On Fri, Feb 18, 2011 at 1:36 PM, Pierre Lorenzon <[email protected] > wrote:
> > Hi Nathan, > > From: Nathan Coulson <[email protected]> > Subject: Re: kernel options > Date: Thu, 17 Feb 2011 16:32:41 -0800 > > > On Wed, Feb 16, 2011 at 12:11 PM, Pierre Lorenzon < > > [email protected]> wrote: > > Thanks for your answer. But I am not sure to completely > understand the situation : Is the root= option on the line > kernel ABSOLUTELY MANDATORY if there's no initrd or initramfs > ? > the default it chooses, is whatever was mounted as / when the kernel was compiled. ex:/ if /dev/sda2 was mounted as /, that's what it uses. [I think this behavior may have been taken out somewhere in the last 10 kernels, as they considered this behavior obsolete. but I can confirm it does not autodetect] you can change this with rlimit, (if that's still around) to another partition (but it's still sd##, or hd##) > > > > > > you may have to resort to building a initrd or a initramfs. Without one, > > you need to specify a partition. > > > > just consider it like a "mini" linux system that can run a small bash > > script, which could find your usb stick, mount it, and continue. there > is a > > command called switch_root that is very useful for this. At that stage > > too, you can use UUID's if you have a linux environment to work with. > > > > Documentation/kernel-parameters.txt in the linux kernel may have other > > I find this documentation very minimal. Indeed I didn't see > any answer to my question above about the fact that an option > SHOULD have a value or might be leaved empty and in which > circumstances. Anyway if you have a good suggestion for a > documentation to learn these things I'd greatly appreciate ! > > > > options that I am unaware of, but afaik, root= can only be given devices. > > > > there was a way to determine what your boot device was in /sys, but I > > believe you still need a initrd/initramfs to take advantage of this. > > This is a paradox indeed ! Information is available in the > kernel since it will be exported to the sys by the kernel > itself (I suspect at leat !) but kernel cannot export this > information to itself ! I know that things might be more > complicated than I simply think, but anyway ... > > Regards > > Pierre > In most cases, they have always preferred to have the logic in a initrd/initramfs, instead of bloating their kernel code. I cannot speak for them though. If the kernel could use the UUID to mount it, that would be the easiest solution (again, another solution you'd have to make a initrd/initramfs for though) > > > > > -- > > Nathan Coulson (conathan) > > ------ > > Location: British Columbia, Canada > > Timezone: PST (-8) > > Webpage: http://www.nathancoulson.com > -- > http://linuxfromscratch.org/mailman/listinfo/blfs-support > FAQ: http://www.linuxfromscratch.org/blfs/faq.html > Unsubscribe: See the above information page > -- Nathan Coulson (conathan) ------ Location: British Columbia, Canada Timezone: PST (-8) Webpage: http://www.nathancoulson.com
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