Re: What exactly does it take to boot Linux?

From: Philip Dodd (pd_at_phildoddNOSPAMfreeserve.co.uk)
Date: 03/25/04 

Date: 25 Mar 2004 14:47:38 GMT

On 24 Mar 2004 23:05:48 -0800, David <blixel@yahoo.com> wrote:
>I was just sitting here (bored) and I started to wonder what exactly
>does it take to make Linux boot?

Difficult to remember everything - you've forgotten the Linux loader and
LIBC before the kernel gets as far as calling init....

Adding to what others have said, have a look at the Bootdisk-HOWTO , available
at http://www.tldp.org in the Howto section.

Written in an easily-understood fashion by Tow Fawcett, it explains much more
than just making boot disks.

Referring to the Howto, I set up an old Pentium 75 with 8 Mbytes of RAM and
no CD-Rom, as a very efficient X terminal. What is required as a minimum to
"make Linux boot" is implicitly explained as part of the process of creating
the boot disk.

There is the option of creating a single boot diskette. Making a 2-disk
system of boot and root diskettes is more useful, especially for running
diagnostics. Most useful of all, especially for building a new system from
floppies is the third option of boot+root + unlimited supplementary diskettes.

My conversion of an old PC to an X terminal needed boot+root+ 6 diskettes
of additional software to format the hard drive, install the file structure
and device files, the kernel and init files, the C library and X server,
along with essential utilities. After that I lost count as FTP was working.
It soon becomes clear which software is needed - usually library files -
when other software complains of it being "missing" - one way of building a
minimalist system but not for the nervous !

Give that a go. You can of course run a machine from boot disks without
necessarily overwriting anything on the hard drive. Try the rescue sets
available on Ibiblio, such as BanShee Linux ( although if you try that one,
be aware that it has unique user and device heirarchy which takes a bit of
fathoming out initially ). BanShee doesn't try to be "all-singing" etc
like Tom's disk, and is easy to relate to the Bootdisk HOWTO.

I built two systems in the past following "Linux from Scratch" instructions
( although these days do my own thing of LID - Linux In Desparation.... )
LFS is very useful as a fully comprehensive list of what needs to be done
to set up an operational Linux system to "distribution" level, which might
be more than you're looking for at present. You are right in your
suspicion that there is a minimalist amount that you need to get a system
running, but when you go to the next stage of building a full system the
LFS instructions are invaluable.

We're all probably a bit nervous of suggesting a "definitive list" of "what
makes Linux boot", but experimenting with boot diskettes as in the HOWTO
mentioned above is a practical way of finding out.

Philip Dodd 

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