Re: Logical Volume Manager
On Saturday 28 September 2002 6:38 am, Andy Saxena wrote:
> On Thu, Sep 26, 2002 at 08:20:36PM +0100, Alan Chandler wrote:
> > I "think" because I have ext3 as a root partition and am using the debian
> > kernel which has that as a module, debian's installation of the kernel
> > has created an initrd image which it loads on boot and uses to load the
> > ext3 module.
>
> I don't know jack about LVM, but from reading other posts and docs it
> seems that having the root partition on a filesystem that is loaded as a
> module is generally a bad idea. Why don't you compile the ext3 module
> into the kernel? If your root partition is ext3 compiling the driver as
> a module makes little sense as it is going to used all the time.
>
Because I don't need to. Initrd is designed for specifically this sort of
purpose.
The kernel boots the initrd image as a root file system on a ram disk. From
there you load the modules you need, and then with the right modules loaded
you are able to mount the required root file system somewhere else.
The pivot-root command allows you to swap the initrd root with the full root
and get the system going as normal.
Debian does all of this automatically for you when you install one of their
standard kernels and the root file system in not ext2.
There is an issue that I don't understand, and that is why you need the
special "initrd" mechanism in linux at all. I am not sure why you couldn't
boot the kernel with ram disk image using existing mechanisms for specifying
ram disk as root, and then follow what I have just said and issue the pivot
root command to switch to the one you want as the final root.
The issue that concerns me with LVS is is that it has a command to create an
initrd image for booting. I suspect that it is creating something that loads
the lvm modules in the kernel, but the documentation (in your words) contains
"jack shit" about it. What I really need to do is create an initrd image
which loads both lvm AND the ext3 module for root.
Anyway, in the end I just didn't bother. You need a dedicated partition for
/boot to hold the kernel and initrd images anyway, so I was happy to leave 2G
root partition as normal and just use the remaining 86GB of disk space
(spread across 3 disks) as a logical volume.
--
Alan Chandler
alan@chandlerfamily.org.uk
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