[ipxe-devel] boot.wim overlay?

Andrew Bobulsky rulerof at gmail.com
Thu Aug 14 19:33:06 UTC 2014

Hello Oliver, Chandan,

On Thursday, August 14, 2014, Oliver Rath <rath at mglug.de> wrote:

> Hi Chandan!
> Am 14.08.2014 um 03:02 schrieb Chandan:
> > Oliver Rath <rath at ...> writes:
> >
> >>
> >> Hi list,
> >>
> >> taken from the howto
> >>
> http://ipxe.org/howto/winpe#windows_assessment_and_deployment_toolkit_adk
> > i
> >> Here my question. Could it be possible to load an additional file (i.e.
> >> boot-enhancements.wim), which is also extracted into the ramdisk as
> >> overlay? So the boot.wim-system could be customized dynamicly very easy.
> >> I.e.:
> >>
> >> ....
> >>
> >
> >
> > Hi Oliver
> >
> > Were you able to find answer to question below or were able to define the
> > solution? I also have similar requirements and would be interested to
> know
> > what you discovered about it.
> >
> Unfortunatly i wasnt able to use a kind of overlay mechanism. This seems
> only possible with initramfs-files (where it works fine). The problem
> is, that the loaded wim-file is then extracted to a ramdisk, which is
> started as boot-device. If I wanted to use i.e. a second wim-file as
> overlay, this has to be extracted "over"  the first file, which didnt
> work here.
> *Maybe* it is possible to extract a second wim-file near the first ono
> as i.e. Y: device, but i wasnt able to realize this.
> My Solution I now use is to include a part of the the needed files via
> wimmount (you can also use dism) before i boot it. This is needed if
> haven't the right network-drivers at boottime.
If you need to inject drivers, using DISM is my recommendation.  It'll
integrate your drivers into the registry and Windows Driver stores in the
way that "just works."  It's also particularly easy to do with the
Driverpacks packages.  I use a pretty basic PE that has the LAN driverpack
integrated into it, then reaches out to a server to figure out where to go
from there.  Haven't had a missing network connection on anything since I
packed them into my PE.

For modifying WIMs on the fly though, you should really take a good look a
wimlib-imagex: http://sourceforge.net/projects/wimlib/

Wimlib will let you effortlessly script file/folder changes into a WIM, and
if necessary, also allow you to use a one-liner to recompress the WIM; they
bloat with every change by default, which is annoying.  Handy for low-RAM
systems.  Also keeps you cross-platform if you don't want to (or
can't!) use Windows for your back end.

The documentation is pretty thorough, too.  You may be able to splice WIMs
together with it as you desire, but it'd be done server side of course.  My
personal preference (and previous implementations) is just be to keep a
base WIM with NIC drivers, and then have staging directories that you fill
out and pack into temporary copies at boot time, then serve those up to
iPXE.  Just gotta make sure your cache doesn't run away on you ;)

The rest of Oliver's suggestions are pretty standard practice in my

> For other files I attach a network device with i.e.
> net use K: \\myserver\mydir /user:myuser mypass
> inside of my wimboot-script.
> What is your usecase? For what requirements do you need it?
> Hth,
> Oliver

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