DISCUSSION: Chainloading in Linux

This thread is to discuss the article titled: Chainloading in Linux

Content is good -- I do most of this myself.

It would be nice see a distinction made between a boot loader & a boot manager (such as GAG). We get so used to the fact that the common bootloaders we encounter also function as boot manager's, that we forget the distinction.

Any chance this can be edited to fix the following:

• "chainlader +1" (1st occurence)
• make the "Quote:"'s into Code blocks
• make the bold tags work instead of being visible as text.

Originally Posted by archtoad6 Content is good -- I do most of this myself. It would be nice see a distinction made between a boot loader & a boot manager (such as GAG). We get so used to the fact that the common bootloaders we encounter also function as boot manager's, that we forget the distinction. Any chance this can be edited to fix the following: "chainlader +1" (1st occurence) make the "Quote:"'s into Code blocks make the bold tags work instead of being visible as text.

This thread was very good in explaining chainloading. However, how does bootloader of System A actually find the bootloader of System B? How does it read it in an execute it?

Since Windows is in a fixed location, is the boot.ini file executed?

I have been using Grub for years now and I never really understood how chainloading actually worked. I am interested in chainloading other Linux distros but I thought I would try to understand what chainloading actually is before I do so.

Thanks
-Wit

Originally Posted by witE.fellow This thread was very good in explaining chainloading. However, how does bootloader of System A actually find the bootloader of System B? How does it read it in an execute it? Since Windows is in a fixed location, is the boot.ini file executed?

The bootloader of System A finds the bootloader of System B because you tell it where to look. An example of GRUB:

title Linux @ hda7
root (hd0,6)
chainlader +1

The root section tells GRUB where the / of System B is. / of System B is also where the bootloader of B resides. So in practice the first bootloader comes up and you point it to B, then the second bootloader comes up and you choose what to boot from there.
One advantage to this setup, if you have multiple Linux installs or you are testing new distros, is that you can boot into the new install right away without booting first into your main install to reconfigure the bootloader.

Hope that makes some kind of sense.

If that isn't clear, you might want to look at the on-line manual for GRUB: http://www.gnu.org/software/grub/manual/grub.html


13.3.31 root explains "root".


11.1 How to specify devices explains "(hd0,6)".

13.3.4 chainloader explains "chainloader +1".


FWIW, 11.3 How to specify block lists suggests that the 2 commands could be combined as "chainloader (hd0,6)+1"

Chainloading for non-Linux systems..

if the os' file system is not supported (like in opensolaris with ZFS) you need to replace root with rootnoverify. Because you will get Unsupported File System error when grub tries to mount the partition.

Other then that, nice guide this helped alot!

thanks,

djgerbavore

Good reminder, I almost never need rootnoverify, so I forget that it's sometimes necessary.

Very nice info, lots of stuff I tend to forget.