[PLUG] Redhat 7.3.92 so far...

Russell Senior seniorr at aracnet.com
Tue Jul 16 06:32:18 UTC 2002


>>>>> "Eric" == Eric Harrison <eharrison at mail.mesd.k12.or.us> writes:

Eric> Try fiddling around with GRUB for a while. I won't use LILO
Eric> anymore, GRUB is much harder to screw up - and if you do screw
Eric> it up you can drop down to a command prompt giving you a chance
Eric> to fix the problem and get the machine back up and running.

Alan> I need to find a good overview of how GRUB is supposed to work.
Alan> The commands are a bit alien to me.

Eric> Here's 99% of what you need to know about grub under "usual"
Eric> conditions:

Eric>  * The config file is /boot/grub/grub.conf (symlinked to
Eric> /etc/grub.conf), you should be able to get the syntax down in
Eric> about 15 seconds. The "default=?" line is the default kernel, as
Eric> listed counting from zero.  (i.e. the first kernel listed is
Eric> "0", the second is "1", and so on)

On Debian, I think this file is typically located in
/boot/grub/menu.lst.  One of mine looks like this:

   default saved
   timeout 5
   serial --unit=1 --speed=9600
   terminal --timeout=5 serial console

   title   Linux 2.4.18
   root    (hd0,0)
   kernel  /boot/vmlinuz-2.4.18 root=/dev/hda1 console=ttyS1,9600
   savedefault

   title   Linux 2.4.16
   root    (hd0,0)
   kernel  /boot/vmlinuz-2.4.16 root=/dev/hda1 console=ttyS1,9600
   savedefault

The savedefault stuff is to remember what you booted the last time and
make it the default.

You can install GRUB to a boot floppy while you are getting used to
it.  Then "grub-install" to the hard disk when you are more
comfortable.

See the GRUB manual for details:

  <http://www.gnu.org/manual/grub/index.html>

Eric>  * you don't need to run a command after editing the grub.conf
Eric> file, GRUB reads it when the system boots

Right.  As I understand it, LILO sort of "cooks" a boot environment
for you, a static sort of thing.  GRUB, on the other hand, is more
dynamic.  It groks file systems, reads text configuration files or
interactively-provided configurations during the boot phase.  While
booting, you can use GRUB to search for kernels, do tab-completion,
etc.  Just way more flexible than LILO.

Eric>  * I don't want to reboot right now, am too lazy to RTFM, and
Eric> can't remember off the top of my head how to drop down to the
Eric> "boot monitor" prompt.  I believe it's listed right on the
Eric> initial bootup screen. There is a help facility that explains
Eric> the basics of each command. The big "gotcha" for me was that if
Eric> /boot is a seperate partition, grub acts as if it chrooted to
Eric> there (i.e. "/boot/vmlinuz" is "/vmlinuz" to grub).

Ah yeah.  While GRUB groks file systems, it doesn't grok /etc/fstab
AFAIK, so your filenames are relative to the filesystem root.  GRUB
doesn't know that your boot partition is going to be mounted under
/boot, so you give it a root device descriptor (hd0,0) or whatever,
and the kernel path is relative to the root of that filesystem.



-- 
Russell Senior         ``The two chiefs turned to each other.        
seniorr at aracnet.com      Bellison uncorked a flood of horrible       
                         profanity, which, translated meant, `This is
                         extremely unusual.' ''                      




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