[gentoo-user] dual-linuxdistro-boot kernel question

[gentoo-user] dual-linuxdistro-boot kernel question

[Fernando Meira]

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Hi,
I was told the following, which I don't agree, but in any case, I would like 
to hear from someone that knows :)
- when having 2 different distro on 1 pc, do they have to use the same 
kernel?
Even if they share the same swap partition and /boot is inside the root of 
one of the distros (and not in a separate partition)...

Cheers,
Fernando

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Re: [gentoo-user] dual-linuxdistro-boot kernel question

[Luke Albers]

On Tue, 2005-08-16 at 13:12 +0000, Fernando Meira wrote:

> - when having 2 different distro on 1 pc, do they have to use the same
> kernel?


no

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Re: [gentoo-user] dual-linuxdistro-boot kernel question

[Holly Bostick]

Fernando Meira schreef:
> Hi,
> I was told the following, which I don't agree, but in any case, I would
> like to hear from someone that knows :)
> - when having 2 different distro on 1 pc, do they have to use the same
> kernel?
> Even if they share the same swap partition and /boot is inside the root
> of one of the distros (and not in a separate partition)...
> 
> Cheers,
> Fernando

No, they do not-- in fact, I personally think it's weird for them to use
the same kernel (I never heard of doing this before recently).

Just to authenticate myself, I currently run Gentoo and SuSE on the same
PC, and previously ran Gentoo, RedHat9, Morphix, CollegeLinux, and
Mandrake (with Win 98 and Win2K) on the same PC.

Especially when one of the distros in question is a binary distro
(Mandrake, SuSE, RedHat/Fedora, and to some extent, Debian-based
distros, and Gentoo), you wouldn't want them to use the same kernel
anyway, as binary distros are well-known to patch their kernels for the
distribution (as does Gentoo, but the Gentoo patches are not as
'essential' to the kernel's proper running as, say, SuSE's are if you're
running SuSE). Naturally, I wouldn't expect the binary distro's kernel
patches to be compatible with Gentoo, or vice-versa.

Now, of course, you could use a vanilla kernel under both (or all)
relevant distros, but that would probably be a problem for the binary
distro (after all, if the kernel patches weren't necessary, they
wouldn't put all the work in to patch the kernel, would they?).

What I do is *copy* the binary distro's kernel to the /boot partition
(which is a separate mounted partition under Gentoo, but is a folder
under / in SuSE), so that way, both distros can use the kernel they
expect to see, and it all works fine.

Why you'd really want to have two or more distros using the same kernel
at all, I really can't get, but maybe I'm dim :-) .

Holly

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Re: [gentoo-user] dual-linuxdistro-boot kernel question

[Christoph Gysin]

Fernando Meira wrote:
> I was told the following, which I don't agree, but in any case, I would 
> like to hear from someone that knows :)
> - when having 2 different distro on 1 pc, do they have to use the same 
> kernel?
> Even if they share the same swap partition and /boot is inside the root 
> of one of the distros (and not in a separate partition)...

No, they don't have to. But they could ;-)

The bootloader could select the distribution by passing the "root=/dev/hda?" 
boot parameter.

Christoph
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Re: [gentoo-user] dual-linuxdistro-boot kernel question

[Fernando Meira]

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That was exactly what I was thinking... 
My doubt arose when I got the following reply of a dual-boot installation 
with Ubuntu and Gentoo:
"you have to use the same kernel from the Ubuntu installation for Gentoo 
(unless or course you manually upgrade it), however either way you end up 
with vanilla."
Even that this guy/girl has /boot inside Ubuntu's partition, it still needs 
(in case he wants 2 different kernels) to place gentoo's kernel inside /boot 
so that he can start gentoo.

Thanks for the replies.
Fernando.

On 8/16/05, Christoph Gysin <cgysin@gmx.ch> wrote:
> 
> Fernando Meira wrote:
> > I was told the following, which I don't agree, but in any case, I would
> > like to hear from someone that knows :)
> > - when having 2 different distro on 1 pc, do they have to use the same
> > kernel?
> > Even if they share the same swap partition and /boot is inside the root
> > of one of the distros (and not in a separate partition)...
> 
> No, they don't have to. But they could ;-)
> 
> The bootloader could select the distribution by passing the 
> "root=/dev/hda?"
> boot parameter.
> 
> Christoph
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> 
>

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Re: [gentoo-user] dual-linuxdistro-boot kernel question

[Russell Slater]

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Couldn't you place both kernels in /boot with different names and leverage 
grub to load the approriate one?

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Re: [gentoo-user] dual-linuxdistro-boot kernel question

[Holly Bostick]

Russell Slater schreef:
> Couldn't you place both kernels in /boot with different names and
> leverage grub to load the approriate one?

Yes. Afaik, this is the 'traditional' method, both within a single
distro with multiple kernel versions, and with multiple distros that
each have a single kernel.

If you originally set up both distros to point to the same external
partition as /boot, then there is no problem, as the kernels will both
be installed to the same /boot partition, and will most likely have
different names by default.

If, like me, you installed one distro with /boot as just a folder on the
/ partition, then installed the second using a separate partition as
/boot, then you likely have to do what I did and copy one kernel (and
associated files) to the /boot of the distro whose bootloader you're
using, but of course, if you have to do that, you can easily rename the
copied kernel to something unique, if for some reason it isn't already
uniquely named.

Edit your bootloader config, and you're done.

Holly
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Re: [gentoo-user] dual-linuxdistro-boot kernel question

[Neil Bothwick]

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On Tue, 16 Aug 2005 17:12:01 +0200, Holly Bostick wrote:

> If, like me, you installed one distro with /boot as just a folder on the
> / partition, then installed the second using a separate partition as
> /boot, then you likely have to do what I did and copy one kernel (and
> associated files) to the /boot of the distro whose bootloader you're
> using,

You don't have to copy anything, because the kernel doesn't have to be in
the same directory as the bootloader config. It's perfectly acceptable,
and a lot easier to manage, if all your secondary distros have their own
/boot directory, probably not a separate partition.

> but of course, if you have to do that, you can easily rename the
> copied kernel to something unique, if for some reason it isn't already
> uniquely named.


-- 
Neil Bothwick

Committee (noun): A group of people spending hours taking minutes

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Re: [gentoo-user] dual-linuxdistro-boot kernel question

[Holly Bostick]

Neil Bothwick schreef:
> On Tue, 16 Aug 2005 17:12:01 +0200, Holly Bostick wrote:
> 
> 
>>If, like me, you installed one distro with /boot as just a folder on the
>>/ partition, then installed the second using a separate partition as
>>/boot, then you likely have to do what I did and copy one kernel (and
>>associated files) to the /boot of the distro whose bootloader you're
>>using,
> 
> 
> You don't have to copy anything, because the kernel doesn't have to be in
> the same directory as the bootloader config. It's perfectly acceptable,
> and a lot easier to manage, if all your secondary distros have their own
> /boot directory, probably not a separate partition.
> 

Maybe under normal circumstances it is, but SUSE really doesn't seem to
like booting from Gentoo's bootloader when the SUSE kernel is on the
other partition (not in the /boot partition my Gentoo uses). Of course,
the SUSE kernel doesn't like to boot from 'normal' entries, either-- I
recall when I was still using LiLO, that I had to physically copy the
SuSE entry from SuSE's lilo.conf to the lilo.conf I was actually using,
because just adding a standard entry to point to the SuSE
kernel/partition wouldn't boot SuSE.

But it's quite possible that SuSE is the only (or one of the very few)
distros that is that picky. And it's also possible that I did something
wrong so that it seemed that picky, when it really isn't (but I think it
really is :) ).

Holly
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Re: [gentoo-user] dual-linuxdistro-boot kernel question

[Gyuri]

Fernando Meira wrote:

> Hi,
> I was told the following, which I don't agree, but in any case, I 
> would like to hear from someone that knows :)
> - when having 2 different distro on 1 pc, do they have to use the same 
> kernel?
> Even if they share the same swap partition and /boot is inside the 
> root of one of the distros (and not in a separate partition)...
>
> Cheers,
> Fernando

No, but they can use a common kernel, if you want to. The same swap 
space can be used, it's not a question. (If you want to have 2 distros 
on 1 pc, a swap partition is recommended insted of a swap file for each) 
It can happen because at the same time, only one of them can boot up.
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Re: [gentoo-user] dual-linuxdistro-boot kernel question

[Neil Bothwick]

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On Tue, 16 Aug 2005 17:45:37 +0200, Holly Bostick wrote:

> Maybe under normal circumstances it is, but SUSE really doesn't seem to
> like booting from Gentoo's bootloader when the SUSE kernel is on the
> other partition (not in the /boot partition my Gentoo uses). Of course,
> the SUSE kernel doesn't like to boot from 'normal' entries, either-- I
> recall when I was still using LiLO, that I had to physically copy the
> SuSE entry from SuSE's lilo.conf to the lilo.conf I was actually using,
> because just adding a standard entry to point to the SuSE
> kernel/partition wouldn't boot SuSE.

When I was dual-booting Gentoo and SUSE, I let SUSE install its
bootloader onto it's root partition and chainloaded it from Gentoo's
GRUB. It saved any such hassle.


-- 
Neil Bothwick

MIPS: Meaningless Indication of Processor Speed

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Re: [gentoo-user] dual-linuxdistro-boot kernel question

[Holly Bostick]

Neil Bothwick schreef:
> On Tue, 16 Aug 2005 17:45:37 +0200, Holly Bostick wrote:
> 
> 
>>Maybe under normal circumstances it is, but SUSE really doesn't seem to
>>like booting from Gentoo's bootloader when the SUSE kernel is on the
>>other partition (not in the /boot partition my Gentoo uses). Of course,
>>the SUSE kernel doesn't like to boot from 'normal' entries, either-- I
>>recall when I was still using LiLO, that I had to physically copy the
>>SuSE entry from SuSE's lilo.conf to the lilo.conf I was actually using,
>>because just adding a standard entry to point to the SuSE
>>kernel/partition wouldn't boot SuSE.
> 
> 
> When I was dual-booting Gentoo and SUSE, I let SUSE install its
> bootloader onto it's root partition and chainloaded it from Gentoo's
> GRUB. It saved any such hassle.

Ah... *there's* the missing link. Chainloading. One of my blind spots,
meaning that I don't know anything about it except wrt Windows, which
was and is no longer a factor. So I didn't try that wrt SuSE.

Thanks. I learn something new every day around here.

Holly
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