making initrd for sarge 2.6 kernel, error using mkinitrd)

["Benedict Verheyen" <linux4bene@telenet.be>]

Hi,

i'm having trouble making an initrd (that works) for a custom compiled
kernel. If i use the 2.6.7 sarge kernel and using lvm2 (only boot not on
lvm2)all is well. I wanted to compile the 2.6.8 kernel & activate the
framebuffer amongst other things. I can compile a kernel fine it gave me a
Kernel panic: VFS: Unable to mount root fs on unknown-block(0,0)

I then restarted the whole process and copied over the config of the 2.6.7
without changing
anything, yet the resulting error is the same
"Kernel panic: VFS: Unable to mount root fs on unknown-block(0,0)"

So i thought the initrd is the problem and tried making my own initrd:
mkinitrd -o /boot/initrd.img-2.6.8.10sep2004 2.6.8.10sep2004
This returns with an error:
/usr/sbin/mkinitrd: /dev/mapper/main-lv_swap: Kernel does not support LVM

Weird because the standard 2.6.7 kernel in debian does support it and mine
as well:
CONFIG_BLK_DEV_DM=y
Also, when running mkinitrd, does it run necessary commands to load a root
on LVM?
This would be at least vgscan followed by vgchange -a y

Some more info:
1) I compiled the kernel with this line:
make-kpkg --initrd --append-to-version=.10sep2004 kernel_image modules_image

then installed without problems

2) grub
title Debian GNU/Linux, kernel 2.6.8.10sept2004
root (hd0,0)
kernel /vmlinuz-2.6.8.10sep2004 root=/dev/mapper/main-lv_root ro
ramdisk_size=100000
initrd /initrd.img-2.6.8.10sep2004
savedefault
boot

If first thought the error might be due to not having enough ramdisk_size
or specifying the root disk the wrong way. But it should be the same as
the standard installed kernel.

* cat /proc/partitions

major minor     #blocks     name
 3       0     14668416    hda
 3       1        97744    hda1
 3       2     14570640    hda2
254       0       258048    dm-0
254       1       258048    dm-1
254       2      8388608    dm-2
254       3      1048576    dm-3
254       4       512000    dm-4
254       5       258048    dm-5

* cat /proc/devices
Block devices:
 1 ramdisk
 3 ide0
22 ide1
254 device-mapper

* ls -la /dev/mapper/main-lv_root
brw------- 1 root root 254, 0 Sep  3 19:16 /dev/mapper/main-lv_root

* perl -e 'printf "%02x\n", 254'
-> fe

So i tried using fe00 as the root device in grub but that doesn't work
either as i then get this error:
Kernel panic: VFS: Unable to mount root fs on unknown-block(254,0)

I then tried something like this as kernel line:
kernel /vmlinuz-2.6.8.07sep2004 ro root=fe00 devfs=mount ramdisk_size=100000
because i thought that maybe devfs was to blame but again, no go.

So why is this kernel unable to load the root file system while it has the
same config as the standard kernel?


Thanks,
Benedict