Tiny PXE Server

Multiple WinPE

It's possible to setup a PXE server to boot more than one version of WinPE - one method was covered in the wimboot section of this guide (here). It's also possible to use a BCD Store with multiple entries as an alternative to wimboot - this is covered below.

WinPE operating system files are contained in a .wim file - despite most instructions specifying the use of boot.wim the name of the .wim file is irrelevant. One of the main reasons for using boot.wim (in the path \sources\boot.wim) is convenience - the BCD Store that ships with WinPE usually uses this path and it saves building a new store. Provided that the BCD store contains a corresponding entry for the file an alternative name (to boot.wim) and path can be used.

The majority of rules applying to WinPE boot files and file paths on other media also apply to PXE Booting - with some exceptions -

The device type (e.g. ramdisksdidevice) must be set as boot - not partition, locate, etc.

The boot device (e.g. ramdisksdidevice boot) is the TFTP root directory and any paths specifed (e.g. ramdisksdipath \boot\boot.sdi) are relative to the TFTP root directory (e.g. C:\pxesrv\files\boot\boot.sdi ).

The path to the BCD store when booting a client system with UEFI firmware might be different. The default path to the BCD store is usually \EFI\microsoft\boot\BCD - this still applies if PXE Booting a Windows 7 based WinPE (WinPE 3.*), however a Windows 8 based WinPE (WinPE 4.0/5.*) will use the same path/file as systems with BIOS firmware (\boot\BCD).

The following sections are covered in this page -

boot.sdi
Fonts
Improve Loading Speeds

BCD Store examples (each section includes a link to a sample batch file used to create the store and a link to download the BCD) -

boot.wim (BIOS)
boot.wim (UEFI)
boot.wim (BIOS & UEFI)
x86.wim and x64.wim (BIOS)
x86.wim and x64.wim (UEFI)
x86.wim and x64.wim (BIOS & UEFI)

My personal preference is to keep all WinPE files in one directory - all of the BCD stores in this section consequently use the \boot path for both .sdi and .wim files.

Fonts

Some font files may be required in order to display error messages. When booting WinPE via PXE the Windows boot loader boot.exe will attempt to load \boot\fonts\wgl4_boot.ttf - if this file is missing WinPE will still boot, however there will be an error in the Tiny PXE Server log. E.g. - TFTPd:DoReadFile OpenError:\Boot\Fonts\wgl4_boot.ttf Cannot open file "E:\pxesrv_ISO\root\pxesrv\files\Boot\Fonts\wgl4_boot.ttf". The system cannot find the path specified

Based on information on the wimboot website (see here) the following font files are required -

\Boot\Fonts\segmono_boot.ttf
\Boot\Fonts\segoe_slboot.ttf
\Boot\Fonts\segoen_slboot.ttf
\Boot\Fonts\wgl4_boot.ttf

boot.sdi

As stated previously, the WinPE operating system files are contained in a .wim file. The ramdisk used to mount the .wim file so that the filesystem is accessible once WinPE has booted is contained in an .sdi file - usually \boot\boot.sdi. Again, this filename and path can be changed as long as the BCD store contains a corresponding entry. In my own tests I have been able to use the same .sdi file for booting WinPE 3.*/4.0/5.* on UEFI and BIOS systems and have consequently used the \boot\boot.sdi file\path in the examples below out of ~~lazyness~~ convenience.

Improve Loading Speeds

It's possible to add additional settings to a BCD store to improve file transfer speeds when booting WinPE via TFTP. The following settings need to be added to the ramdisksdidevice entry in the BCD store -

ramdisktftpblocksize [integer]
ramdisktftpwindowsize [integer]

Supported values for ramdisktftpblocksize include -

ramdisktftpblocksize 1024
ramdisktftpblocksize 2048
ramdisktftpblocksize 4096
ramdisktftpblocksize 8192
ramdisktftpblocksize 16384 (? maximum recommended)
ramdisktftpblocksize 32768

The following information is from the Windows Deployment Services Deployment Guide -

"...The default TFTP block size value is 1432 bytes...We recommend that you go up in multiples (4096, 8192, 16384, and so on) and that you not set a value higher than 16384...."

Supported values for ramdisktftpwindowsize include -

ramdisktftpwindowsize 4 (? default value)
ramdisktftpwindowsize 8

Changing either of these settings may cause issues - depending on the network infrastructure. There are reports of issues with PXE booting in VMware using a RamDiskTFTPBlockSize larger than 1432.

"...VMware does not appear to support RamDiskTFTPBlockSize above 1432 due to no support to deal with IP Fragmentation. However, it has been found that it is much better to adjust RamDiskTFTPWindowSize instead of RamDiskTFTPBlockSize to speed up TFTP (reduces amount of ACKs required and does not cause IP Fragmentation). VMware and other vendors all appear to handle this scenario perfectly..."

I carried out some test to ascertain WinPE load speeds using a BCD Store containing four separate entries - for use on BIOS systems (download the BCD store here - batch file here). Menu options -

WinPE (boot.wim - BIOS) - ramdisktftpblocksize = 4096
WinPE (boot.wim - BIOS) - ramdisktftpblocksize = 8192
WinPE (boot.wim - BIOS) - ramdisktftpblocksize = 16384
WinPE (boot.wim - BIOS) - ramdisktftpblocksize = 32768

The following (approximate) boot times were recorded on a test system (time was recorded from selecting the menu entry until the "Windows is loading files..." screen closed) -

ramdisktftpblocksize 4096 = 34 seconds
ramdisktftpblocksize 8192 = 24 seconds
ramdisktftpblocksize 16384 = 19 seconds
ramdisktftpblocksize 32768 = 16 seconds

boot.wim (BIOS)

This BCD Store contains one entry for use on BIOS systems - download here (batch file - here). The following files are required -

boot.sdi (e.g. C:\pxesrv\files\boot\boot.sdi)
boot.wim (e.g. C:\pxesrv\files\boot\boot.wim)

boot.wim (UEFI)

This BCD Store contains one entry for use on UEFI systems - download here (batch file - here). The following files are required -

boot.sdi (e.g. C:\pxesrv\files\boot\boot.sdi)
boot.wim (e.g. C:\pxesrv\files\boot\boot.wim)

boot.wim (BIOS & UEFI)

This BCD Store contains two entries - one entry for use on BIOS systems (menu option WinPE (boot.wim - BIOS)) and one entry for use on UEFI systems (menu option WinPE (boot.wim - UEFI)). Download here (batch file - here). The following files are required -