Re: Re: [gentoo-user] /dev/sda* missing at boot

Re: Re: [gentoo-user] /dev/sda* missing at boot

[frares]

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Em 18/08/2011 23:27, Mark Knecht <markknecht@gmail.com> escreveu:
> On Thu, Aug 18, 2011 at 11:59 AM, frares@gmail.com> wrote:
> > Hi, guys
> >
> > It is a shame, I know, but after several years using Gentoo, it is the  
> first
> > time I try to build a kernel without "genkernel".
> >
> > And now I can't boot to that new kernel, it does not find (and really  
> do not
> > have a) /dev/sda* root partition ("real-root"); during the boot it  
> stops,
> > complaining about that, gives me the option to get a shell, from which  
> I am
> > able to see that there is no /dev/sda* .
> >
> > I have included everything SATA, so it looks like that is not a kernel
> > problem, but a initramfs issue, I guess.
> >
> > What am I missing?
> >
> > Thanks a lot
> > Francisco
> >
> > PS: my boot partition is sda2, sda3 is a swap partition, and everything
> > else is in sda4. sda1 is not used (up to now) and this is my grub.conf :
> >
> > title Gentoo Linux 2.6.39-gentoo-r3
> > root (hd0,1)
> > kernel /boot/kernel-genkernel-x86_64-2.6.39-gentoo-r3 ro root=/dev/ram0
> > init=/linuxrc real_root=/dev/sda4 vga=0x318 video=uvesafb:1024x768-32
> > nodevfs udev devfs=nomount quiet CONSOLE=/dev/tty1
> > initrd /boot/initramfs-genkernel-x86_64-2.6.39-gentoo-r3

> Maybe I'm missing the obvious here but have you taken a copy of
> whatever config file was used/generated by genkernel and used that as
> a jumping off point for building your own kernel. kernel's a kernel's
> a kernel. What it is capable of doing is in the .config file. If
> genkernel doesn't give you a .config file - I've never used genkernel
> so I don't know what it does - then assuming you have the feature
> turned on you can get the running config using zcat /proc/config.gz.
> Save that to a new .config file, put it in the kernel source directory
> and you should be good to go.

> You can also use zcat /proc/config.gz on the install CD kernel if yuo
> boot from that. Save it to a disk and use it as the basis for creating
> your own config.

> HTH,
> Mark



That's what I am doing right now. I am using genkernel to have something to  
boot on. Then I will try to find a way to optimize another one.

Thanks
Francisco

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Re: [gentoo-user] /dev/sda* missing at boot

[Alan McKinnon]

On Fri 19 August 2011 13:12:25 frares@gmail.com did opine thusly:
> I the case I don't need a initram, I guess that the grub line for
> parameter   passing to the kernel would be empty. Am I wrong?

Yes.

Using or not using kernel parameters has nothing to do with whether 
you use an initramfs or not.

It's the initrd line in grub you do not need.

> 
> I was just looking on how to build my own initram. What is it
> supposed to   do anyway?

First, it's initramfs (the previous incarnation was initrd). You 
should use the correct name.

An initramfs is a filesystems image stored on disk in a place that 
grub can find. It contains a kernel, essential drivers and other bits 
and pieces. When booting, grub finds the image, bangs it into memory 
and instructs the cpu to start executing at a known point.

Why is this useful?

For Gentoo it usually isn't (there are times when it is - see below). 
Binary distros like Ubuntu and Fedora absolutely require this. These 
distros do not know what hardware you have and what drivers you 
require, so they supply drivers for everything. But Ubuntu cannot 
possibly compile into the kernel every possible driver you might need 
to boot as the list would be huge (every known floppy, CD, USB, every 
known MFM, IDE, SATA, SCSI, netboot, Fibre and more driver for a 
start), so what they do instead is probe the hardware at boot time, 
find out what you have, and load the driver modules you DO need.

This is the problem. The kernel wants to load disk drivers so that it 
can access the disk and continue booting. Where are the drivers? Well, 
they are on the disk. Oops, circular problem.

The difficulty is not finding and loading drivers, it's how do you get 
the disk driver off the disk before you have the disk driver in 
memory? (think chicken and egg here).

An initramfs solves this nicely. Grub shoved a disk image into memory 
when it booted. The kernel knows how to access it's memory it doesn't 
need a driver for that. And now the files containing the needed 
drivers are on a virtual disk *in memory*. The kernel loads them, and 
can now access the real physical disks.

Lots more complicated stuff then happens, like getting rid of the 
virtual filesystem from the initramfs and mounting the real filesystem 
from disk at /, but that's beyond the scope of this mail.

Gentoo mostly doesn't need any of this because you do know your 
hardware and can just compile your disk drivers into the kernel - this 
is the very thing that Ubuntu cannot do.

Some Gentoo users still need an initramfs, such as booting off drives 
in a RAID configuration. They need the RAID drivers first to read the 
disks so use an initramfs to fix this little problem exactly as Ubunut 
fixes their problem.

Make sense?


-- 
alan dot mckinnon at gmail dot com

Re: Re: [gentoo-user] /dev/sda* missing at boot

[frares]

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Em 19/08/2011 10:48, Alan McKinnon <alan.mckinnon@gmail.com> escreveu:
> On Fri 19 August 2011 13:12:25 frares@gmail.com did opine thusly:

> > I the case I don't need a initram, I guess that the grub line for
> > parameter passing to the kernel would be empty. Am I wrong?

> Yes.

> Using or not using kernel parameters has nothing to do with whether
> you use an initramfs or not.

> It's the initrd line in grub you do not need.

> >
> > I was just looking on how to build my own initram. What is it
> > supposed to do anyway?

> First, it's initramfs (the previous incarnation was initrd). You
> should use the correct name.

> An initramfs is a filesystems image stored on disk in a place that
> grub can find. It contains a kernel, essential drivers and other bits
> and pieces. When booting, grub finds the image, bangs it into memory
> and instructs the cpu to start executing at a known point.

> Why is this useful?

> For Gentoo it usually isn't (there are times when it is - see below).
> Binary distros like Ubuntu and Fedora absolutely require this. These
> distros do not know what hardware you have and what drivers you
> require, so they supply drivers for everything. But Ubuntu cannot
> possibly compile into the kernel every possible driver you might need
> to boot as the list would be huge (every known floppy, CD, USB, every
> known MFM, IDE, SATA, SCSI, netboot, Fibre and more driver for a
> start), so what they do instead is probe the hardware at boot time,
> find out what you have, and load the driver modules you DO need.

> This is the problem. The kernel wants to load disk drivers so that it
> can access the disk and continue booting. Where are the drivers? Well,
> they are on the disk. Oops, circular problem.

> The difficulty is not finding and loading drivers, it's how do you get
> the disk driver off the disk before you have the disk driver in
> memory? (think chicken and egg here).

> An initramfs solves this nicely. Grub shoved a disk image into memory
> when it booted. The kernel knows how to access it's memory it doesn't
> need a driver for that. And now the files containing the needed
> drivers are on a virtual disk *in memory*. The kernel loads them, and
> can now access the real physical disks.

> Lots more complicated stuff then happens, like getting rid of the
> virtual filesystem from the initramfs and mounting the real filesystem
> from disk at /, but that's beyond the scope of this mail.

> Gentoo mostly doesn't need any of this because you do know your
> hardware and can just compile your disk drivers into the kernel - this
> is the very thing that Ubuntu cannot do.

> Some Gentoo users still need an initramfs, such as booting off drives
> in a RAID configuration. They need the RAID drivers first to read the
> disks so use an initramfs to fix this little problem exactly as Ubunut
> fixes their problem.

> Make sense?


Completely! Thanks a lot.

So I guess that my problem is to find an appropriate pair of driver and  
hard disk operating mode.

> --
> alan dot mckinnon at gmail dot com


Thanks again
Francisco

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Re: [gentoo-user] /dev/sda* missing at boot

[Mick]

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On Friday 19 Aug 2011 03:27:23 Mark Knecht wrote:
> On Thu, Aug 18, 2011 at 11:59 AM,  <frares@gmail.com> wrote:
> > Hi, guys
> > 
> > It is a shame, I know, but after several years using Gentoo, it is the
> > first time I try to build a kernel without "genkernel".
> > 
> > And now I can't boot to that new kernel, it does not find (and really do
> > not have a) /dev/sda* root partition ("real-root"); during the boot it
> > stops, complaining about that, gives me the option to get a shell, from
> > which I am able to see that there is no /dev/sda* .
> > 
> > I have included everything SATA, so it looks like that is not a kernel
> > problem, but a initramfs issue, I guess.
> > 
> > What am I missing?
> > 
> > Thanks a lot
> > Francisco
> > 
> > P.S.: my boot partition is sda2, sda3 is a swap partition, and everything
> > else is in sda4. sda1 is not used (up to now) and this is my grub.conf :
> > 
> > title Gentoo Linux 2.6.39-gentoo-r3
> > root (hd0,1)
> > kernel /boot/kernel-genkernel-x86_64-2.6.39-gentoo-r3 ro root=/dev/ram0
> > init=/linuxrc real_root=/dev/sda4 vga=0x318 video=uvesafb:1024x768-32
> > nodevfs udev devfs=nomount quiet CONSOLE=/dev/tty1
> > initrd /boot/initramfs-genkernel-x86_64-2.6.39-gentoo-r3
> 
> Maybe I'm missing the obvious here but have you taken a copy of
> whatever config file was used/generated by genkernel and used that as
> a jumping off point for building your own kernel. kernel's a kernel's
> a kernel. What it is capable of doing is in the .config file. If
> genkernel doesn't give you a .config file - I've never used genkernel
> so I don't know what it does - then assuming you have the feature
> turned on you can get the running config using zcat /proc/config.gz.
> Save that to a new .config file, put it in the kernel source directory
> and you should be good to go.
> 
> You can also use zcat /proc/config.gz on the install CD kernel if yuo
> boot from that. Save it to a disk and use it as the basis for creating
> your own config.

If you no longer use genkernel it is likely that you do not need an initram.  
Build chipset and fs modules into the kernel.  Other drivers you can choose if 
you want to build as modules. 

-- 
Regards,
Mick

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Re: Re: [gentoo-user] /dev/sda* missing at boot

[frares]

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Em 19/08/2011 07:09, Mick <michaelkintzios@gmail.com> escreveu:
> On Friday 19 Aug 2011 03:27:23 Mark Knecht wrote:
> > On Thu, Aug 18, 2011 at 11:59 AM, frares@gmail.com> wrote:
> > > Hi, guys
> > >
> > > It is a shame, I know, but after several years using Gentoo, it is the
> > > first time I try to build a kernel without "genkernel".
> > >
> > > And now I can't boot to that new kernel, it does not find (and really  
> do
> > > not have a) /dev/sda* root partition ("real-root"); during the boot it
> > > stops, complaining about that, gives me the option to get a shell,  
> from
> > > which I am able to see that there is no /dev/sda* .
> > >
> > > I have included everything SATA, so it looks like that is not a kernel
> > > problem, but a initramfs issue, I guess.
> > >
> > > What am I missing?
> > >
> > > Thanks a lot
> > > Francisco
> > >
> > > PS: my boot partition is sda2, sda3 is a swap partition, and  
> everything
> > > else is in sda4. sda1 is not used (up to now) and this is my  
> grub.conf :
> > >
> > > title Gentoo Linux 2.6.39-gentoo-r3
> > > root (hd0,1)
> > > kernel /boot/kernel-genkernel-x86_64-2.6.39-gentoo-r3 ro  
> root=/dev/ram0
> > > init=/linuxrc real_root=/dev/sda4 vga=0x318 video=uvesafb:1024x768-32
> > > nodevfs udev devfs=nomount quiet CONSOLE=/dev/tty1
> > > initrd /boot/initramfs-genkernel-x86_64-2.6.39-gentoo-r3
> >
> > Maybe I'm missing the obvious here but have you taken a copy of
> > whatever config file was used/generated by genkernel and used that as
> > a jumping off point for building your own kernel. kernel's a kernel's
> > a kernel. What it is capable of doing is in the .config file. If
> > genkernel doesn't give you a .config file - I've never used genkernel
> > so I don't know what it does - then assuming you have the feature
> > turned on you can get the running config using zcat /proc/config.gz.
> > Save that to a new .config file, put it in the kernel source directory
> > and you should be good to go.
> >
> > You can also use zcat /proc/config.gz on the install CD kernel if yuo
> > boot from that. Save it to a disk and use it as the basis for creating
> > your own config.

> If you no longer use genkernel it is likely that you do not need an  
> initram.
> Build chipset and fs modules into the kernel. Other drivers you can  
> choose if
> you want to build as modules.

> --
> Regards,
> Mick


I the case I don't need a initram, I guess that the grub line for parameter  
passing to the kernel would be empty. Am I wrong?

I was just looking on how to build my own initram. What is it supposed to  
do anyway?

Thanks
Francisco

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Re: Re: [gentoo-user] /dev/sda* missing at boot

[Gregory Woodbury]

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On Fri, Aug 19, 2011 at 9:12 AM, <frares@gmail.com> wrote:

> Em 19/08/2011 07:09, Mick <michaelkintzios@gmail.com> escreveu:
> > On Friday 19 Aug 2011 03:27:23 Mark Knecht wrote:
>
> > > On Thu, Aug 18, 2011 at 11:59 AM,  frares@gmail.com> wrote:
> > > > Hi, guys
> > > >
> > > > It is a shame, I know, but after several years using Gentoo, it is
> the
> > > > first time I try to build a kernel without "genkernel".
> > > >
> > > > And now I can't boot to that new kernel, it does not find (and really
> do
> > > > not have a) /dev/sda* root partition ("real-root"); during the boot
> it
> > > > stops, complaining about that, gives me the option to get a shell,
> from
> > > > which I am able to see that there is no /dev/sda* .
> > > >
> > > > I have included everything SATA, so it looks like that is not a
> kernel
> > > > problem, but a initramfs issue, I guess.
> > > >
> > > > What am I missing?
> > > >
> > > > Thanks a lot
> > > > Francisco
> > > >
> > > > P.S.: my boot partition is sda2, sda3 is a swap partition, and
> everything
> > > > else is in sda4. sda1 is not used (up to now) and this is my
> grub.conf :
> > > >
> > > > title Gentoo Linux 2.6.39-gentoo-r3
> > > > root (hd0,1)
> > > > kernel /boot/kernel-genkernel-x86_64-2.6.39-gentoo-r3 ro
> root=/dev/ram0
> > > > init=/linuxrc real_root=/dev/sda4 vga=0x318 video=uvesafb:1024x768-32
> > > > nodevfs udev devfs=nomount quiet CONSOLE=/dev/tty1
> > > > initrd /boot/initramfs-genkernel-x86_64-2.6.39-gentoo-r3
> > >
> > > Maybe I'm missing the obvious here but have you taken a copy of
> > > whatever config file was used/generated by genkernel and used that as
> > > a jumping off point for building your own kernel. kernel's a kernel's
> > > a kernel. What it is capable of doing is in the .config file. If
> > > genkernel doesn't give you a .config file - I've never used genkernel
> > > so I don't know what it does - then assuming you have the feature
> > > turned on you can get the running config using zcat /proc/config.gz.
> > > Save that to a new .config file, put it in the kernel source directory
> > > and you should be good to go.
> > >
> > > You can also use zcat /proc/config.gz on the install CD kernel if yuo
> > > boot from that. Save it to a disk and use it as the basis for creating
> > > your own config.
> >
> > If you no longer use genkernel it is likely that you do not need an
> initram.
> > Build chipset and fs modules into the kernel.  Other drivers you can
> choose if
> > you want to build as modules.
>
> I the case I don't need a initram, I guess that the grub line for parameter
> passing to the kernel would be empty. Am I wrong?
>
> I was just looking on how to build my own initram. What is it supposed to
> do anyway?
>

The initramfs is a container for modules and stuff need to bring up the
system before the mounts of
/ and /boot.    If all the drivers are built-in to the kernel (or at least
the minimum required drivers are built-in)
then the initramfs isn't necessary.

Passing parameters to the kernel is a different issue entirely.

My grub.conf line is:

                kernel /vmlinuz-3.0.3-gentoo root=/dev/sda2
pata_it821x.noraid=1

with the pata_it821x driver built-in for the kenel to find a set of older
IDE drives on the IT8212 card I have installed.

IIRC the initramfs is built with the mkinitrd command.  I haven't had to use
it so I could be wrong.

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Re: Re: [gentoo-user] /dev/sda* missing at boot

[frares]

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Em 18/08/2011 16:13, Michael Mol <mikemol@gmail.com> escreveu:
> On Thu, Aug 18, 2011 at 2:59 PM, frares@gmail.com> wrote:
> >
> > Hi, guys
> >
> > It is a shame, I know, but after several years using Gentoo, it is the  
> first time I try to build a kernel without "genkernel".
> >
> > And now I can't boot to that new kernel, it does not find (and really  
> do not have a) /dev/sda* root partition ("real-root"); during the boot it  
> stops, complaining about that, gives me the option to get a shell, from  
> which I am able to see that there is no /dev/sda* .
> >
> > I have included everything SATA, so it looks like that is not a kernel  
> problem, but a initramfs issue, I guess.

> If you've got a SATA controller, no frills, then all you *really* need
> is AHCI. Build that into your kernel if you're worried about having
> the right modules in initramfs. You can break it out into a module
> later if you like. Opinions differ as to how much stuff should be
> broken into modules vs being built-in to the kernel. I tend to build
> in everything absolutely needed for boot, myself. Some people build in
> just about everything, and some people build in almost nothing.
> There's no "right" way for every use case.

> Also, check your BIOS to see if it's running your SATA controller in
> some kind of IDE emulation mode. If it is, disable that. (Some
> motherboards let you choose between "IDE" and "RAID", where "RAID" is
> AHCI mode. Others call IDE mode 'legacy', and still others might
> actually call the AHCI mode 'AHCI')

> Motherboards running SATA controllers in IDE emulation mode is an
> incredibly common thing:

> 17:18 beh
> 17:18 hda1 turned into sda1
> 17:19 IRule: Turn SCSI-generic support, or did you
> switch from legacy to AHCI in your BIOS?
> 17:20 shortcircuit: quiet, you

> --

> :wq


Thanks, gonna try it.

Francisco

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Re: Re: [gentoo-user] /dev/sda* missing at boot

[frares]

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Em 18/08/2011 16:08, András Csányi <sayusi.ando@gmail.com> escreveu:
> On 18 August 2011 18:59, frares@gmail.com> wrote:

> > Hi, guys
> >
> > It is a shame, I know, but after several years using Gentoo, it is the  
> first
> > time I try to build a kernel without "genkernel".
> >
> > And now I can't boot to that new kernel, it does not find (and really  
> do not
> > have a) /dev/sda* root partition ("real-root"); during the boot it  
> stops,
> > complaining about that, gives me the option to get a shell, from which  
> I am
> > able to see that there is no /dev/sda* .
> >
> > I have included everything SATA, so it looks like that is not a kernel
> > problem, but a initramfs issue, I guess.
> >
> > What am I missing?


> Why have you choose this way? I mean, non-genkernel way.


> --
> - -
> -- Csanyi Andras (Sayusi Ando) -- http://sayusi.hu --
> http://facebook.com/andras.csanyi
> -- ""Trust in God and keep your gunpowder dry!" - Cromwell



That's recommended in the new install manual:

http://www.gentoo.org/doc/en/handbook/handbook-amd64.xml?style=printable&full=1#book_part1_chap7

Look for item "7c". The alternative way is to use genkernel.

Francisco

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