Bootable USB drive

[vkarthik]

I have a 75 GB USB drive that is NTFS formatted (can't use FAT or FAT32 coz I get a "drive too big" error). I want to be able to install bootsectors on this drive so that I can boot into DOS. I use Win XP. Please give me a clue how this can be done.

I have read enough material on the net, so I know that tools like HP Disk Utility, MKBT etc. can be used. My problem is, when I format the floppy with bootsectors, it defaults to FAT. But I can't use the same format on the USB drive since it only seems to support NTFS. So the tools like MKBT didn't work for me.

Please give me an alternate solution.

[gerbil]

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[vkarthik]

Thanks a lot, it was quite informative .. however there is a few things that I need to focus on, so let me throw some more details.

I'm not doing this for maintaining my home pc. I'm actually developing a utility that'll inject bootsectors into USB drive. Here is what I did -

1) On XP, I formatted a floppy with the "create boot disk" option set. So the floppy is now FAT formatted, contains some files and bootsector, can load DOS if I boot using the floppy disk.

2) I used mkbt tool to extract the bootsector info from this floppy and dumped it into a file.

3) Now I have to inject this bootsector (from the file I just dumped it into) into the thumb drive. Again, mkbt can handle it - provided the thumb drive has the same file format (FAT).

So now, to test if this really works, I have to FAT format the usb drive. As I said earlier, I'm unable to do it coz its too big in size and only NTFS seems to be supported.

From what you say, I'm wondering if I could try partitioning the thumb drive, and make one partition small enough to FAT format it (??), and then run mkbt on that partition. Let me know if that'll work, and if so, could you suggest a software that'll create such partitions (or can it be done using windows?)

I might sound dumb, but thats bcoz I am dumb :cheesy:.. well at least with all this disk level stuff .. just started learning, you see.

[gerbil]

oops, i pulled it cos after i posted i saw that u were talking USB. Well, i spose it holds germs of usefulness, so i'll put it back....

[gerbil]

can i clarify something here? what exactly do you wish to put on this USB bootable device? DOS? ie MSDOS, which runs command.com, or cmd.exe, which is what runs in the command window in XP if you type cmd and OK in the run window?

[vkarthik]

well the idea is this ... in case of an OS crash, i need to be able to boot through the usb stick, so that i can run an application that fetches a windows image from elsewhere and re-images the hard drive. normally, doing this with a floppy drive is time-tested. you can just format the floppy as bootable, then load the "utility" i want on the floppy, then boot thru the floppy. after that i can execute the utility and assume that it'll do the rest.

the trouble is, i want to do the same thing with usb stick. im not particular about MS DOS, but im particular about being able to "create" this bootable drive programmatically, without user intervention. in other words, suppose the user plugs in his usb stick when the system is running fine, a program should automatically be able to make the usb stick bootable, and copy my utility on the stick. now when there is a problem with the OS, the user should be able to insert the usb stick and boot thru it (ofcourse, after configuring the bios to boot from this)

hope thats clear.

[gerbil]

well, yeah, a floppy will be FAT.
Lots of stuff to comment on here.
First off, you can put more than one partition on a disk, and you can mix the formats on it to have both NTFS and FAT32, or have several of either all FAT32 or all NTFS. Or FAT if you wish to have MSDOS.
You are using XP, and i shall asssume that it will continue to be your main opsys. XP will only let you format up to 32GB as FAT32, but it will read on a partition much larger [depends on your BIOS] - you just gotta set up the partition with other software. Generally though, XP can handle the building of them, within limits.
Bootsectors and stuff. When you set up the partition(s) on the disk a boot sector will be written for each volume; one, and one only, of them must be marked as active, unless this is a slave disk. There will be only one boot sector per volume [or drive, if you wish.. eg d:]. The disk's master boot record will be written at the same time. Only one of these per disk.
Now I may be way off beam here, explaining what you don't wish to know, but i'll continue.
Windows expects/demands to be on the first partition on the master [hence usually found in c:, or g: if you name it that...]
Startup. BIOS whirs, searches for the master boot record on the master disk. The MBR's partition table for the whole disk is read [the single, active partition is noted], plus the mbr code, and BIOS hands control to that. The code directs operations to the partition marked as active, specifically to its boot sector. That particular boot sector's code assumes control and searches for certain files in the root of the partition. If your OS is XP then ntldr will be read into RAM and then hunt for boot.ini amongst others. Boot.ini will have choices of opsys to load, including your DOS.
The choices you have made available in boot.ini, and the choice you now make, will direct operations toward the OS you wish to run.
== and that is a very brief version of the chain of events!

>>>So. Is it DOS you wish to put down? Then the DOS partition must be a FAT [FAT16] one of max size 2GB. Make your other partitions of sizes you wish, format them with a file system as you wish. Remember, a max of four primary partitions - that is all an MBR can handle.. XP's computer/disk management console will arrange all this. But then you run into a problem... because XP is already on your sys your active boot sector code will be XP and there will not be a DOS copy... so you will need a Boot Manager. [the XP boot sector code will load ntldr which will read boot.ini and display an OS menu - if you choose DOS then ntldr won't work; it is dropped and a DOS boot sector code file is read. But for your way, that file won't exist, so booting will stop right there. You need a Boot Manager.
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Got you. A USB thumb drive it is then, not a 75GB drive. This, then, is where we part, cos I read up on bootable thumb drives a year ago, and there just seemed to be too many uncertainties and incompatibilities. So i stick with my bootable CD and regular system state backups. Have not needed them yet, but you can't make em just when you need em.
But DOS is FAT16, with 2GB max volume size; you should be able to format the pen drive with FAT16, but i think that could also depend on its controller programming... dunno, try it with a 2GB partition. And good luck.

[gerbil]

i changed my earlier post, then saw you were now talking thumbdrives... but decided still to put up my mod post to make the thread sensible.... :)