I've seen losts of posts and tutorials on this subject but maybe I've spent too much time with windows and file structures where I can see where the copied files are going when I move them.
Under Madriva 2007 I recently added 320GB sdb to my PC created a 200GB sdb1 partition wanting to keep 100GB for Windows files.
My big mistake was to accept Mandrivas suggestion of using /usr as a mount point and letting it copy files to sdb1.
I realised later that a better move would have been copying /home to sdb1.
I did this:
mkdir /mnt/home
mount -t ext3 /dev/sdb1 /mnt/home
cd home
cp -ax * /mnt/home
and now I find that I have the following:
sda6 /home-geoff,lost+found
sdb1 /usr-bin,etc,games,geoff,include,java,lib,local,
lost+found,sbin,share,src,tmp,X11R6
looks like I've got a copy of /home inside the /ust directory.
My fstab looks like this:
/dev/sda1 / ext3 defaults 1 1
/dev/sda6 /home ext3 defaults 1 2
/dev/hdb /mnt/cdrom auto umask=0,users,iocharset=utf8,noauto,ro,exec 0 0
/dev/hda1 /mnt/win_c ntfs umask=0,nls=utf8,ro 0 0
/dev/hdc1 /mnt/win_c2 vfat umask=0,iocharset=utf8 0 0
none /proc proc defaults 0 0
/dev/sdb1 /usr ext3 defaults 1 2
/dev/sda5 swap swap defaults 0 0

I guess I'm not understanding the mounting points!
what I want is /home on sdb1 and the rest on sdax
can anyone help

Looking through my notes from when I did this a few years back, here's what I did:

>install new drive - using your name sdb
>create partition /sdb1
>mv /home /home.old
>mount /dev/sdb1 /home
>cp -a /home.old/* /home
>echo "/dev/sdb1 /home auto defaults 0 1 ">>/etc/fstab
>rm -rf /home.old

This was on an old redhat 6 box. Seems that I should have removed the old /home reference in the fstab? Maybe I didn't have a separate /home partition? Been too long.

Since you copied /home to /usr on sdb1, /home is still safe and sound under the root of the file system.

So, start by deleting /geoff from /usr. Now /usr is clean.

mkdir /mnt/usr to create a directory into which to copy or move /usr.

'cp -Rax /usr/* /mnt/usr' to copy /usr to sda1, or 'mv /usr/* /mnt/usr' to move /usr to sda1.

If you used the mv command, sdb1 should now be empty.

Edit /etc/fstab to change '/dev/sdb1 /usr' to '/dev/sdb1 /home'.

mkdir /mnt/home

Unmount /dev/sdb1 and remount it with: mount /dev/sdb1 /mnt/home.

Copy (or move) the contents of /home to sdb1.
cp -Rax /home/* /mnt/home

Reboot. /usr should be under the root of the filesystem on sda1, and /home should be on sdb1.

All that's left to do is clean up.

rmdir /mnt/usr
rmdir /mnt/home

Your most safe method would be to do it all from a liveCD instead of the running system. The mount points and commands given above would have to be changed slightly if working from a liveCD.

Thanks a lot Larkl and bigrigdriver, my system is as I want it and at last I've understood the logic behind the steps.
I even dared to use Gparted to increase the size of my root directory (now 15gb) and swap file (6gb) seing as I've got lots of space to spare. Gparted worked perfectly.
Thanks again
Geoff