Re: root filesystems on a bootable USB CDROM

In article <3caa2818.0306251726.4ea2c0c4@posting.google.com >,
Joe <joe.cooley@lycos.com> wrote:
>Hello,
>
>I am attemting to install a machine that only has a USB CDROM
>attached. I compiled and burned a 2.5.72 kernel image with all the
>necessary drivers. The CD boots fine and asks for a root filesystem
>floppy. I created a root filesystem image on a second CD. At the
>prompt, I replace the kernel image CD with the root filesystem CD.
>The kernel complains that it cannot find the filesystem at sector 0 on
>fd0. I need to somehow get it to look at sr0, the USB CDROM device.
>Does anyone have any idea how to go about this?

It doesn't. That mechanism is solely for a floppy root.

> I tried using rdev to
>change the root device, but that didn't seem to work (could be
>operator error).

Nope. It doesn't work.

> I also tried burning the kernel image and rootfs on
>the same CD, using rdev to provide a rootfs offset to the kernel, but
>that did not seem to work either. I tried using lilo to setup a
>bootdisk by first creating an environment using /dev/ram, copying it
>to a file, and mounting it over /dev/loop, but lilo didn't cooperate.

The tool that you need is the Initial ramdisk, which is designed precisely
for this purpose. The initial ramdisk is a filesystem (which can be compressed)
that is loaded along with the kernel by the bootloader. The kernel will mount
the initrd after booting, and will execute a program/script named linuxrc if
it exists in the root directory of the initrd.

If you want to see all of this in action, simply boot any existing distribution
CDROM. Slackware, RedHat, gentoo, and especially KNOPPIX all use this technique
to get going.

>
>Any documentation pointers and/or ideas would be extremely appreciated
>- I am knee deep in coasters. I have looked into the bootdisk howto
>among others and did not find a suitable solution.

Well my confusion is why you are trying to craft this by hand? If the kernel
recognizes and maps the USB CDROM as /dev/sr0, then any distribution worth
its salt will pick it up upon boot.

The final element that you failed to inform us: what exactly are you trying
to install. That info would be a big help.

BAJ

byron@cc.gatech.edu (Byron A Jeff) wrote in message news:<bdeqgv$6ab@cleon.cc.gatech.edu>...
> In article <3caa2818.0306251726.4ea2c0c4@posting.google.com >,
> Joe <joe.cooley@lycos.com> wrote:
> >Hello,
> >
> >I am attemting to install a machine that only has a USB CDROM
> >attached. I compiled and burned a 2.5.72 kernel image with all the
> >necessary drivers. The CD boots fine and asks for a root filesystem
> >floppy. I created a root filesystem image on a second CD. At the
> >prompt, I replace the kernel image CD with the root filesystem CD.
> >The kernel complains that it cannot find the filesystem at sector 0 on
> >fd0. I need to somehow get it to look at sr0, the USB CDROM device.
> >Does anyone have any idea how to go about this?
>
> It doesn't. That mechanism is solely for a floppy root.
>
> > I tried using rdev to
> >change the root device, but that didn't seem to work (could be
> >operator error).
>
> Nope. It doesn't work.
>
> > I also tried burning the kernel image and rootfs on
> >the same CD, using rdev to provide a rootfs offset to the kernel, but
> >that did not seem to work either. I tried using lilo to setup a
> >bootdisk by first creating an environment using /dev/ram, copying it
> >to a file, and mounting it over /dev/loop, but lilo didn't cooperate.
>
> The tool that you need is the Initial ramdisk, which is designed precisely
> for this purpose. The initial ramdisk is a filesystem (which can be compressed)
> that is loaded along with the kernel by the bootloader. The kernel will mount
> the initrd after booting, and will execute a program/script named linuxrc if
> it exists in the root directory of the initrd.
>
> If you want to see all of this in action, simply boot any existing distribution
> CDROM. Slackware, RedHat, gentoo, and especially KNOPPIX all use this technique
> to get going.
>
> >
> >Any documentation pointers and/or ideas would be extremely appreciated
> >- I am knee deep in coasters. I have looked into the bootdisk howto
> >among others and did not find a suitable solution.
>
> Well my confusion is why you are trying to craft this by hand? If the kernel
> recognizes and maps the USB CDROM as /dev/sr0, then any distribution worth
> its salt will pick it up upon boot.
>
> The final element that you failed to inform us: what exactly are you trying
> to install. That info would be a big help.
>
> BAJ

I need to craft this by hand (using 2.5) because the installation
machine contains a large RAID array with 2 TB of disk space and I
cannot get a normal distribution such as Debian and/or RedHat to
install. The 2.4 limit is 2 TB and some of the distros are limited to
1 TB (ascertained through experimentation).