This tutorial is currently specific for linux, but for Windows, you only need to change some small things.
I will try to add the Windows parts too, when I have the time.

Download mtools compiled for Windows:
http://ubcdcreator.stopspazzing.com/mto ... 7-win32.7z

mtools manual page:
http://www.gnu.org/software/mtools/manual/mtools.html

Extract /ubcd/images/fdubcd.iso.gz.
Extract fdubcd.img out of the fdubcd.iso.

Make a copy of the existing floppy (just in case you mess up):

Create and format a 2880 kb floppy image and edit the "FDUBCD141" value to the current release version of the FDUBCD image:

If you want a bit more space in your image, you can tweak some FAT parameters:


Download the FreeDOS base iso (fdbasecd.iso) from: http://www.freedos.org/freedos/files/


Open your virtual machine software (qemu, VirtualBox, ..) and attach:

• fdubcd-clean-filesystem.img as floppy image
• fdbasecd.iso as CD image

and boot from CD (FreeDOS):

Qemu:

VirtualBox:
VirtualBox doesn't seem to like to attach 2880 kb floppies, but there is a workaround.

• Move fdubcd-clean-filesystem.img to fdubcd-clean-filesystem-2880.img
• Create a 1440 kb floppy with the same name:
  
  Code:
  mformat -C -f 1440 -v FDUBCD141 -i fdubcd-clean-filesystem.img ::
• Attach this floppy image to VirtualBox
• Close VirtualBox
• Remove the 1440 kb fdubcd-clean-filesystem.img
• Move fdubcd-clean-filesystem-2880.img to fdubcd-clean-filesystem.img
• Start VirtualBOX and see your 2880 kb floppy image attached
• Attach the FreeDOS base ISO (fdbasecd.iso)

In FreeDOS, select "Continue to boot FreeDOS from CD-ROM" (press [ENTER] or type "1" [ENTER])

Then select:


Now we can install the FreeDOS bootsector to our new created floppy image.
Because the FreeDOS CD boots a floppy image with MEMDISK, our attached floppy image is now B: instead of the normal A: drive.

• We install the FreeDOS boot sector code (/OEM:FD)
• And we don't copy the FreeDOS files like KERNEL.SYS at this time (/BOOTONLY)

Now we can close the virtual machine software.


You only need to create the fdubcd-clean-filesystem.img file once. The next time you want to make a modified FDUBCD floppy image, you can start from that image file, copy the needed files inside the image and get a nice fresh floppy image with all files defragmented and with all unused sectors zeroed out (will give a smaller compressed size).

Copy the clean 2880k floppy image with the FreeDOS boot sector installed fdubcd-clean-filesystem.img to a new file on which we can work further (fdubcd-fresh-files.img)

If you started from the fdubcd-clean-filesystem.img file and the FDUBCD version number is updated, you can update the Volume Label with mlabel.

Make a temporary directory (remove the previous one, if it already exists):

Copy the files of the original image (fdubcd-original.img) to the temporary directory:


Change the files you want to change inside the floppy image, by editing the files in the temporary directory.

Sometimes the files in the temporary directory aren't all uppercase, so lets fix this.
FreeDOS can work with them, but it looks nicer if all the filenames look similar.

Convert all lowercase filenames to uppercase:

Copy the files in the temporary directory to our new image (fdubcd-fresh-files.img):

Test your new floppy image in a virtual machine to see if it works:
The FDUBCD image in UBCD is always loaded with MEMDISK, so no changes are written to the fdubcd.img file. Therefore, we load our new image with MEMDISK too, so to test it in a Virtual Machine. Only qemu supports direct booting of MEMDISK (linux kernel format).

Copy your fdubcd-fresh-files.img to fdubcd.img and rebuild the fdubcd.iso.gz image.

With this method, I have now 9 kb more space than in the original FDUBCD141 floppy image (due the parameters given to mformat).

FAT info for the new floppy image created with mformat (custom values):

FAT info for the original floppy image:

FAT info for the new floppy image created with mformat (default values):

_________________
Download Ultimate Boot CD v5.0: http://www.ultimatebootcd.com/download.html
Use Parted Magic for handling all partitioning task: http://partedmagic.com/

There is no need to use the FreeDOS ISO. There is no need to use a temporal folder "/tmp/fdubcd/", and there is no need to "mcopy" twice, using that tmp folder.

Here are my suggestions to change/simplify the procedure.



Not needed. We can use UBCDxxx.ISO instead. I'll use UBCD51a2.ISO in the following procedures.



Use instead:



The last, next step after that one, *was*:

• Attach the FreeDOS base ISO (fdbasecd.iso)

But now I use instead:

• Attach the UBCD ISO (UBCD51a2.iso)

(and use it to boot the VM).

So now you can skip all the FreeDOS instructions. Instead, in UBCD51a2:

• From the Syslinux menu, select FDUBCD DOS and boot into the default booting mode (1).
  
• Once the boot process finishes, select "EXIT" so to go to the DOS prompt.

Then type the following commands:



The last step there (poweroff) should close the VM.



Just to continue with the same names that Icecube used originally:

But now that step is not really necessary. It is only "convenient", so to follow the next steps easily, as Icecube wrote them. I also delete here the rest of the comments around that last copy command.



The next steps are completely unnecessary now.


The next following step is optional, as it was before. It seems this step also changes the "modification date" of the files involved, which IMO is not a desirable change. So I repeat it here to respect the original tutorial, but I do NOT recommend it.



Again, the following steps are not necessary now, since the files are already copied into the new floppy image.

Quote:

Copy the files in the temporary directory to our new image (fdubcd-fresh-files.img):

Code:

mcopy -s -m -p -v -i fdubcd-fresh-files.img /tmp/fdubcd/* ::

The rest are additional steps for building the new fdubcd.ISO and the new modified UBCDxxx.ISO, and for testing it. The new FDUBCD.IMG floppy image was already finished and complete when we ran the "xcopy" command above, so I won't repeat here the same procedures and info.

This simple changes reduces the necessary steps, avoids building a temporary directory and 2 "mcopy" commands. It also avoids downloading and using the "extra" FreeDOS ISO image.

In addition, those steps work under both Linux and Windows, while the original "mcopy" steps have some problems under Windows.

For Windows users, there is an additional/alternative tutorial in the UBCD forum, but using GUI tools. For those interested, it is located at http://www.ultimatebootcd.com/forums/viewtopic.php?p=12188#p12188 with some technical background.