ms-sys vs syslinux
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They will probably both be able to boot a system, but they contain slightly different data as they come from different sources. Those different data will probably only be notable by an end user as slightly different error messages if something goes wrong. The switch -7 writes an MBR which looks as the one from Microsoft Windows 7. It is also possible to write an MBR looking as it came from syslinux with the switch -s, however even that one might differ slightly depending on version of syslinux.
The MBR is the first step to boot, then you will also need a working boot record in the active bootable partition and that boot record might need some file on the filesystem.
I have only just registered and am trying to find some help for creating a DOS bootable device using FreeBSD.
I can compile ms-sys without trouble but cannot manage to create a DOS bootable USB stick.
Any help would be appreciated.
An example would be welcomed.
Sorry, I have no experience from FreeBSD myself. Others have contributed all the code for OpenBSD and FreeBSD.
I can compile it just want to know what options I need to use and how do I check whether it has worked properly.
I could try it on Debian first if I know what I should expect.
What options you need to use completely depends upon what you are going to boot and what you are going to use to boot it. First of all, ms-sys in itself is not capable of creating a "bootable disk", you will need some kind of operating system to boot. Next, ms-sys is only capable of writing the kind of boot records usable by legacy BIOS computers, if your system has UEFI boot only, ms-sys will not be to any use for you.
The initial and still main intention of ms-sys is to be a Linux tool to make legacy Microsoft Windows installations bootable.
What are you trying to do? What did you try? What was the outcome? What outcome did you expect?
Last edit: Henrik Carlqvist 2026-02-10
I want to create a bootable USB stick to perform a BIOS upgrade on a ThinkPad X61.
Sorry, ms-sys is not enough to create a bootable USB stick. To become bootable, you will need to install some kind of operating system on that USB stick. Whatever operating system that you choose will most likely provide you with all tools needed to make it bootable. Ms-sys is only a tool to identify and fix boot records. Once booted, boot records will need something to chain to. The master boot record might need to pass on to a partition boot record (so far ms-sys will be able to provide both for you), but then the partition boot record will need to pass on to something like IO.SYS and MSDOS.SYS.
Do you have contact with these people?
No, I do not have any contact with the people who has contributed code. Most contributors have only added some single feature that they needed for themselves. It is not like we would be some group that continues to work together.
Basically I want something which provides equivalent of DOS FDISK.
I have PC-DOS 7 but only as an ISO. That includes FDISK but I don't have anything to run it from.
Will Ms-sys create a boot record? And if so on what sort of device and how big?
The main purpose of DOS FDISK is to create partitions, ms-sys cannot do that. There are other free tools for that like Linux fdisk, cfdisk parted or gparted.
However, ms-sys is capable of doing the equivalent of DOS "FDISK /mbr", that is writing master boot records. The master boot record consists of the first 512 bytes of a device and only part of those 512 bytes are the code to boot, in the MBR you also have the DOS partition table. Ms-sys does not alter or create the partition table.
The fact that you are asking these questions indicates to me that ms-sys is not a tool I would recommend to you. Passing the wrong arguments to ms-sys can easily wipe all data from some disk that you consider important.
Again, to make something boot you will need an operating system. Whatever operating system you choose will probably give you a more friendly user interface to make it bootable than ms-sys.
If you are unable to burn and boot your ISO from optical media you would probably be able to boot it in some virtual machine like qemu. You could also give your USB device to qemu, so you would probably be able to create a USB stick that is bootable at least in qemu. However, the fact that you have made a USB stick bootable in some real or virtual machine does not mean that it will be bootable in every machine out there. Some machines only want to boot in UEFI mode, some machines are not able to boot from USB at all.