Root on LVM without initrd?

[James Le Cuirot]

Hello,

There seems to be a lot of conflicting information out there about
having your root partition on LVM. My boot partition is not on LVM so I
have no trouble there. I am under the impression that GRUB2's LVM
support means that it is no longer necessary to use an initrd when your
root is on LVM. It creates entries like this...

menuentry 'GNU/Linux, with Linux 3.1.0-gentoo-r1' --class gnu-linux --class gnu 
--class os {
        load_video
        insmod gzio
        insmod part_msdos
        insmod ext2
        set root='(hd1,msdos5)'
        search --no-floppy --fs-uuid --set=root 
ee946103-1b8b-4a1c-8e6a-e272dc823e51
        echo    'Loading Linux 3.1.0-gentoo-r1 ...'
        linux   /vmlinuz-3.1.0-gentoo-r1 root=/dev/mapper/symphony-root ro
}

It loads "insmod lvm" further up and if I type "ls" at the console, I
see that it has recognised my LVM partitions. But when the kernel
actually fires up, I get the "Unable to mount root fs" error. The
kernel does have device mapper support built in. If an initrd really is
needed then why does GRUB generate entries like the above?

Regards,
James