[Mageia-dev] Grub2 vs. Grub Legacy in M3

Mon Jan 28 20:27:52 CET 2013

On 21/01/13 00:01, Frank Griffin wrote:
+> On 01/20/2013 02:58 PM, Maurice Batey wrote:
+>> On Sun, 20 Jan 2013 20:04:32 +0200, Thomas Backlund wrote:
+>>
+>>> http://svnweb.mageia.org/packages/cauldron/grub2/current/SOURCES/README.Mageia?view=markup
+>>>
+>>    Many thanks, Thomas!
+>>
+> Look, I don't don't want to restate the obvious, but you *do* realize
+> that in order for chainloader to work, you actually have to install the
+> secondary bootloader on the PBR of its owing partition ?  You can't just
+> have installed grub on your MBR at some point in the past, then install
+> grub2 (or anything else, for that matter) on the MBR again, and expect
+> your original partitions to boot ?
+>
+> In MGA install terms, and specific to the case of grub2 on the MBR
+> trying to boot grub on a PBR, you have to boot the grub partition (or do
+> the boot-elsewhere/chroot thing), modify the /boot/grub/install.sh to
+> not target the MBR (stage2=(hd0)) but indicate the PBR (stage2=(hd0,x))
+> and rerun install.sh to install grub on the PBR.
+Err...
+
+# grub
+root (hdx,y)
+setup (hdx,y)
+quit
+
+Job done - there is no need to touch install.sh
+
+>
+> In terms of the install paradigm, you have to choose to install the
+> bootloader to the PBR (sdaX) rather than the MBR (sda).  Otherwise, when
+> the MBR bootloader, whether grub2 or grub, boots and chains to the PBR
+> of the desired partition, there won't be anything there in the PBR to boot.
+>
+True, except as below...
+
+> If you need clarification on this, ask, and give specifics.  The
+> objective of chainloading is to have each PBR (partition) behave as if
+> it is its own MBR.  If you try to point grub2 menu entries to native
+> partiton grub files, or vice versa, you are just asking for trouble. The
+> clean way to do it is to use chainloading to link the MBR (whatever it
+> is) to the PBR (whatever it is), and let the PBR do the bootloading for
+> its own partition according to its own needs.
+
+...this is where we disagree slightly ;)
+Chainloading into grub2 is not the best way, due to the block lists 
+problem people keep mentioning and complaining about.
+Grub2 can install it's kernel in the root filesystem which can be booted 
+directly. Installing the grub2 package, whether during install or later 
+automatically builds /boot/grub/i386-pc/core.img and also creates a 
+grub.cfg ready for use.
+Chanloading is un-necessary since an entry in menu.lst on a legacy 
+system will boot a grub2 Mageia system using:
+
+  	title Mageia via GRUB 2
+	root (hdx,y)
+  	kernel /boot/grub2/i386-pc/core.img
+
+...as explained in the above README.Mageia
+>
+> If you do it this way, you can install whatever you want as a bootloader
+> on the MBR, and each partition can have whatever BIOS-compliant
+> bootloader it wants, including grub, grub2, lilo, OS/2, DOS, or Wndows.
+>
+Yes, I use a small grub2 partition sda1 as "master".
+To boot into Mageia grub2 systems I use the grub2 multiboot command:
+
+	menuentry 'Mageia-3 multi sda6' {
+	search --no-floppy --label --set=root mageia-3
+	multiboot /boot/grub2/i386-pc/core.img
+	}
+
+So IMO all of the FUD about "you can't install grub2 to the PBR" is 
+pointless since it's just not necessary.
+
+My 2 cents ;)
+
+