http://lonesysadmin.net/2013/03/26/preparing-linux-template-vms/

Shutdown the GUI, if there is one:

init 3

Clean out the junk:

yum clean all

logrotate -f /etc/logrotate.conf
rm -f /var/log/*-???????? /var/log/*.gz

cat /dev/null > /var/log/audit/audit.log
cat /dev/null > /var/log/wtmp

rm -f /etc/udev/rules.d/70*

sed -i ‘/^\(HWADDR\|UUID|BOOTPROTO\)=/d’ /etc/sysconfig/network-scripts/ifcfg-eth[012]
echo "BOOTPROTO=dhcp" > /etc/sysconfig/network-scripts/ifcfg-eth0

rm -rf /tmp/*
rm -rf /var/tmp/*

rm -rf /etc/ssh/*key*

rm -rf ~root/.bash_history
unset HISTFILE

This is an optional script for RHEL systems to zero out the filesystem.

Don't do this on thinly provisioned VMs.

UNTESTED

#!/bin/sh

# Determine the version of RHEL
COND=`grep -i Taroon /etc/redhat-release`
if [ "$COND" = "" ]; then
        export PREFIX="/usr/sbin"
else
        export PREFIX="/sbin"
fi

FileSystem=`grep ext /etc/mtab| awk -F" " '{ print $2 }'`

for i in $FileSystem
do
        echo $i
        number=`df -B 512 $i | awk -F" " '{print $3}' | grep -v Used`
        echo $number
        percent=$(echo "scale=0; $number * 98 / 100" | bc )
        echo $percent
        dd count=`echo $percent` if=/dev/zero of=`echo $i`/zf
        /bin/sync
        sleep 15
        rm -f $i/zf
done

VolumeGroup=`$PREFIX/vgdisplay | grep Name | awk -F" " '{ print $3 }'`

for j in $VolumeGroup
do
        echo $j
        $PREFIX/lvcreate -l `$PREFIX/vgdisplay $j | grep Free | awk -F" " '{ print $5 }'` -n zero $j
        if [ -a /dev/$j/zero ]; then
                cat /dev/zero > /dev/$j/zero
                /bin/sync
                sleep 15
                $PREFIX/lvremove -f /dev/$j/zero
        fi
done