[lug] booting and kernel compiling (was dumpdates)

D. Stimits stimits at idcomm.com
Mon Aug 14 17:58:54 MDT 2000

Wayde Allen wrote:
> On Mon, 14 Aug 2000, John Starkey wrote:
> > > You could probably think of it that way.  In Linux, the kernel, the file
> > > system, and the collection of program is all called a distribution.  If
> > > you are a purist only the kernel program itself is actually Linux.
> > > Everthing else is someone's idea about what constitutes a good file
> > > structure, and a collection of GNU/OpenSource software.
> >
> > What exactly is needed for linux to boot then? Just the Kernel?

Remember that libc (or glibc, or some version) is required for almost
everything. While modules in /lib/modules/ can be removed for many
things, take out libc, and you've basically cut the spinal cord. Much of
what the kernel does to relate to other programs involves it. As an
experiment, run ldd on programs in /bin or /sbin that you consider
essential, probably none of them live without libc, but many need only
that and the linker (which is another good one not to destroy).

> Hmmm ... that is a good question.  In a sense I guess it depends on what
> you define as booting.  If the bios works, launches the boot loader, and
> that in turn gets the kernel loaded I guess you could argue that the
> system is booted even though there are no programs available to run.
> You might want to check out my Linux Newbie articles at
> <http://lug.boulder.co.us/docs.html>.  In particular check out
> <http://lug.boulder.co.us/docs/newbie02.html>.
> > I know I
> > lost all my /bin like mv which is why I rebooted to floppy. My
> > understanding, which is reinforced by this conversation, is that the
> > Kernel calls individual, small, programs like mv when it needs it, or
> > actually your call to mv makes the kernel search it out via $PATH.
> You've kind of got this backward.  The kernel is really just a
> standardized interface to the system hardware.  It doesn't have a reason
> or desire to call the mv command.  That is where you come into the
> picture.  You were the one who tried to invoke that command.  The path is
> part of the shell environment that you interact with.
> > So would it be safe to say that I can boot but if I don't have /bin it's
> > just gonna sit there smil'in?
> That is correct.
> > /sbin is the kernel's equiv of /bin?
> No, /sbin is where programs typically used by the system administrator
> reside (See http://lug.boulder.co.us/docs/newbie05.html).
> > I did do a make modules and gathered that that's what it does.
> Yeah, it should create an object file for the modules in your source
> distribution and update your /lib/modules, but that is all.
> > I was actually referring to the image from bzdisk
> OK, but my point is that a boot floppy simply kick starts the system,
> mounts the root file system from your hard drive, and at that point is
> basically done.  If the root file system has been modified from its
> original form the boot floppy won't know what to do with it.  In other
> words, it relies on the /bin directory for essentially all of its
> programs.  A rescue floppy, install disk, or installation CD, on the other
> hand doesn't (can't actually) make this assumption.
> > > I like your willingness to experiment!
> >
> > Thanks, would you mind making the mistakes for me :}
> Most of us have already made the mistakes.  The trick is for you to figure
> out how best to make use of what we've learned.
> - Wayde
>   (wallen at boulder.nist.gov)
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