Wednesday, December 7, 2011

Build a Linux PXE server to provision Linux and Windows Servers

Windows Deployment Service (WDS)/SCCM is the traditional way to provision  Windows servers, However if you need to provision both Linux and Windows Servers, it would be nice to have a all-in-one server. Before Windows Preinstallation Environment (WinPE) was developed, disk imaging tool like ghost is used to deploy syspreped windows OS as non-windows based provision solution. WinPE is part of Windows Automated Installation Kit(WAIK), it includes, imagex, a tool to capture image on file system level rather than raw sector level.

The PXE Server presented here has the following features:

- Support any PXE capable Linux distribution and most Windows versions: 2000/2003/XP/Vista/7/2008/2008 R2. Potentially, support any other PXE capable server e.g Solaris
- Zero touch installation/full automation
- Dynamic loading configuration using CGI script of your choice PHP/Perl ...
- Downloading kernel/images over http which is more reliable and faster than tftp, additionally, http makes it possible to provision over remote site

Environment setup

7 VMS in Virtualbox 4( for testing provision Centos 5.5, Windows 2003, and Windows 2008 R2)
- PXE server: Centos 5.5
- PXE Linux Client: Centos 5.5
- WAIK tools computer: Windows 2008 R2
- PXE Windows Client(imagex/sysprep target): Windows 2008 R2
- PXE Windows Client(imagex/sysprep target): Windows 2003 R2
- Imagex/sysprep source: Windows 2008 R2
- Imagex/sysprep source: Windows 2003 R2
- Select PCnet-fast III network adapter to support PXE boot
- Windows VM must have at least 1G RAM, because WinPE ISO memdisk will consume few hundreds of MB
- Setup samba share in PXEServer to store Windows imagex(.wim ) files,autoscript for disk partitioning/apply .wim image etc(autorun.bat).
Refer to
Just the filename parameter need to be set to:  filename "gpxelinux.0";
Install pxeserver(syslinux)
The original syslinux package in Centos 5.5 doesn't support memdisk, I use syslinux-4.03
Upgrade to syslinux-4.03 with RPM binary package, but the gpxelinux.0 need to customized and compiled from source.
gPXE/pxelinux backgroud
gPXE( or it is successor iPXE ( support dynamic configuration using any CGI script and support kernel/images loading over http.
Because gPXE/iPXE doesn't support memdisk, which is essential for loading winPE ISO image, we have to use pxelinux in syslinux. Fortunately, syslinux integrates gPXE, so we can switch between gPXE and pxelinux freely using CGI script. That is, use gPXE for Linux, use pxelinux for Windows
Compile customized gPXE in syslinux source file
$cd ${syslinux source}/gpxe/ 
$vi pxelinux.gpxe
set use-cached 0
dhcp net0
chain http://pxe-server/boot/home.php?mac=${net0/mac}
# "!gpxe" is interpreter, not a comment line 
# chain http://pxe-server/boot/home.php?mac=${net0/mac}?will pass the MAC address to a CGI script, which can generate individual configuration based on MAC address
#To use the DNS name, pxe-server, a working DNS server need to be advertised to DHCP client.
$cp gpxelinux.0 /tftpboot/
How does the CGI script work?

A CGI script, php in this example, retrieve the MAC address passed by gPXE request, lookup host-os mapping table, then generate PXE configuration dynamically.

#The configuration file to define which OS to apply based on MAC address
$cat ${wwwroot}/boot/hosts/host-os.conf 
#Mac               os
08:00:27:4d:4d:aa, centos-5.5-i386
08:00:27:b2:40:3e, windows-2008r2-x64

#Linux Server can use gPXE directly
$curl http://pxe-server/boot/home.php?mac=08:00:27:4d:4d:aa
kernel http://pxe-server/boot/os/centos-5.5-i386/pxeboot/vmlinuz ksdevice=link  ks=http://pxe-server/boot/hosts/linux-ks/08-00-27-4d-4d-aa.txt
initrd http://pxe-server/boot/os/centos-5.5-i386/pxeboot/initrd.img 

#Windows server has to rely on pxelinux to support memdisk(part of syslinux package)
$curl http://pxe-server/boot/home.php?mac=08:00:27:b2:40:3e
imgload pxelinux.0
boot pxelinux.0

#A pxelinux config is generated in the mean time 
$cat  /tftpboot/pxelinux.cfg/01-08-00-27-b2-40-3e 
default pe
label  pe
kernel http://pxe-server/boot/os/memdisk
append iso
initrd http://pxe-server/boot/os/w2k8_pe_x64.iso
Implementing Zero touch installation/full automation

Booting up the server via PXE is the first phrase of zero touch installation, OS level automation is done by Linux unattended install: e.g. Kickstart for Redhat Linux family or Windows unattended install:syspreped windows, startnet.cmd in winPE, autoscript in a network share
The following focus on Windows unattended install.
Download WAIK for Windows 7/Windows 2008 R2
How can you use WAIK for Windows 2008 R2 to deploy Windows2000/xp/2003
 It is true that you can't run setup.exe of Windows 2003 in 2008 R2 winPE, but we use imagex tool to capture files, so it works on most Windows OS.
Create winPE ISO
Install the WAIK  in WAIK tools computer
Steps to create winPE ISO
#Open the deployment tools command prompt
#amd64 is for 64bit, use x86 for 32bit
$\>copype.cmd amd64 C:\winpe_amd64
####Optional:Mount the wim file in order to add auto deploy script, you can skip this step to make it easier to get it going.
####BEGIN script customization
$\>imagex /mountrw c:\winpe_amd64\winpe.wim 1 c:\winpe_amd64\mount
#modify C:\winpe_amd64\mount\Windows\System32\starnet.cmd, add following lines below 'wpeinit'
REM -- Start
REM Mount Linux samba share
net use J: \\pxe-server\windows-media
REM go to sub-dir(dirname is the mac address) of the samba share and run the auto script
for /F  "usebackq tokens=2 delims=:"  %%i IN (`ipconfig /all ^| find /i "physical address" `) DO cd %%i
REM -- end
$\>imagex /unmount c:\winpe_amd64\mount /commit
#####END script customization
$\>copy "C:\Program Files\Windows AIK\Tools\amd64\imagex.exe"  C:\winpe_amd64\ISO\
$\>copy C:\winpe_amd64\winpe.wim C:\winpe_amd64\ISO\sources\boot.wim
$\>Oscdimg -n -bC:\winpe_amd64\ C:\winpe_amd64\ISO C:\winpe_amd64\winpe_amd64.iso

How to do sysprep in Windows 2003?
On imagex/sysprep source computer:
Download the latest sysprep tool:
WindowsServer2003-KB926028-v2-x86-ENU.exe /x to extract the file
Extract files in to c:\sysprep
Run setupmgr.exe to create answer file c:\sysprep\Sysprep.inf
Run sysprep /reseal to prepare the OS for imaging
How to do sysprep in Windows 2008 R2?
On WAIK tool computer:
Open Windows system image manager?in WAIK to create unattended answer file
Click New answer file?to select a windows catalogue file (.clg) in installation media \Deploy\Operating Systems\Windows Server 2008 R2 x64\sources\.
In the Windows images?panel, right click various parameters to add to answer file
Detailed instruction:
On imagex/sysprep source computer:
Retrieve above new answer file *.xml, Run sysprep /generalize /oobe /shutdown /unattend:unattend.xml?
Capture image in imagex/sysprep source computer
This is manual process, because it is once-off job
Once the imagex/sysprep source computer is shutdown, Reboot it with winpe_amd64.iso by mounting to CDROM or loading via PXE
#The files source is the partition with windows folder, It could be d:, because W2k8 assign c: to the small system partition by default, which  doesn't need to be captured.
$\>imagex /compress fast  /capture [c:|d:]  $sambashare:\boot.wim "w2k8 R2 64bit"
Copy the boot.wim to samba share, which will be used by imagex /apply.
Apply image in imagex/sysprep target computer
This need to be full automatic process, boot winpe_amd64.iso via PXE. Once winPE is initialized, it will mount the sambashare, cd to its own directory and run auorun.bat, which will partition disk and apply the image.

It is zero touch installation, no human intervention is needed, however, unlike kickstart, computer name/IP address etc can't be configured automatically. Well, in theory, you can specify the information in sysprep then re-capture image for each unique configuration, but it defeats the purpose of saving time in provision. The other way is fresh installation by giving answer file in samba share to setup.exe.
 But it can only be used for Visa/2008/7/2008 R2, because there is no winPE which support running setup.exe of pre-Vista Windows

$ ls $sambashare\08-00-27-b2-40-3e
autorun.bat  boot.wim  diskpart.txt
$ cat $sambashare\08-00-27-b2-40-3e\autorun.bat 
diskpart /s diskpart.txt
imagex /apply boot.wim 1 c: && bcdboot c:\windows /s c: && exit
#bcdboot c:\windows is not needed for pre-Vista Windows, but it does no harm.

It is done, if you have setup answer file properly, the imagex/sysprep target computer should be able to boot smoothly without any human intervention.
Issues  encountered:
Q: DNS name is not resolvable in gPXE.
A: Make sure set use-cached 0 is set in pxelinux.gpxe, then recompile
$vi pxelinux.gpxe
set use-cached 0
dhcp net0
chain http://pxe-server/boot/home.php?mac=${net0/mac}

Q: gPXE couldn't boot Linux kernel with error:Kernel panic not syncing: VFS: unable to mount root fs
A:Make sure imgfree is the first statement in Linux pxe config
 $curl http://pxe-server/boot/home.php?mac=08:00:27:4d:4d:aa
kernel http://pxe-server/boot/os/centos-5.5-i386/pxeboot/vmlinuz ksdevice=link  ks=http://pxe-server/boot/hosts/linux-ks/08-00-27-4d-4d-aa.txt
initrd http://pxe-server/boot/os/centos-5.5-i386/pxeboot/initrd.img

Q:Error in imagex /apply after booting winPE via PXE: Not Enough Server Storage is available to process is command
A: Make sure the Windows VM have at least 1G RAM, because winPE ISO will consume a few hundreds MB as memdisk

Q:What if the winPE doesn't recognize the device (RAID/NIC) with default drivers.
A:Add customize driver to winPE, refer to