hello
I want to upgrade my ubuntu 10.04 to 10.10 or 11.04 but I afraid of doing that because last time that I did it upgraded successfully but after restarting, it went to blank screen and I forced to install a new UBUNTU. unfortunately there was no other previous version of UBUNTU in boot option.My question is how can I update or upgrade my UBUNTU to another one with keeping all of last versions data(kernel,modules,drivers,....)that if new version does not recognize some thing I have other choice to boot my system from ubuntu boot menu.

Thank you very much.

You can't. The meaning of upgrade is to replace older versions with newer ones. If you want to have a safe way to upgrade you have two options:
- Install the new version alongside the old one, so that you have two different installs.
- Make a full system backup and then upgrade. If something goes wrong you can easily restore your backup.

My personal opinion: Ubuntu 10.04 is a long term support (LTS) version. If you don't have the need for a specific newer version of a software don't do an upgrade, especially because 11.04 seems to be rather buggy.

Install side-by-side as a "dual boot," each version on its own separate partition.

but I thing you two are wrong because I did it before in fedora 8 . I mean I had two options when I upgraded my system from internet, one with previous kernel one with new one but I don't know what fedora did because it did it automatically .

Of course you will be able to boot the old kernel. That is one of the few components that will not be replaced. The rest of the system will.

One way to achieve your goal would be to use btrfs or lvm and create a snapshot before updating. Then if all goes wrong you can restore the snapshot.

You will need to do some research about your booting options. I'm not sure if grub2 can boot from btrfs or a lvm volume, if so you should be ok, if not you need to make sure the upgrade doesn't delete your old kernel.

Ubuntu does not offer the option using the upgrade. And two or three or four or ... kernels is not the same as an upgrade. Ubuntu keeps kernels during updates.

Long ago when I set up my main desktop, I kept a spare partition to install newer versions. I've however never used it.

My advise is not to upgrade but do a fresh install. Download the iso, testdrive it in live mode to check if the Ubuntu idiots did not screw something up and next install it. My upgrade from 8.04 to 10.04 went awfully wrong, and just like you I ended up doing a fresh install at the end anyway.

And I also suggest that you stick with the LTS releases unless you need functionality in a program that is not provided by the current version in the repository of that program.