主要内容：Ubuntu 11.10桌面版与服务器版升级到Ubuntu 12.04 LTS。
桌面版本Ubuntu 11.10升级到Ubuntu 12.04 LTS只需要启动更新管理器，然后更新管理器中就出现新的版本，选择最新的版本进行更新，然后就按基本的要求进行下去即可完成升级。
服务器版本升级到Ubuntu 12.04 LTS
1.首先成为root用户
sudo su
2.然后运行
apt-get update
3.然后安装最新的更新
apt-get upgrade
4.安装更新包的核心
apt-get install update-manager-core
5.打开文件/etc/update-manager/release-upgrades
vi /etc/update-manager/release-upgrades
6.看是否提示正常
[...]
Prompt=normal
7.然后运行
do-release-upgrade
8.开始升级
root@server1:~# do-release-upgrade
Checking for a new ubuntu release
Get:1 Upgrade tool signature [198 B]
Get:2 Upgrade tool [1550 kB]
Fetched 1550 kB in 0s (0 B/s)
authenticate "precise.tar.gz" against "precise.tar.gz.gpg"
extracting "precise.tar.gz"
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, an additional ssh daemon will be started at port
"1022".
Do you want to continue?
Continue [yN]
Starting additional sshd
To make recovery in case of failure easier, an additional sshd will be started on port "1022". If anything goes wrong with the running ssh you can still connect to the additional one.
To continue please press [ENTER]
[...]
Do you want to start the upgrade?
2 installed packages are no longer supported by Canonical. You can
still get support from the community.
5 packages are going to be removed. 52 new packages are going to be
installed. 426 packages are going to be upgraded.
You have to download a total of 286 M. This download will take about
2 minutes with your connection.
Installing the upgrade can take several hours. Once the download has finished, the process cannot be canceled.
Continue [yN] Details [d]
在更新过程中，一些服务可能需要重新启动。如果更新管理问你哪些服务应该重新启动(它显示了一个服务列表)，只接受按默认服务输入。
在升级过程结束时，应该删除过时的包：
Remove obsolete packages?
19 packages are going to be removed.
Continue [yN] Details [d]
服务器需要重新启动才能完成升级：
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]
重新启动后，可以肯定的是您的服务器正在运行的Ubuntu 12.04。来/ etc / issue中看看：
cat /etc/issue
root@server1:~# cat /etc/issue
Ubuntu 12.04 LTS \n \l
root@server1:~#
这样服务器版本就升级完毕了，从上面的过程可以看出，其实直接升级相对直接安装还是非常简单的，而且需要的时间也相对较少，而且也省去了相应的配置，但是升级系统容易出现错误，引起系统不能重启，大家可以根据需要，自行决定安装方法，Ubuntu 12.04 LTS服务器版本还是值得大家尝试的。