Version Update in Ubuntu.

1) From upgrading from 8.04 and 9.10 to latest LTS (10.04).

Check the current version by cat /etc/issue

Run apt-get update

Upgrade the current installations to latest release in the current version, for that Run apt-get upgrade

Set the upgrade file to check for latest LTS version, for that set PROMPT=lts in /etc/update-manager/release-upgrades

Then perform the upgrade by running d0-release-upgrade

This will update the OS version to latest LTS version.

Confirm by checking /etc/issue

Upgrade procedure for the versions in which the direct upgrade will not work (Eg : 9.04 to 10.04)

Check the current version by cat /etc/issue

Run apt-get update

Upgrade the current installations to latest release in the current version, for that Run apt-get upgrade

Then comes the tricky step, Edit the /etc/apt/sources.list file and replace the current repo name with the repo to which you need to be upgraded. In the case of 9.04 to 10.04 updgrade replace jaunty with lucid and save the file.

Then run apt-get update and apt-get upgrade

This will update the ubuntu to the new version.

Enjoy and have a nice time with ubuntu :)