Re: [SLUG] Copying and booting linux with a partition with a different filesystem type

From: Paul M Foster (
Date: Mon Mar 31 2008 - 16:27:07 EST

On Mon, Mar 31, 2008 at 01:25:49PM -0400, Eben King wrote:

> On Mon, 31 Mar 2008, Paul M Foster wrote:
>> On Sun, Mar 30, 2008 at 11:25:24PM -0400, Eben King wrote:
>>> There's either a kernel flag for it supplied by the bootloader, or the
>>> kernel expects / to be mounted when it's invoked, I can't figure
> out which.
>>> /etc/fstab has an entry for / , but it must be dummy, since by that time
>>> /
>>> is already mounted. The kernel needs support for /'s filesystem, either
>>> modular (and in the initrd) or in the kernel. If the module to access
> / is
>>> on /, you have a nice catch-22.
>> I don't think so. Once configured properly, grub knows how to load your
>> *boot* filesystem. The entry in /etc/fstab takes over, loading the
>> *root* filesystem once grub has loaded the boot filesystem and booted the
>> machine.
> What's in the boot filesystem? I have no initrd, so that isn't necessary.

Well, with grub in particular, there is frequently a subdirectory called
/boot which contains all the files grub needs to boot the system, and
that subdirectory can be its own partition on the hard drive. But either
way, the bootloader boots the boot filesystem first, independently of
whatever else. Once the boot filesystem is loaded, the kernel can be
loaded and take over with the root filesystem. Back in the day, there
used to be a boot floppy and a root floppy for certain distros, because
the bootloader has to get everything ready for the kernel to be able to
read its root filesystem. Put it this way-- if the kernel could boot
itself, there would be no need for lilo or grub. The bootloader has only
enough intelligence to boot the system. Then it transfers control to the


Paul M. Foster
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