When dual booting between 2 linux distros i see guides saying that you need to chainload grub from the MBR to the 2nd root partition. Why can't you just add a second entry into the MBR bootloader to boot the 2nd distro directly?

Thanks

You can actually use for both OS the same grub. But the problem is that you should install the second without grub and configure grub.conf manually(in the OS that has grub) . I know at least how you can install Debian without grub. But I cannot say anything else about other systems
You see, there are two kinds of people in Linux: the first kind wants everything to run out of the box, and the second kind love to use their brains and set up the OS as they want. IF you are from the first kind, do chainloading. If you are from second, the kernel doesn't care from what version of grub it was loaded

it depends on the grub you are using and the distro your trying to boot into. some grubs will not boot a slackware formatted partition, therefore will have to chainload. Since you have Slackware, Slackware grub should boot just about any distro, but not sure about ext4 formated partitons.

That's news!! How many versions of GRUB do you think there are? I'm using 0.97 and it boots Slackware with both eyes closed. In the same vein, what is "Slackware grub"?

"slackware-formatted partition" ?? No clue what that is.....

It is possible that the issue here is that 0.97 will not boot certain filesystems. I'm pretty sure everything here is ext3.

I have never used GRUB 2, so no clues there.

I believe like pixellany, the only mention I have heard is somewhere I read if you are using an ext3 and one ext4 of course using grub 0.97 and grub 2 that the easiest is to chainload.


Larry

Either the guides you are reading are not clear or you are not understanding them. Using Grub, you have the stage1 file (512 bytes) in the master boot record which points to the stage2 file of the system you are using to boot. When you see the boot menu on your screen, you are in the stage2 file of the primary OS - the one you use to boot.

If you have entries in that menu.lst file similar to the one below pointing to a partition with kernel and initrd files, you don't need a boot directory on that partition, it will still boot. Should be obvious because it's pointing to the kernel not a menu.lst file:

If you have a configfile entry such as the one below in your primary menu.lst, you will need the menu.lst file at least in that boot directory.

I'm not sure what the difference might be with Grub 2 as I haven't used it yet.

Grub (classic) needs to be patched to support ext3 (and ext4) using the 256 byte inode. It's not a Slackware specific issue. A currently installed grub will not handle such a (new) filesystem - and this is the default inode size these days for mkfs for both ext3 and ext4.

what syg00 says is what I'm talking about. I came across it when I upgraded to 12.1 slackware and the grub from another distro would not boot it. before ext4 came out slackware was the only distro I was having trouble booting from other distros grub installations.

Yes you can use the same grub to boot 2 systems and can take it even a bit further and use the same /boot partition to boot different Linux distributions. Chainload is when you install grub into the partition and not into the MBR.

As for grub not booting some things this is kinda true about ext4. Grub cannot have its files or the kernel ( I think ) on a ext4 partition because currently there is no support "yet". This was the last I have seen regarding grub and ext4 its possible they have a new version out there that does boot it now. The advantage of having both systems share the /boot section is that you only have one place to update the menu.lst file and one place grub has its files. If you opt to not do this remember that the kernel image has to be somewhere grub can access it without needing drivers.