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JoeLinux 01-29-2002 10:10 PM

LFS without a host system? (read on..I need more subject space than I have)
 
I have begun my quest into LFS (kinda. I started downloading the stuff, and I only have an hour left). But, I have been wondering.

How do the distros bootup into a fully working system with minimal capabilities with nothing at all to work off of. For Gentoo (www.gentoo.org) the boot cd puts you into a fully working (seemingly) but limited system, with only a few commands, but the only ones that you need. How do they do that?

I would like an explanation as detailed as you wanna give me. Don't dumb it down.

lfslinux 01-29-2002 10:22 PM

Re: LFS without a host system? (read on..I need more subject space than I have)
 
Quote:

Originally posted by JoeLinux
I have begun my quest into LFS (kinda. I started downloading the stuff, and I only have an hour left). But, I have been wondering.

How do the distros bootup into a fully working system with minimal capabilities with nothing at all to work off of. For Gentoo (www.gentoo.org) the boot cd puts you into a fully working (seemingly) but limited system, with only a few commands, but the only ones that you need. How do they do that?

I would like an explanation as detailed as you wanna give me. Don't dumb it down.

You may want to post this in the Linux From Scratch forum (under the Distribution forum)?

Secondly, I'm not quite understanding your question I'm afraid. Perhaps you can dumb it down for me a bit ;)

Mik 01-30-2002 03:33 AM

I'm not sure if I understand your question fully. But I think you wanted to know how they get an os running without installing anything to your harddrive.
Booting from cdrom is done kinda similar to booting from floppy. There is actually a boot image on the floppy. This image can be 2.8mb and is kinda seen as the same way as the floppy image would be seen. Later on in the booting stage after it recognizes the cdrom filesystem it can read the rest of the files on the cd for whatever actions need to be done next.
The only real problem is that a cdrom is only readable and not writeable. So what gets done is a ramdisk gets created to write files too. If you look at the layout of the basic linux directory structure. The only directories that will need to get written too when running is /var and /tmp.
If you follow that layout you can create a bootable cd which can do almost anything without ever needing a harddisk.

JoeLinux 01-30-2002 12:46 PM

Thanks!
 
Well, you understood the question perfectly That was just what I wanted to know. So, basically, it would be a boot image on a CD, that then copies files onto a RAMdisk, which can then run like on a hard drive. That seems pretty simple. The technical details are left out though =( Anyone know a good site on how to do this? Or am I oversimplifying this.

notsoevil 01-31-2002 04:30 PM

First, this whole thing sounds familiar. :)

see: http://www.linuxquestions.org/questi...threadid=12234

Second, see:

http://hints.linuxfromscratch.org/hi...ot-cd_easy.txt
http://hints.linuxfromscratch.org/hints/bootcd.txt
http://hints.linuxfromscratch.org/hi...bare_build.txt
http://www.bablokb.de/bblcd/

I am currently (as the first thread above kinda shows) trying to do something similar. I will provide full details when done.


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