What are the two roots in grub?

[hendrik@topoi.pooq.com]

Do I understand this correctly?

In my /boot/grub/menu.lst there is a stanza

title		other: Debian GNU/Linux, kernel 2.6.18-3-486
root		(hd0,7)
kernel		/vmlinuz-2.6.18-3-486 root=/dev/mapper/lovesong-other ro 
initrd		/initrd.img-2.6.18-3-486
savedefault

(I edited the title fro what the installer gave me)

Does this mean that grub will look in (hd0, 7), which is the same as 
/dev/hda8, which is the fourth partition in the extended partition, to 
find the file /vmlinuz-2.6.18-3-486, and then use that file as a kernel 
to boot Linux, mounting /dev/mapper/lovesong-other on /
?

Or does it get its kernel from the file /boot/vmlinuz-2.6.18-3-486
directory in /dev/mapper/lovesong-other?

It's confusing top have two things called root.

One thing I do seem to appreciate is that the menu.lst file is 
independent of the system from which one runs grub.  This is much more 
convenient than lilo, where all files are described relative to the 
current / directory.

---

I'm having touble with another stanza, which I wrote myself by analogy:

title		etchtobe boots from /dev/hda5; Debian, kernel 
2.6.8-2-386
root		(hd0,4)
kernel		/vmlinuz-2.6.8-2-386 root=/dev/mapper/lovesong-etch ro 
initrd		/initrd.img-2.6.8-2-386
savedefault

This is intended to boot a sarge system which I plan to upgrade to etch.
Its /boot is on /dev/hda5, and /dev/mapper/lovesong-etch is to be 
mounted on / .

But, not being able to boot this sarge-to-become-etch system yet, I run 
grub from another sarge system.

The mount command (on this other system) tells me:
  /dev/hda5 on /etch-boot type ext3 (rw,errors=remount-ro)
  /dev/mapper/lovesong-etch on /etch type ext3 (rw,errors=remount-ro)
and the relevant files appear to be in the right places:

ls /etch-boot
lovesong:/# ls etch-boot
boot.0200   config-2.6.7-1-386  initrd.img-2.6.7-1-386  sid.bmp
boot.0300   config-2.6.8-2-386  initrd.img-2.6.8-2-386  System.map-2.6.7-1-386
boot.0800   debian.bmp          lost+found              System.map-2.6.8-2-386
boot.0810   debianlilo.bmp      map                     vmlinuz-2.6.7-1-386
coffee.bmp  grub                sarge.bmp               vmlinuz-2.6.8-2-386
lovesong:/# ls /etch
april   etch-boot   initrd.img.old  offsite-ms     sbin        
usb-reiser
backup  farhome     lib             opt            srv         usb-vfat
bin     farusr      lost+found      proc           sys         usr
boot    freshetch   media           prufrock       tmp         var
cdrom   gentoo      mnt             quota.group    topoi       vmlinuz
cdrom1  home        mount-reiser    quota.user     topoi-home  vmlinuz.old
dev     home2       newsarge        reiseroffsite  topoi-www   woody
etc     initrd      offsite         root           usb-ext3
etch    initrd.img  offsite-ext2    sarge          usbkey
lovesong:/#


But when I boot this sarge-to-become-etch system, after giving me the 
two lines of partition information, it stops with a complaint about root 
pivot.

-- hendrik