CONFIGURE personal bashrc stuff
########################################
cat <<BASHRC>>~/.bash_profile
################ BEGIN  preferences 
  export PS1="\n[\[\e[1;36m\]\u\[\e[0m\]@\[\e[1;34m\]\H\[\e[0m\]] [\[\e[1;33m\]\d, \t\[\e[0m\]] [\[\e[1;31m\]\!\[\e[0m\]]\n\[\e[1;31m\]\[\e[0m\][\[\e[1;37m\]\w\[ \e[0m\]]\n\[\e[1;37m\]\\$\[\e[0m\] " 
  HISTSIZE=100000
  HISTFILESIZE=100000
  HISTTIMEFORMAT="[%F %T] "
  HISTCONTROL=erasedups
  export EDITOR=vi
  set filec
  set autolist
################ END  preferences 
BASHRC
# source ~/.bash_profile

##############################################
# ADD NETOWRKS  Management, Compute and DATA
#   in my case eth0 is the world network
#   that connects to the DMZ vlan
##############################################
cat <<NIC>>/etc/sysconfig/network-script/ifcfg-mgmt
DEVICE=eth1
ONBOOT=yes
BOOTPROTO=static
IPADDR=10.5.1.1
NETMASK=255.255.255.0
PEERDNS=no
#HWADDR=08:00:27:5B:56:72
NIC
cat <<NIC>>/etc/sysconfig/network-script/ifcfg-cmpt
DEVICE=eth2
ONBOOT=yes
BOOTPROTO=static
IPADDR=10.5.2.1
NETMASK=255.255.255.0
PEERDNS=no
#HWADDR=08:00:27:5B:56:53
NIC
cat <<NIC>>/etc/sysconfig/network-script/ifcfg-data
DEVICE=eth3
ONBOOT=yes
BOOTPROTO=static
IPADDR=10.5.3.1
NETMASK=255.255.255.0
PEERDNS=no
#HWADDR=08:00:27:5B:56:54
NIC


########################################
# install xcat packages
########################################
yum erase tftp-server.*
cd /etc/yum.repos.d 
wget http://xcat.sourceforge.net/yum/xcat-core/xCAT-core.repo 
wget http://xcat.sourceforge.net/yum/xcat-dep/${release}/${ARCH}/xCAT-dep.repo
# rpm -Uvh http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm



  ########################################
	# install RPM KEYS -- very important 
	########################################
	mount /dev/cdrom /mnt &&
	for key in /mnt/RPM-GPG-KEY*
	do
		rpm --import $key
	done


	########################################
	# install xcat packages
	########################################
 yum clean metadata 
 yum -y install xCAT
 yum -y install yaboot-xcat.noarch
 yum -y install net-snmp-utils
 yum erase tftp-server.*
 yum -y install xCAT-rmc.noarch 
 yum -y install expect
 yum -y install yum-downloadonly
 yum -y install ntp net-snmp-utils
 yum -y install lynx  xauth
 yum -y clean metadata 
 yum -y install xCAT busybox-anaconda
 yum -y install yaboot-xcat.noarch


########################################
 source /etc/profile.d/xcat.sh
 tabdump site




########################################
#	SET UP AN NTP SERVER
########################################
\cp -f /usr/share/zoneinfo/America/Montreal /etc/localtime
ntpdate -q 0.centos.pool.ntp.org
ntpdate -bs 0.centos.pool.ntp.org
hwclock -w
chkconfig --level 345 ntpd on

cat <<EOF>/etc/ntp.conf
server 127.127.1.0
fudge   127.127.1.0 stratum 10
driftfile /var/lib/ntp/drift
keys /etc/ntp/keys
EOF
service ntpd restart
#


########################################
#	BUILD A CENTOS MIRROR
########################################
#  also see https://gist.github.com/BlackMaria/5646121
copycd-cdrom -a $ARCH -o centos6 



########################################
#	FINALLY
########################################
echo if this worked you should see the default config info after this text
tabdump site

#  And now you can make some nodes
# https://gist.github.com/BlackMaria/5645997