impossible de booter que ce soit lilo ou grub

fstab : # NOTE: If your BOOT partition is ReiserFS, add the notail option to opts.
/dev/sda1		/boot		ext2		noauto,noatime	1 2
/dev/sda2		/		ext3		noatime		0 1
/dev/sda3		/home           ext3            noatime         0 1
/dev/sda5		none		swap		sw		0 1
/dev/sda6               /opt	        ext3            noatime         0 1
/dev/cdroms/cdrom0	/mnt/cdrom	iso9660		noauto,ro	0 0
/dev/fd0		/mnt/floppy	auto		noauto		0 0
#/dev/hdb1		/mnt/hdb1	ext3		noatime		0 0
#/dev/hdc1		/mnt/hdc1       ntfs-3g locale=fr_FR@euro,uid=1000,gid=1003       0 0
#/dev/hdd1		/mnt/hdd1	ext3		defaults	0 0
# NOTE: The next line is critical for boot!
none			/proc		proc		defaults	0 0

# glibc 2.2 and above expects tmpfs to be mounted at /dev/shm for 
# POSIX shared memory (shm_open, shm_unlink).
# (tmpfs is a dynamically expandable/shrinkable ramdisk, and will
#  use almost no memory if not populated with files)
none			/dev/shm	tmpfs		nodev,nosuid,noexec	0 0


grub.conf : default 0
timeout 30
splashimage=(hd0,0)/boot/grub/splash.xpm.gz

title=Gentoo Linux
root (hd0,0)
kernel /boot/kernel-genkernel-x86-2.6.19-gentoo-r5 root=/dev/ram0 init=/linuxrc ramdisk=8192 ro real_root=/dev/sda2
initrd /boot/initramfs-genkernel-x86-2.6.19-gentoo-r5


message d'erreur au boot : 
block device /dev/sda2 is not valit root device
the valid block device is unspecified or not detected
please specify a valid boot device or a shell