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boot from a file backed wim


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#1 MedEvil

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Posted 13 March 2011 - 03:17 PM

I'm looking for a way to use .wim also on low RAM systems.

Idealy, i would like to have a dual boot option, .wim in RAM and wim on CDVD/USB-Stick/HDD.

So far, i havn't found a wim script in any project, which offers such a feature.

Is this because it can't be done or because nobody was yet interested in it?


:whistling:

#2 amalux

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Posted 13 March 2011 - 04:05 PM

You can have multi-boot iso/images from UFD/USB/HDD with wim/ram loaded and non-wim/non-ram loaded options but I see no way to have wim/non-ram on CDVD; where does the wim expand to?

#3 MedEvil

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Posted 13 March 2011 - 04:31 PM

The wim should expand to nowhere. It should be used right from the drive.
A setup like that is possible with hdd-images.

But i have too little knowledge about Vista/Win7, to know, if it can be done with .wim too.

:whistling:

#4 amalux

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Posted 13 March 2011 - 04:43 PM

The wim should expand to nowhere. It should be used right from the drive.
A setup like that is possible with hdd-images.

The hdd-images (images on HDD) are expanding to RAM just like WIM on CD expands to RAM. The WIM must expand to be bootable.

#5 MedEvil

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Posted 13 March 2011 - 04:55 PM

That's one way to do it.
But one can also use a hdd-image(image of a hdd) straight from a CDVD, without loading it into RAM first.

:whistling:

#6 amalux

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Posted 13 March 2011 - 05:07 PM

But one can also use a hdd-image(image of a hdd) straight from a CDVD, without loading it into RAM first.

A WIM image? Not as far as I know but...

#7 MedEvil

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Posted 13 March 2011 - 05:15 PM

I don't know, if it can be done with a .wim image, that's why i ask, but it can be done with a default hdd image, like it is also used for ram-booting.

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#8 amalux

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Posted 13 March 2011 - 05:19 PM

I don't know, if it can be done with a .wim image, that's why i ask...

Deja vu?

I'm sure that Jaclaz will have explained at the time that part of the reason is because WIM images lack a bootable filesystem. That's why a ramdisk needs to be created, the contents of the WIM loaded onto it, and then the ramdisk booted.

Regards,
Galapo.


WIM images need to be deployed to an existing volume or partition as the toolset does not create low-level disk structures such as partitions, nor does it format them.


http://en.wikipedia...._Imaging_Format

#9 MedEvil

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Posted 13 March 2011 - 05:41 PM

I'm sure that Jaclaz will have explained at the time that part of the reason is because WIM images lack a bootable filesystem. That's why a ramdisk needs to be created, the contents of the WIM loaded onto it, and then the ramdisk booted.

Regards,
Galapo.

I'm pretty sure, that's not the way it works.
Else booting a .wim into RAM and booting a .img into RAM, which contain the same files, would require the same amount of ram. But one of the advantages of .wim over traditional .img is the better compression.

If i'm wrong and you're right, this whole question would become immediately pointless.

:cheers:

#10 maanu

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Posted 13 March 2011 - 05:46 PM

.wim expands to RAM . it is sure . a ramdisk mounts it on the fly to be make it bootable for the system,

but according to some of my chinese friends , a wim based image is MORE efficient on low ram systems then ANY OTHER format like .IMG etc .

#11 MedEvil

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Posted 14 March 2011 - 12:05 AM

I checked in a Win7PE and drive x: (wim) does not show up in drivemanager.
It behaves more like ImDisk and not like M$ramdisk.sys.

Since i see no reason, why M$ should throw away it's own ramdisk driver, to get one, which works differently, but serves the same purpose. I don't think that a ramdisk is first created and then the .wim file loaded onto it.
Besides, shouldn't get such a ramdisk a own drive letter?

Also extracting the contents of the .wim file to the ramdisk is out of the question. This would increase the required space for the files, which is just not consistent with comparisons between a SDI-booted PE and a wim-booted PE.

:cheers:

#12 MedEvil

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Posted 14 March 2011 - 12:35 AM

Is WimFltr.sys, the driver used to mount a .wim file in a running Windows, the same driver that Windows uses to boot froma .wim?

:cheers:

#13 ilko

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Posted 14 March 2011 - 12:45 AM

As far as I remember boot.wim for example can be extracted to say root of an USB stick and bootmgr can boot the extracted winload.exe just fine. Mind you, ~140MB boot.wim only second index extracts to, if I recall correctly, 650-700 MB. This way bootmgr would not create RAM disk with boot.wim contents in it, but would rather load winload.exe directly on the USB stick. BCD must be edited and "device" and "osdevice" should be set to BOOT.

Bcdedit –store E:\boot\BCD –set <GUID> osdevice boot

Bcdedit –store E:\boot\BCD –set <GUID> device boot

Just an idea, may serve the purpose and worth a little digging, although not quite sure what the real gain in terms of RAM usage would be, plus if booting from USB the necessary changes for the USB drivers should be made.

Added: Rereading topic title, the above written seems well off topic. :cheers:

#14 cdob

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Posted 14 March 2011 - 04:59 PM

I don't think that a ramdisk is first created and then the .wim file loaded onto it.

Manufactuer describes How Booting into a Boot Image Works




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