[ale] The boot question

[Jeff Hubbs]

I don't understand your question but I'll try to answer what I think you're
trying to ask.  Good newbie food here in any case, I hope.

Linux adopts the POSIX/UNIX concept of an upside-down tree structure with
"root" (specified as simply "/") at the very top.  Everything underneath is
treated as a file:  a device is a file, a directory is a file, and a file is
a file.  

The connection between disk partitions and parts of the filesystem tree is
typically established at install time.  An abstract way of looking at it is
that you "hang" disk partitions (which are named entities within the first
level "/dev" directory) on the tree that is to be created (/dev and /proc)
are not "real disk space."  The places where you hang them are called "mount
points."  The simplest arrangement you can have is a single partition, say,
/dev/hda1 (for the first partition on the only hard drive), in which case
you'd hang it on the mount point of "/".  When you run fdisk, Disk Druid, or
some GUI tool to set up partitions, you can go wild and make separate
partitions for /home, /var, /usr/local, just whatever.  

I have a 486SX/33 that I'm setting up as a DNS/DHCP server using Red Hat
6.2, and its ISA-card IDE controller is so old that an 850MB drive can't be
booted to.  I have some 340MB drives that do work, but just one of them
isn't big enough, so I went to another RH6.2 machine, ran a du, and saw that
/usr/bin and (I think?) /usr/lib would both fit comfortably on a 340MB
drive.  I hooked up two 340MB drives in the machine and set up partitions
and mount points something like this:

/dev/hda1	300MB	/
/dev/hda2	32MB	<swap>
/dev/hdb1	256MB	/usr/bin
/dev/hdb2	77MB	/usr/lib

and everything fits.  

So, you can use this ability to assign different roles to different drives
and to different partitions on different drives.  What's cool about this is
that you can leverage your drives' uneven performance.  On this machine,
/usr/bin and /usr/lib are read-only for the most part, so they went on the
340MB drive with the 64KB cache (as determined at kernel boot time and
revealed with the dmesg command).  The other 340MB drive had a 128KB cache,
so that's where I put the swap partition (lots of read-write).  Given a
choice of drives, you want to put the things that require speed on the drive
or drives with the most heads and/or the bigger cache, because electronics
are generally always faster than mechanicals.  Put up some 16-head 2.1GB
drive up against a 2-head 2.1GB Quantum Bigfoot drive and you'll see what I
mean (the Bigfoot is ridiculously slow!)

- Jeff



> -----Original Message-----
> From: moisey.g.oysgelt at mail.sprint.com
> [mailto:moisey.g.oysgelt at mail.sprint.com]
> Sent: Wednesday, April 11, 2001 8:26 AM
> To: ale at ale.org
> Subject: [ale] The boot question
> 
> 
> I'm just starting with Linux.
> 
> Can you help me to understand the order how Linux processes files and 
> directories.
> 
> I need this to know  how  proper to install software.
> 
> Thanks Moisey
> 
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