[lug] dumpdates

Wayde Allen wallen at boulder.nist.gov
Mon Aug 14 11:23:42 MDT 2000

On Mon, 14 Aug 2000, John Starkey wrote:

> > What kinds of things are you
> > moving around and why are you moving the /lib files?  Nothing should need
> > to move to compile or recompile.  
> See above. When I re-compiled I disabled modules support. Then I noticed
> in /lib/modules that everything was still there.

Yes, just because you compile a kernel not to use the module library
doesn't mean that the module library should go away.

> So "what the hell" I decided to try renaming everything else I thought the
> kernel would replace, knowing that it'd boot from the floppy or CD no
> matter what.

It sounds to me like you don't quite understand what a kernel actually is.

The kernel is really just one single file.  If you go to your root
directory you should see something like vmlinuz, or in your case perhaps
bzlinux, ... whatever.  That is your kernel, it is just one executable
file that the boot loader starts at boot time.  When you compile a new
kernel you make a new one of these and copy that to your root directory. 
To make the new kernel boot, you have to tell the boot loader (usually
LILO) where, and what it's name is. 

All of thee other stuff you are tinkering with is the source code and the
compiler library files.  The kernel will either use something from the
libraries (modules) if you tell it to or not.  Moving your /lib stuff
around just trashes your compiler, and any programs that make use of
shared libraries. 

> The floppy image was gave me the same kernel panic.

It probably either tried using a library you renamed, or mounting
something that you've moved.

>  So I
> tried CD. And I think I forgot to take the floppy out, because the CD
> didn't boot.

Sure that will do it.

> So that's where I started to get scared. Later the CD did boot. And my
> panic stricken research really learned me a lot :}

Yeah, you learn a lot doing things like this.  The CD will boot since it
doesn't reference anything on your hard drive.

> > Keep in mind that you
> > can have as many kernels in your root directory as disk space and desire
> > allows.  You put entries in your Lilo.conf file to point to each kernel
> > file.  That way you can start whichever one you want.
> This is the route I'll take in the future. I didn't totally understand the
> HOWTO regarding this technique and heard that it can be done without this.
> So for newbie sake I did without.

OK, although that just means you need a different boot loader if you
aren't using LILO.  The game is the same.

For LILO if you should have a file /etc/lilo.conf that looks something

image=/vmlinuz  <--------- This is default kernel since it appears first
other = /dev/sda1 <------- This is my dual boot Windows NT (never used it)
   label = WinNT
   table = /dev/sda

So if you compile a new kernel and want it to be bootable you'd modify
this file so it reads something like:

image=/bzlinuz      <---- give the name of the new kernel
   label=New_Linux  <---- give it a title in the boot menu
image=/vmlinuz      <---- leave the old kernel intact in case you need it
other = /dev/sda1
   label = WinNT
   table = /dev/sda

Next all you do is type the command lilo to run the lilo program.  The
next time you reboot your machine the new kernel will be the default, or
you can choose the old kernel (or other OS) by hitting the tab key to get
the menu and selecting the appropriate entry.

- Wayde
  (wallen at boulder.nist.gov)

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