GRUB discussion follow up ?

[Jacques B.]

> I don't see it as hijacking.  It certainly follows up on the Grub
> discussion.
>
> I have been scratching around as well.  I came up with more new
> questions than answers.  But it seems to me that understand GRUB, it has
> to be completely disambiguated (to borrow a Wikipedia term) from Linux
> or any other Operating System first.  Only then adding in how Linux gets
> loaded.
>
> That means understanding the following in their proper order:
> 1) BIOS in general
> 2) How BIOS originally writes disk and partition locations to the MBR
> or after installing a new harddisk. It must have some BIOS info even if
> 'fdisk', 'parted' or 'mkfs' are used as part of the installation.  I
> don't know if these are even involved but I plan to check.
> 3) What code system it uses to designate disks and partitions.  I have
> found three or four sites that break down the meaning of binary code bit
> by bit.  That needs study.
> 4)How to install Grub on a cd-rw.  That will separate the men from the
> boys and explain how BIOS finds GRUB and how GRUB finds the operating
> system.  It should also explain how stage 1.5 gets where it is going.
> 5) How the MBR binary code might vary from the code GRUB uses?
> 6) Does GRUB get its disk and partition information from BIOS ROM/CMOS
> or from RAM after BIOS has been loaded?
> 7) Where is stage 2 installed?  How big is it?  It seems to have a lot
> of different file systems data and CLI commands available for just a
> tiny system.  How does it use the grub.conf file?  Is it just a C
> compilation or does it have some aspects of an interpreter?
> 8) (more properly 5b)) Because GRUB is so rudimentary and used so early
> in the boot process, what processes and data are NOT available to it
> until an operating system is loaded. Or, does it have a way of getting
> at some data before Linux is loaded eg device.maps, system.map and
> menu.lst/grub.conf.  How does it use /boot/grub/e2fs_stage1_5,
> fat_stage1_5, reiserfs_stage1_5 etc.?
> 9) Where does the menu gui come from?
> 10) When -- exactly -- (on what line of GRUB code) does GRUB begin
> loading the Operating System?
> 11) How does it load from a cd-rom, from a stand alone partition, from
> another computer?  Particularly if no other system is yet running.
> 12) One more disambiguation between GRUB and the Operating System
>
> Jacques, your points have given me an opportunity to list the current
> questions I have.  I know I have found some of the answers already.  I
> just have to read through them and put them all into a meaningful
> context.  Other questions and answers I now feel confident I can chase
> down. (Probably have to look at some source code.  I hope not -- that
> can become a cascading disease.)
>
> --
> Regards Bill
>
> --
> fedora-list mailing list
> fedora-list at redhat.com
> To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list
>

Thanks Bill.  I re-googled the Linux boot process and one of the
references I found a while back that I re-found is:
http://www.ibm.com/developerworks/library/l-linuxboot/index.html

Being from IBM it has more credibility than an individual's personal
site (not to devalue the latter, just that one must always assess the
credibility of online sources/resources).

Another is from RedHat at
http://www.redhat.com/docs/manuals/linux/RHL-9-Manual/ref-guide/s1-boot-init-shutdown-process.html
I don't believe I had read that one.  Must go back and read that when
I have to get my head back into the boot process.

I also came across http://oldfield.wattle.id.au/luv/boot.html today
which I hadn't looked at before.  It's very simplified.  I haven't
scrutinized it yet for accuracy and I don't recognize the domain as a
trusted source so take it accordingly.

And this one http://itreviews.blogspot.com/2006/05/linuxs-boot-process-explained.html
is a personal blog.  Again we must take it with a grain of salt.
There are a number of feedback postings on it which can help either
validate or question some of the blogster's facts.

I'm wondering if a very stripped down distro might make it easier to
determine some of this.  It would eliminate some of the possible
extras the mainstream distros probably add to the process.

Thanks,

Jacques