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Booting an ISO image from a DOS FDD without re-boot


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#1 sambul61

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Posted 26 November 2010 - 10:48 PM

OK guys! Now some are familiar with my small project of manipulating file images after booting to a DOS FDD. Quite a few of my questions remain unanswered though.

I know one way to boot another image or drive would be to make a bootable with Grub4DOS floppy, and place a series of menu items in its G4Dos menu.lst. Once you booted the floppy, you can select another image from that menu to boot to.

But what if I need to get out of that G4dos menu, and start working with other programs on that floppy - how to do that?

And once I finished working with the FDD, can I come back to G4dos menu or its command prompt, and then boot another image, CD or HDD from it - how exactly? Or come back and map & hook extra images I want to mount as drives with ELTorito driver after booting to the next image?

#2 Wonko the Sane

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Posted 27 November 2010 - 09:32 AM

As long as we are talking of DOS/Freedos, you can run grub.exe to get back to grub4dos.

Mind you that grub4dos is "sensible" to TSR's and, generally speaking, FreeDOS is a bit "sensible", so your mileage may vary.

Typical:
  • boot (through grldr) to grub4dos
  • do whatever you need to do with mapping/unmapping
  • chainload a DOS
  • do whatever you need to to in DOS
  • run grub.exe
  • you have looped back to #2


:)
Wonko

#3 sambul61

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Posted 27 November 2010 - 03:03 PM

Thanks a lot!

Will try that route and get back on what transpired. I assume, the same is true for booting Windows images as well? You boot to it, then exit from Grub4DOS (HOW exactly?), than go back to Grub4DOS by running grub.exe when required to boot the next image?

Edited by sambul61, 27 November 2010 - 03:05 PM.


#4 Wonko the Sane

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Posted 27 November 2010 - 06:35 PM

I assume, the same is true for booting Windows images as well? You boot to it, then exit from Grub4DOS (HOW exactly?), than go back to Grub4DOS by running grub.exe when required to boot the next image?


DO NOT assume. :)

Rather READ, then THINK. :)


Wonder why I wrote:

As long as we are talking of DOS/Freedos, you can run grub.exe to get back to grub4dos.


:)

Answer these questions:
  • does grub4dos operate in Real Mode or Protected Mode?
  • does DOS operate in Real Mode or Protected Mode?
  • does Windows (BTW WHICH "Windows"?) operate in Real Mode or Protected Mode?

:)
Wonko

#5 sambul61

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Posted 27 November 2010 - 09:11 PM

I'm talking about XP and Win 7 up... They operate in protective mode, and DOS in real mode. Now I guess the time is right to answer my question...with workaround. :)

#6 Wonko the Sane

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Posted 27 November 2010 - 09:22 PM

I'm talking about XP and Win 7 up... They operate in protective mode, and DOS in real mode. Now I guess the time is right to answer my question...with workaround. :)

NO YOU ARE NOT, or, IF YOU ARE, YOU ARE IN THE WRONG PLACE.
This is FreeDOS and DOS.

However:
  • NO workaround available AFAIK.
  • Once you are in Protected Mode, you CANNOT switch to Real Mode.
  • You need to reboot.

:)
Wonko

#7 Sha0

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Posted 28 November 2010 - 05:53 PM

...

  • ...
  • Once you are in Protected Mode, you CANNOT switch to Real Mode.
  • You need to reboot.

That's a slight co-incidence, speaking of the WinKexec thread. Unfortunately, the keyboard seems broken after such a kexec, and will freeze the computer. I wonder if anyone might test a DOS floppy which has MSDOS.SYS configured to lock out the keyboard for FX keys, and with an AUTOEXEC.BAT which displays some output. That might be interesting to see if it runs, but still not totally useful without a keyboard, perhaps.

#8 sambul61

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Posted 28 November 2010 - 07:03 PM

As long as we are talking of DOS/Freedos, you can run grub.exe to get back to grub4dos.

Mind you that grub4dos is "sensible" to TSR's and, generally speaking, FreeDOS is a bit "sensible", so your mileage may vary.

Typical:

  • boot (through grldr) to grub4dos
  • do whatever you need to do with mapping/unmapping
  • chainload a DOS
  • do whatever you need to to in DOS
  • run grub.exe
  • you have looped back to #2

:D
Wonko


But that's equivalent to booting again to the same FDD image (chainload /kernel.sys). Can I get out of Grub4DOS without rebooting the same FDD image, since its already booted and content available during the same "session"? Can calling kernel 2-nd time not result in the FDD reboot but just exiting Grub4DOS - how?

Edited by sambul61, 28 November 2010 - 07:04 PM.


#9 Sha0

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Posted 28 November 2010 - 07:18 PM

But that's equivalent to booting again to the same FDD image (chainload /kernel.sys). Can I get out of Grub4DOS without rebooting the same FDD image, since its already booted and content available during the same "session"? Can calling kernel 2-nd time not result in the FDD reboot but just exiting Grub4DOS - how?

He said you can do whatever you want with mapping and unmapping. Why do you say that's equivalent to booting the same FD image?

#10 sambul61

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Posted 28 November 2010 - 07:21 PM

I appreciate your mediation effort, but a direct suggestion on how to exit Grub4DOS without reboot to the OS you already booted earlier to and called Grub.exe from would be more appropriate, I think. :D

Edited by sambul61, 28 November 2010 - 07:23 PM.


#11 Sha0

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Posted 28 November 2010 - 07:41 PM

I appreciate your mediation effort, but a direct suggestion on how to exit Grub4DOS without reboot to the OS you already booted earlier to and called Grub.exe from would be more appropriate, I think. :D

No, it's not a mediation effort. No, I won't suggest anything until I understand what you want. That's why I included a question in the last post.

Now you've stated that you want to exit GRUB4DOS without a reboot. Use quit to exit GRUB4DOS.




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