Lucid Lynx is packed with Features and promises. Upgrading your Karmic Koala to Lucid Lynx makes more sense than ever. And certainly its damn easy to do it.
Method 1. (Needs Internet) via Update manager
Step 1. Start the Update Manager (System > Administration > Update Manager):
Step 2. The Update Manager should show that a new distribution release (10.04 LTS) is available. Click the Upgrade button to start the distribution upgrade
Method 2. Offline Upgrade (no Internet required)
This method is much faster since it uses offline ISO image to upgrade from HERE.
Step 1. Let’s go ahead and Mount the image
sudo mount -o loop /path-to-iso/ubuntu-10.04-alternate-i386.iso /media/cdrom0
Step 2. When success, a pop up should appear offering you the option to upgrade using that CD / ISO image.
If for some reason the upgrade dialog doesn’t pop-up, press ALT + F2 and type:
gksu "sh /cdrom/cdromupgrade"
kdesudo "sh /cdrom/cdromupgrade"
[iso credits: ParaIso]