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Bypassing GRUB

Dr. Parthasarathy S [drpartha at gmail.com]


Fri, 10 Dec 2010 19:16:43 +0530

I often experiment with multiple distros (for learning/teaching value), by installing them on my machine side by side. I then get to use a specific distro/kernel by selecting it through GRUB, at boot time. Is there some way to by-pass GRUB altogether and boot a specific kernel manually ?

Let me be clear, I want to bypass GRUB and choose the kernel/distro manually. It is not about replacing the sick GRUB by a healthy GRUB.

I would appreciate any clue or pointer.

Thank you,

partha

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Dr. S. Parthasarathy                    |   mailto:drpartha at gmail.com
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Neil Youngman [ny at youngman.org.uk]


Fri, 10 Dec 2010 14:12:27 +0000

On Friday 10 Dec 2010 13:46:43 Dr. Parthasarathy S wrote:

> I often experiment with multiple distros (for learning/teaching value), by
> installing them on my machine side by side. I then get to use a
> specific distro/kernel by selecting it through GRUB, at boot time. Is there
> some way to by-pass GRUB altogether and boot a specific kernel
> manually ?
> 
> Let me be clear, I want to bypass GRUB and choose the kernel/distro
> manually. It is not about  replacing the sick GRUB by a healthy GRUB.
> 
> I would appreciate any clue or pointer.

I assume by bypassing GRUB, you mean bypassing the GRUB menu. GRUB 0.9 allowed you to press 'c' (IIRC) to get a prompt where you could enter commands including selecting a kernel, setting boot parameters and telling it to boot with whatever settings you have given it. I assume GRUB2 is the same in this respect, but you would need to check that for yourself. I'm sure you can find plenty of information with Google.

HTH

Neil Youngman


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Ben Okopnik [ben at linuxgazette.net]


Mon, 13 Dec 2010 01:28:55 -0500

On Fri, Dec 10, 2010 at 07:16:43PM +0530, Dr. Parthasarathy S wrote:

> I often experiment with multiple distros (for learning/teaching value), by
> installing them on my machine side by side. I then get to use a
> specific distro/kernel by selecting it through GRUB, at boot time. Is there
> some way to by-pass GRUB altogether and boot a specific kernel
> manually ?

Hi, Partha - I'm not very clear on what you're trying to do; it seems to me that you're operating from an incorrect concept. If you have multiple OSes, then you need some sort of a selection mechanism for them.

Given how little data the BIOS can work with, that first stage is pretty tiny; there's really nothing there that's optional, or that can be stripped out. In other words, you can have a single-boot system (MBR in the first sector passing control to the OS-specific boot record elsewhere) or a multi-boot system (IPL and partition table in the first sector, second-stage "boot manager" that grabs the boot data from the bootable partitions and passes control to the one you choose.) As a result, there's no way to "just" boot one of a list of OSes without having everything set up the second way.

-- 
* Ben Okopnik * Editor-in-Chief, Linux Gazette * http://LinuxGazette.NET *


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Dr. Parthasarathy S [drpartha at gmail.com]


Mon, 13 Dec 2010 12:09:48 +0530

I see your point.

Thank you,

partha

On 13/12/2010, Ben Okopnik <ben at linuxgazette.net> wrote:

> On Fri, Dec 10, 2010 at 07:16:43PM +0530, Dr. Parthasarathy S wrote:
>> I often experiment with multiple distros (for learning/teaching value), by
>> installing them on my machine side by side. I then get to use a
>> specific distro/kernel by selecting it through GRUB, at boot time. Is
>> there
>> some way to by-pass GRUB altogether and boot a specific kernel
>> manually ?
>
> Hi, Partha - I'm not very clear on what you're trying to do; it seems to
> me that you're operating from an incorrect concept. If you have multiple
> OSes, then you need some sort of a selection mechanism for them.
>
> Given how little data the BIOS can work with, that first stage is pretty
> tiny; there's really nothing there that's optional, or that can be
> stripped out. In other words, you can have a single-boot system (MBR in
> the first sector passing control to the OS-specific boot record
> elsewhere) or a multi-boot system (IPL and partition table in the first
> sector, second-stage "boot manager" that grabs the boot data from the
> bootable partitions and passes control to the one you choose.) As a
> result, there's no way to "just" boot one of a list of OSes without
> having everything set up the second way.
>
>
> --
> * Ben Okopnik * Editor-in-Chief, Linux Gazette * http://LinuxGazette.NET *
>                                              
> TAG mailing list
> TAG at lists.linuxgazette.net
> http://lists.linuxgazette.net/listinfo.cgi/tag-linuxgazette.net
>
-- 
---------------------------------------------------------------------------------------------
Dr. S. Parthasarathy                    |   mailto:drpartha at gmail.com
Algologic Research & Solutions    |
78 Sancharpuri Colony                 |
Bowenpally  P.O                          |   Phone: + 91 - 40 - 2775 1650
Secunderabad 500 011 - INDIA     |
WWW-URL: http://algolog.tripod.com/nupartha.htm
GPG Public key :: http://algolog.tripod.com/publikey.htm
---------------------------------------------------------------------------------------------


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Raj Shekhar [rajlist2 at rajshekhar.net]


Fri, 07 Jan 2011 17:12:16 -0800

In infinite wisdom Dr. Parthasarathy S said the following On 12/10/10 5:46 AM:

> I often experiment with multiple distros (for learning/teaching value), by
> installing them on my machine side by side. I then get to use a
> specific distro/kernel by selecting it through GRUB, at boot time. Is there
> some way to by-pass GRUB altogether and boot a specific kernel
> manually ?

Ted Dziuba has written steps on using chroots for trying out various distros <http://teddziuba.com/2011/01/multiple-concurrent-linux-distros.html>

If you are picky about "clean" environment, you can think of using virtual machines to try out different distros (my preferred method, because CPU power is so cheap now)


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