Bootloader and loadlin

[kalyok]

Hello everyone!

I am a very new person to Linux world and do mainly hardware repairs. I am "Linux challenged", if you will. My problem might look strange and it is not Linux related (it is bootloader related) but I cannot find a complete answer that would satisfy me or prove me wrong. So I will give it a try and ask people here.

One of my instruments I use daily is a small bootable USB stick with various tools such as memtest86, FreeDOS, breakin (advancedclustering.com/software/breakin.html) and DSL. The bootloader on the USB stick is a syslinux. Majority of the tools I use the most live in the DOS image (BIOS updates, various firmware updates, WD/Seagate/Samsung software, hdsdos, etc.). Less often I use breakin and occasionally DSL/memtest.

My main objective is to save time rebooting and having to go through BIOS POST every time I need to switch from DOS to breakin/DSL. Time savings will be significant - some systems are booting to PXE off Intel based NICs and that takes exactly 60 seconds for a NIC to timeout at every boot (not counting the BIOS POST time). There are workarounds but I would love to have it built-in to my USB stick. After weeks of trying to use loadlin to boot breakin from DOS I got nowhere. Recently one of my friend said it will not work since DOS is a 32bit OS and breakin is based on a 64bit OS (I do not know if it is true, but since it supports 32GB + or RAM assume it is).

Loadlin was the only application I know of that would allow DOS to give all the controls to Linux kernel. My question is: do I have any alternatives? Let's look broader - is there a way to boot bootloader from DOS? What about doing the same from Linux? I can boot DSL and from there a script if that would do what I need. Maybe it is possible with some other boot loaders, not syslinux? I understand that the concept of the bootloader is to gain control over system at the system's startup and then pass it on to a selected or default OS. But I still did not give up hope that there is a way to get back to bootloader OR to breakin from DOS without reboot.

Thank you!
-kalyok

[jayd512]

Hello and Welcome!
Just for clarification here.

is there a way to boot bootloader from DOS? What about doing the same from Linux?

Are you meaning that you want to issue a command in the Windows/DOS prompt that will initiate a reboot into Linux?
Or are you looking for a way to use Linux commands, from a repair environment, to manipulate Windows files?

[kalyok]

I want to issue a command in the Windows/DOS prompt that will initiate a reboot into Linux (bootloader, anyone?).

[jayd512]

I might very well be wrong here.

As far as I know, to reboot into Linux, there are only 2 options.

1) Adjust BIOS settings before hand to boot to your rescue medium (USB, LiveCD, etc.)
2) Running a true Windows installation, modifying the boot-loader (a lot of trouble for a rescue medium).

Why not just do what you need to do from the rescue program that you are using? Is rebooting a required step?

[kalyok]

Let me explain my needs in greater details.

Customer's computers may have Linux environment installed, may have Windows installed. It may even be Solaris - I do not care as I am working with hardware only. Sometimes there is no OS installed at all. Whenever we talk about Linux or DOS on this page - it is all on my USB stick, not on any local computer's drive. Whenever I say I need to boot into Linux - it is on my USB drive.

As far as I know, to reboot into Linux, there are only 2 options.

1) Adjust BIOS settings before hand to boot to your rescue medium (USB, LiveCD, etc.)

This step figured out already. I booted the computer off USB drive and choose to boot DOS. Afterward I am working in DOS (doing BIOS upgrade, HDD testing and so on). Once I am done I must run breakin to test every piece of hardware in the computer at once. To do that I need to a) reboot, b) wait for BIOS POST to complete, c) wait for PXE to timeout, and finally d) select breakin from syslinux menu. What I am trying to do is to eliminate steps a) through c) (if it is possible to get to bootloader menu from DOS), or even eliminate steps a) through d) by booting breakin from DOS directly using loadlin (but that never worked).

2) Running a true Windows installation, modifying the boot-loader (a lot of trouble for a rescue medium).

This is not an option - there is no true Windows installation to work with.

Why not just do what you need to do from the rescue program that you are using? Is rebooting a required step?

I cannot do everything from Linux or everything from DOS. Rebooting is not required but booting to both DOS (first) and breakin (Linux based software) is required. So far rebooting is the only way to get from one to another.

That is the whole point that I want to eliminate the reboot!

---------------------

How I tried to run breakin. It consists of two files - kernel and initrd.img. We copy both files along with loadlin.exe into same directory and run the following command:

loadlin kernel root=/dev/ram rw initrd=initrd.img sshpasswd=breakin client=1 startup=breakin vga=1 module_timeout=180

And... it does not work. Probably due to 32/64 bit compatibility issue but I am not an expert to prove that.

So, do you have any ideas how reboot can be eliminated and I can boot linux (breakin) right from DOC prompt? Or maybe there is a way to get to bootloader menu from DOS or Linux prompt?

Thanks,
-kalyok

[kalyok]

You may have a question "why do you need to wait for PXE to timeout". In short - every system I get is set to boot off network first whenever I get to the system and this is the way I need to leave it once system is repaired. It has been proven that it is less time consuming to wait for PXE to timeout twice than to adjust BIOS POST to set USB drive as first boot device and then, after repair is done, to revert settings back.

The main question is not why I have to wait or how to minimize waiting but how I can avoid waiting at all! I know, I want too much

[jayd512]

I do get the point of waiting for the PXE timeout, and I would probably do the same.
But I don't see a way to actually eliminate the need for a reboot.

This is an interesting goal, though. So I'll try to poke around for some ideas.
If you have any other thoughts about it, please post them. We might get lucky and have somebody else chime in.

[yancek]

I'm not really familiar with what you are trying to do but googling loadlin got some sites. Read paragraph 3 in the site below and see if that's close to what you want. You will obviously have to modify it to suit your situation:

Setting up Loadlin

[kalyok]

Thank you yancek for your reply! I have read the article at the link provided and it is not really applicable to my situation. I have FreeDOS OS, not Windows. Pause at boot time will not solve my problem as I must get into DOS, then I need to get out of it and load breakin. Loadlin refuses to work with breakin as apparently breakin uses 64bit Linux image - like I said before, breakin utilizes 95% of RAM (expected percentage) even if 32GB of RAM offered, I do not think 32bit OS can do that. Maybe this is the reason for loadlin not being able to load breakin.

I need to try MS-DOS version of DOS and see if loadlin will load the breakin from there. Also I haven't tried to load DSL or CentOS using loadlin. If I will be able to load these images from FreeDOS it will prove that there are compatibility issues between 32/64 bit OSes. I may not be able to work on this project for next week or so and you may not see my post for next few days as well. Just FYI .

That's about all ideas I've got in regards to loadlin so far. If you have any - please share!

Thanks,
-kalyok

[rcgreen]

I would say that you should keep trying with loadlin. What exactly
does it do when it fails to boot the linux kernel? This is the kind of job
that loadlin was designed for.