I have RedHat9, mailserver, webserver, etc. (so I have plenty of server programes on my linux).
Is it possible to clone my RedHat9 linux to another HDD?
If possible, how?

Thanks

Mount another HDD say under /mnt/imagehd

and type

dd if=/dev/hda of=/mnt/imagehd/rh9image

where /dev/hda is the location of the HDD you want to image.

To restore you would need to boot the system (or a Linux rescue disc) and mount the hdd with the image on it (perhaps in the same place)
and do

dd if=/mnt/imagehd/rh9image of=/dev/hda

again, where /dev/hda is the HDD you want to restore to

This will produce a full image of the hard drive and will overwrite everything on the hard drive when you restore.

Instead of mount a new HDD, can I make the image file into a new created folder (for example /home/user/image), and through the network copy to another machine this image file?
dd if=/dev/hda of=/home/user/image/rh9image
Restore:
If the above mentioned process possible, then the restore process:
At first I would copy the image file to another HDD and the restore process is the same as you said
dd if=/mnt/imagehd/rh9image of=/dev/hda

Im pretty much sure that wouldnt work because what DD is doing is creating a bit-by-bit image of your HDD and putting it somewhere else and you cant have stuff updating on your HDD or itll end up corrupted.

Is there any program like ghost, to clone entire linux HDD?

dd does the same thing as Ghost. Ghost is simply a friendly front end for a low-level routine similar to dd.

Of course, you can use Ghost to clone ANY harddisk....

Look up netcat and dd to clone a system over the network. If you want to ghost the machine, g4u is pretty popular.

-twantrd

I cloned my linux HDD with dd command yesterday, but I have some problems.
My linux HDD has the following partitions:
Device Boot Start End Blocks ID System
/dev/hda1 * 1 13 10439 83 Linux
/dev/hda2 14 9954 79851082+ 83 Linux
/dev/hda3 9955 10011 457852+ 82 Linux swap

First I shuted down my linux os and connected a HDD with the same parameters as my linux HDD. After that I switched on the system. The new HDD became /dev/hdc. After that I type the command:
dd if=/dev/hda of=/dev/hdc
and a couple of hours later I get the message that copying is successfully completed (or something similar). After that my second hdc had completely the same partitions as my primary HDD:

Device Boot Start End Blocks ID System
/dev/hdc1 * 1 13 10439 83 Linux
/dev/hdc2 14 9954 79851082+ 83 Linux
/dev/hdc3 9955 10011 457852+ 82 Linux swap

So I thinked that if I disconnected my primary (Linux) HDD, and I started machine with secondary HDD it would work, but unfortunately not. If I start machine with clone HDD, I get the command "Kernel panic".
Why?