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Jul. 16, 2018

main | openbsd :: installation :: boot_floppy

Making a Boot Floppy using OpenBSD or Linux

The Installation chapter talks about making a boot floppy using the DOS executable RAWRITE.EXE. Back when we wrote the book, most people were still using Windows, and users of Unix systems were generally familiar enough to create their own floppy from an image.

With the massive growth of linux users, there are now a lot of newbie users that might not yet know the intricacies of the disk-dump program ("dd"). This program dumps the contents of a file to a disk device. It is a raw, low level tool. It doesn't care what the file is or what the device is. It will just take the bytes from the file and shove it out to the device, with various optional formatting.

For our purposes, we will tell the dumper to write the entire floppy image as one big block to the floppy drive. The command to do this is:

dd if=floppy27.fs of=/dev/fd0 bs=1440k count=1

dd if=floppy27.fs of=/dev/fd0a bs=1440k count=1

"if" is Input File, and here we're inputting the floppy27.fs disk image which you hopefully have in the current directory (otherwise give the full path to the image file).

"of" is the Output File, which in this case is our floppy drive, accessible at /dev/fd0 (/dev/floppy sometimes) on many linux distros and /dev/fd0a on standard OpenBSD dist. If neither works for you, hunt around the various docs to locate your floppy device (if you have multiple devices, try fd1, fd0b, fd1a, fd, etc.).

"bs" tells the program to read and write xxx number of bytes at a time. In our case, we're writing 1440K bytes, which is the size of a std. floppy. This will write the whole image file in one shot.

"count" is the number of blocks that the program should write. Since we're writing the whole file in one block, we'll set this to one. In case you're wondering, setting bs to 1K and count to 1440 will probably not work -- blocks are not necessarily contiguous and therefore the image might get broken up and written in the wrong order. I'm not a disk IO guy, but I think this is correct... feel free to correct me if I'm wrong here. Either way, the method which I suggest WILL work properly, so use that!

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