[CLUE-Tech] Question on mounting a new scsi drive

[Matt Gushee]

On Sat, Aug 09, 2003 at 08:42:36PM -0600, Ken Kissinger wrote:
> I am new to Red Hat Linux and having a little trouble from a lack of
> understanding.
> 
> I installed Red Hat on an IDE 12 gig drive with no problems.
> 
> I am trying to add a second hard drive that is a 2 gig SCSI.
> 
> I installed the hardware, used fdisk to create a single partition:
> /dev/sda1
> 
> I used:  mkfs -t ext3 /dev/sda1  to make the file system without errors.
> 
> Then I have trouble trying to mount the drive, mount -t ext3 /dev/sda1
> /abc
> returns the message mount: mount point /abc does not exist.
> 
> How can I create a mount point, a directory, on a new drive when I can't
> mount the drive to create a directory ?
> 
> I am sure there is something simple that I am missing but I don't see it
> as yet.

Indeed. Your problem is not technical, but conceptual.

Have you run across the acronym VFS? It stands for "Virtual File System."
What it means is that the system gives you a consistent, unified view of
any number of storage devices. Here's a little command-line exercise for
you:

  $ cat /etc/fstab

If I do that on my desktop Linux box, I get this:

# /etc/fstab: static file system information.
#
# <file system>	<mount point>	<type>	<options>		<dump>	<pass>
/dev/hda3	/		    ext2	errors=remount-ro	0	1
/dev/hda10	none		swap	sw			0	0
/dev/hdc5	none		swap	sw			0	0
proc		/proc		proc	defaults		0	0
/dev/fd0	/mnt/fdext	ext2	user,noauto		0	0
/dev/fd0	/mnt/fdfat	msdos	user,noauto		0	0
/dev/fd0	/mnt/fdmin	minix	user,noauto		0	0
/dev/scd0	/cdrom		iso9660	ro,user,noauto		0	0
/dev/hdc1	/var	    reiserfs	defaults		0	2
/dev/hda7	/usr	    reiserfs	defaults		0	2
/dev/hda5	/home	    reiserfs	defaults		0	2
/dev/hda6	/opt	    reiserfs	defaults		0	2
/dev/hda8	/.devel	    reiserfs	defaults		0	2
/dev/hda12	/mnt/temp	reiserfs	user,noauto,exec	0	0
/dev/hdc8	/mnt/img	reiserfs	noauto	0	0
/dev/hdc9	/.scratch	reiserfs	user,noauto	0	0
/dev/hda1	/c		    msdos		user,noauto	0	0
/dev/hda2	/d		    msdos		user,noauto	0	0
/dev/sda1	/zip		ext2		user,noauto	0	0

This is showing 19 different devices that can be mounted on my machine.
There are two physical hard drives, a CDROM, a floppy drive, a zip
drive, and a virtual device (proc). There are 6 different file systems
(or 7 if you count swap space, but that's not a file system in the
normal sense). Now, my setup is a bit complex, but consider a really
simple configuration:

/dev/hda1   /       ext2    ....
/dev/hda2   none    swap    ....
/dev/hdc    /cdrom  iso9660 ....
/dev/fd0    /floppy auto    ....
proc        /proc   proc    ....

Or how about a setup that includes some network resources (NFS is
Network File System)?

/dev/hda1           /boot   ext2    ....
10.0.0.5:/.0/usr    /usr    nfs     ....

And so on. Now, here's the $64,000 question: from the point of view of
the end user (not the system administrator), what is the difference
between these 3 setups?

Answer: absolutely none.

That's what it means to have a VFS, and to my mind is one of the really
nice things about Unix-like systems in contrast to Windows. As a user,
you never have to worry about whether a file is on the C:, D:, E:, or
X: drive. If it's in /usr/local/lib, it's in /usr/local/lib. Where is
/usr/local/lib physically located? No idea. It could be on your first
IDE drive, or it could be on a server in another building. Assuming your
machine and the network are properly set up, you don't need to know.

(Well, of course, since you, like many Linux users, are your own system
administrator, you actually do need to know, but you *don't* need to
think about it in the normal course of your daily work).

So to get back to your original question--in case you haven't already
figured it out--all you have to do is:

    $ mkdir /abc

That directory is part of the VFS; it's not on any drive at all.

Hope that helps.

-- 
Matt Gushee                 When a nation follows the Way,
Englewood, Colorado, USA    Horses bear manure through
mgushee at havenrock.com           its fields;
http://www.havenrock.com/   When a nation ignores the Way,
                            Horses bear soldiers through
                                its streets.
                                
                            --Lao Tzu (Peter Merel, trans.)