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 Can I set up a ramdrive 4 iso boot?.....
post Jun 10 2010, 11:22 AM
Post #1
Technotika
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Hi Guys,
This forum is great and have learnt loads recently, and have successfully created some awesome usb keys for trouble shooting and repairing PC's.
However now I am where I want to be with that, I have turned my attentions towards applying my "lmtd skills" rolleyes.gif towards "USB'ing" things at work.

So far I can boot ISO's using grub4dos and syslinux quite happily, with a bit of tweaking here and there, However my latest project falls flat when it comes to the iso images I use at work.
We have a handful of different PC's that we have dvd ISO's knocking about all over the place.
We are forever burning the iso's to dvd and the office is just a mess with dvd's that work, that dont and its just a pain. USB sticks and grub4dos to the rescue I feel tongue.gif

The plan is to set up a nice USB with a grub/syslinux (or both if needed) with menus that let you select the appropriate image for the machine you are building/rebuilding. A classic use of this kind of system I feel.

Now so far I have the iso's on USB and have done a simple iso map command using "g4dos"and it goes through the process of loading but quickly fails because the iso, if being run from a dvd drive, loads a ramdrive "Q" to action something then load a GHOST image down on the system and away it goes.

I feel I can get this to work if I can apply some sort of third party ramdrive system (maybe firadisk, imdisk? from initial reading round) to the iso booting process.

The DVD's load a basic dos boot system first the load this ramdrive where they do something to get the PC name out of the bios then update the SYSPREP file so the ghost file can pick up the correct computer name.

I am quite sure if I can have some sort of ramdrive mapped as Q I can complete this task maybe just using the iso's etc.

Hope that makes sense. If it's something anyone has experience of please let me know or point me to a thread I may not have found. Other wise I can post more info if needed.

Thanks!!

smile.gif


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post Jun 10 2010, 07:17 PM
Post #11
Technotika
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PHEW GOT PAST THE err 60 " CONTIG" PROBLEM - reformatted and copied test iso over - NOW Booting but got the show stopper on a screen shot now for you to see, used a floppy image as suggested but I think this will make it clearer when you see for real what I mean....fingers x'd!!!

title test
map /winb98se.IMA (fd0)
map (hd0,0)/SR3.1_Thin_image.iso (hd32)
map --hook
chainloader (hd32)
boot



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post Jun 10 2010, 07:46 PM
Post #12
Sha0
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QUOTE (Technotika @ Jun 10 2010, 03:17 PM) *
...
title test
map /winb98se.IMA (fd0)
map (hd0,0)/SR3.1_Thin_image.iso (hd32)
map --hook
chainloader (hd32)
boot

Note that you are not making use of the floppy image here, since you are directly chaining to the emulated CD. This means that whatever boot image is in that .ISO is being chained to. I think you might be interested in using a different .ISO viewer so you can see and extract this boot file. I believe that you will find it to itself be a floppy disk image.

I do believe that what you need to do at this point is extract the floppy image from the .ISO (find it, first), then open that floppy image, inject ElTorito.sys, give it an entry in the Config.Sys file, then re-master your .ISO using that re-mastered floppy image. OR: Extract the floppy image, use that in your (fd0) mapping, then chain (fd0) instead of (hd32).
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Technotika
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post Jun 10 2010, 09:38 PM
Post #13
Technotika
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ok got some where more but still just out of reach.....here's where I have been,

1.) Totally understand there MUST be floppy image or boot files hiding in that iso somewhere for it to boot. The best way from your info
is to get that out, ammend it and re compile ISO to just boot the ISO.
2.) Installed a bunch of ISO apps and nothing showed it.
3.) Finally came across BBIE.EXE (http://www.nu2.nu/bbie/) and got the BIN file out. With WINIMAGE I did these 2 things....

a.) Injected the "ElTorito.sys" (http://www.boot-land.net/forums/index.php?showtopic=9950&hl=ElTorito.sys) file into the 1.40mb extracted boot image. So it now looks like.........



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b.) Made an entry in the config.sys. So it now looks like........


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So...........with all these in correct (I Hope?) I realised I could try your original suggestion of (below) , as all the right things were in place.

CODE
map /dos.vfd (fd0)
map /SR3_1_Thin_image.iso (hd32)
map --hook
root (fd0)
chainloader /io.sys
boot

However now get this error, notice some eltorito entrys!!
Something tells me I'm nearly there, perhaps this entry in config.sys needs to pass on the info that it needs "X" as the device or maybe something else, I am not overly knowledgeable when it comes to this kind of booting process. Hoping you can see whats the matter?
Also I was wondering a decent way to reauthor the iso nicely with ammended boot image data??



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post Jun 11 2010, 01:16 AM
Post #14
Sha0
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Very nice work. smile.gif You are nearly there, indeed. You need to adjust your CONFIG.SYS line for ElTorito.sys to have /d:cd0 at the end. Also, put REM before the oakcdrom line, so that DOS driver will not also try to setup the device-name cd0. If you do all of this and still cannot access drive X:, let us know. smile.gif

The ElTorito.sys DOS driver is typically used to provide the booted-from CD/DVD as a device. The best way to use it is likely:
  • Re-master the .ISO as a no-emulation mode bootable disc, booting to ISOLINUX (or GRUB4DOS, if you like)
  • In your ISOLINUX.CFG file, include an entry for booting the floppy image you've managed to extract (see below)
  • Then use your GRUB4DOS to map and boot the .ISO, forgetting about using the floppy image in GRUB4DOS

The boot sequence will look like: BIOS -> whatever -> GRUB4DOS -> map and boot .ISO -> ISOLINUX -> MEMDISK -> floppy image. Then the ElTorito.sys will find the disc provided by GRUB4DOS. Historically, when using a floppy-emulation CD/DVD, the ElTorito.sys file would only be able to access the portion of the disc containing the floppy-emulation image, which means the rest of the disc's data is inaccessible, and not what you (or most anybody) would want. That's if my memory's working.
ISOLINUX.CFG:
CODE
DEFAULT ghost
LABEL ghost
  KERNEL memdisk
  INITRD ghost.vfd
  APPEND floppy

Re-mastering the .ISO, assuming contents are in isodir\ and ISOLINUX, its config-file, MEMDISK, and the floppy image are in isodir\isolinux\:
CODE
mkisofs -o ghost.iso -b isolinux/isolinux.bin -c isolinux/boot.cat -no-emul-boot -boot-load-size 4 -boot-info-table isodir
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post Jun 11 2010, 03:28 AM
Post #15
tinybit
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(0xff) for eltorito.sys

Many, many BIOSes have a bug that causes eltorito.sys to fail.

This bug was intentional, IMHO. That is to say, they aimed to kick out eltorito.sys. (Oh! Don't ask me why. You should ask yourself, or ask the manufacturers.)

The BIOS creates a faked cdrom drive at DL=0xFF, and then eltorito.sys will fail to find the real drive number, that is, any number ranging from 0x80 to 0xFE.

So, if you use (hd32), which is equivalent to (0xA0), then the eltorito.sys could fail.

You have to use (0xff) for eltorito.sys to work normally:

CODE
map /dos.vfd (fd0)
map /SR3_1_Thin_image.iso (0xFF)
map --hook
root (fd0)
chainloader /io.sys
boot

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post Jun 11 2010, 03:37 AM
Post #16
Sha0
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What is the nature of the failure when probing drive 0xFF on these BIOSes? Perhaps we can fix it in ElTorito.sys. I wonder if that explains this person's problem[1], since MDISKCHK.COM probes all drives by default, too.

[1] issues with mdiskchk.com
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post Jun 11 2010, 03:57 AM
Post #17
tinybit
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Certainly you can fix it. But before doing that, you should test the case in a buggy DELL machine or in any other machine that has the same problem. That kind of machine is easy to find out, because they are plenty.

The buggy BIOS return some info when you call int13/AX=0x4B01/DL=0xFF. Though this info is not of a valid cdrom, but it is sufficient to deceive eltorito.sys and let eltorito.sys think of (0xff) as a valid cdrom.

On the other hand, you cannot simply skip the probing on (0xff), because there are machines that uses (0xFF) for the no-emulation-mode cdrom drive number.
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post Jun 11 2010, 04:19 AM
Post #18
Sha0
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Great info, tinybit. Thanks.

H. Peter Anvin suggested that BIOSes might not check the high bit of DL and might be interpreting a probe at 0xFF as 0x7F which, according to the El Torito specification, means "terminate all" for the AH==0x4B case.

So here[1] is an ElTorito.Sys that counts upwards. If anyone with such a known-buggy BIOS could test, it would be appreciated.

[1] http://www.etherboot.org/share/sha0/eltorito.sys
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post Jun 11 2010, 04:24 AM
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H. Peter Anvin
  
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The other thing to see is if we can put a better filter on the sanity of the response.

sha0 and I talked about how to make sure ISOLINUX falls into this, but it has the benefit of knowing its own boot device.
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post Jun 11 2010, 06:52 AM
Post #20
Technotika
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Well thanks you sha0 and others, we have a break through!!!!! In virtual tests the CD drive is accessed and goes through as expected.
All I need to do now to try for real on the PC's at work, for anyone following and also interested here are the current key aspects of this project

1. grub for dos entry
(will be made even simpler by rebuilding iso with boot floppy info incorporated into the iso just can just have an iso booter!!)

title test 4
map /dos.vfd (fd0)
map /SR3_1_Thin_image.iso (0xFF) nice work tinyb! heh.gif
map --hook
root (fd0)
chainloader /io.sys
boot

2. Config sys entry ( I was worried the auto exec might needed changing from reading other posts but it was only the config.sys needing a couple of bits of tweakage)


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3. Tadaaaaaaaaaaaaa
I should be quickly be able to rustle up the project with the other iso's (similar) I may be back with more troubles but thanks again for helping me achieve what I and others deemed as nigh on impossible. Wahooo yahoo.gif



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