Shell check if a variable is a number (Integer)

#!/bin/bash
if ! [[ "${variable}" =~ ^[0-9]+$ ]]
then
    echo "This variable is not a integer"
else
    echo "This variable is a integer"
fi

Reference: http://stackoverflow.com/questions/806906/how-do-i-test-if-a-variable-is-a-number-in-bash

Get installed rpm and format output

rpm -qa | uniq | sort | xargs rpm -q --qf "%{NAME},%{VERSION},%{RELEASE}\n" | uniq

Dnsmasq settings

domain=wiwynn.com

##Random IP
#dhcp-range=172.16.0.201,172.16.0.300

##Only static IP
dhcp-range=172.16.0.0,static

##Router
#dhcp-option=3,172.16.0.1
dhcp-option=option:router,172.16.0.1

##Name server
#dhcp-option=6,172.16.0.1
dhcp-option=option:dns-server,172.16.0.1

##NTP server
#dhcp-option=42,172.16.0.1
dhcp-option=option:ntp-server,172.16.0.1

dhcp-lease-max=1000
dhcp-authoritative

##Bootp
dhcp-boot=pxelinux.0,172.16.0.1

##Static IP and hostname to MAC address
dhcp-host=00:26:2d:09:5e:c6,172.16.0.101,juju1

##Forward domain archive.ubuntu.com query to 8.8.8.8
server=/archive.ubuntu.com/8.8.8.8

##Bind all host in main.wiwynn.com to 172.16.0.1
address=/main.wiwynn.com/172.16.0.1

Check option parameter:
sudo dnsmasq --help dhcp

PXEBoot config

Content of pxe config ( /var/lib/tftpboot/pxelinux.cfg/default )

DEFAULT menu
PROMPT 0
MENU TITLE Cobbler | http://fedorahosted.org/cobbler
TIMEOUT 50
TOTALTIMEOUT 6000
ONTIMEOUT local

##Boot into local hard disk
LABEL local
        MENU LABEL (local)
        MENU DEFAULT
        LOCALBOOT -1

##Boot into busybox, the busybox is copied from ubuntu install iso.
LABEL busybox
        MENU LABEL busybox
        kernel /sources/busybox/linux
        append initrd=/sources/busybox/initrd.gz

##Boot into ubuntu desktop amd64 live environment.
##Can't install ubuntu from this mode.
LABEL ubuntu-1110-desktop-amd64
        MENU LABEL Ubuntu 11.10 desktop amd64
        kernel /sources/ubuntu/1110/desktop/amd64/vmlinuz
        append initrd=/sources/ubuntu/1110/desktop/amd64/initrd.lz boot=casper root=/dev/nfs netboot=nfs nfsroot=192.168.116.1:/var/lib/tftpboot/sources/ubuntu/1110/desktop/amd64/nfs

##Boot into ubuntu desktop i386 live environment.
##Can't install ubuntu from this mode.
LABEL ubuntu-1110-desktop-i386
        MENU LABEL Ubuntu 11.10 desktop i386
        kernel /sources/ubuntu/1110/desktop/i386/vmlinuz
        append initrd=/sources/ubuntu/1110/desktop/i386/initrd.lz boot=casper root=/dev/nfs netboot=nfs nfsroot=192.168.116.1:/var/lib/tftpboot/sources/ubuntu/1110/desktop/i386/nfs

Mount ISO for provide NFS data

sudo mount -t auto -o loop ubuntu-1110-desktop-amd64.iso /var/lib/tftpboot/sources/ubuntu/1110/desktop/amd64/nfs
sudo mount -t auto -o loop ubuntu-1110-desktop-i386.iso /var/lib/tftpboot/sources/ubuntu/1110/desktop/i386/nfs

Content of nfs config( /etc/exports )

/var/lib/tftpboot/sources/ubuntu/1110/desktop/amd64/nfs 192.168.116.0/24(async,no_root_squash,no_subtree_check,ro)
/var/lib/tftpboot/sources/ubuntu/1110/desktop/i386/nfs 192.168.116.0/24(async,no_root_squash,no_subtree_check,ro)