Server
First become root:
sudo su
Then run
apt-get update
and install the package update-manager-core:
apt-get install update-manager-core
Open the file /etc/update-manager/release-upgrades...
vi /etc/update-manager/release-upgrades
... and make sure it has Prompt=normal in it:
[...]
Prompt=normal
Then run
do-release-upgrade
to start the distribution upgrade.
root@server1:~# do-release-upgrade
Checking for a new ubuntu release
Done Upgrade tool signature
Done Upgrade tool
Done downloading
extracting 'jaunty.tar.gz'
authenticate 'jaunty.tar.gz' against 'jaunty.tar.gz.gpg'
Reading cache
Checking package manager
Continue running under SSH?
This session appears to be running under ssh. It is not recommended
to perform a upgrade over ssh currently because in case of failure it
is harder to recover.
If you continue, a additional ssh daemon will be started at port
'9004'.
Do you want to continue?
Continue [yN] <-- y
Confirm that you want to do the upgrade:
Calculating the changes
Do you want to start the upgrade?
1 package is going to be removed. 29 new packages are going to be
installed. 392 packages are going to be upgraded.
You have to download a total of 236M. This download will take about 2
minutes with your connection.
Fetching and installing the upgrade can take several hours. Once the
download has finished, the process cannot be cancelled.
Continue [yN] Details [d] <-- y
At the end of the upgrade process, you should remove obsolete packages:
Remove obsolete packages?
28 packages are going to be removed.
Continue [yN] Details [d] <-- y
The server needs to be rebooted to complete the upgrade:
System upgrade is complete.
Restart required
To finish the upgrade, a restart is required.
If you select 'y' the system will be restarted.
Continue [yN] <-- y
After the reboot, your server is running Ubuntu 9.04.
ที่มา
http://www.howtoforge.com/how-to-upgrade-ubuntu-8.10-to-ubuntu-9.04-desktop-and-server