最新的Ubuntu LTS版本Ubuntu 18.04（Bionic Beaver）于2016年4月26日发布，它将受支持5年，直到2023年4月。
在本教程中，我们将向我们展示如何升级Ubuntu 16.04安装或者更高版本。
到Ubuntu 18.04（Bionic Beaver）。

准备工作

在开始本教程之前，请确保我们以具有sudo特权的用户身份登录。

备份资料

首先，请确保在开始操作系统的重大升级之前先备份数据。
如果我们在虚拟机上运行Ubuntu，则最好进行完整的系统快照，以便在更新进行到南方时可以轻松地还原计算机。

更新当前安装的软件包

在开始版本升级之前，建议将所有当前安装的软件包更新为最新版本。

sudo apt updatesudo apt upgrade

我们还将运行'dist-upgrade'，它将对已安装的软件包进行主要版本升级，并可能删除一些不必要的软件包：

sudo apt dist-upgrade

将Ubuntu 16.04升级到Ubuntu 18.04

Ubuntu提供了一个名为“ do-release-upgrade”的工具，该工具使升级过程变得非常简单。

该工具应该已经安装在系统上，但是如果由于某种原因未安装该工具，则可以使用以下工具进行安装：

sudo apt install update-manager-core

要开始升级，请运行'do-release-upgrade'：

sudo do-release-upgrade

如果要像我一样通过SSH升级系统，系统将询问我们是否要继续。

Reading cache
Checking package manager
Continue running under SSH?
This session appears to be running under ssh. It is not recommended
to perform an 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.
If you run a firewall, you Jan need to temporarily open this port. As
this is potentially dangerous it's not done automatically. You can
open the port with e.g.:
'iptables -I INPUT -p tcp --dport 1022 -j ACCEPT'
To continue please press [ENTER]

升级工具下载软件包列表并计算更改后，它将询问我们是否要继续。

Do you want to start the upgrade?
4 installed packages are no longer supported by Canonical. You can
still get support from the community.
3 packages are going to be removed. 90 new packages are going to be
installed. 397 packages are going to be upgraded.
You have to download a total of 267 M. This download will take about
1 minute with your connection.
Installing the upgrade can take several hours. Once the download has
finished, the process cannot be canceled.

再次输入“ y”，升级过程将开始。

在升级过程中，系统将询问我们各种问题，例如我们是要保留现有的配置文件还是要安装软件包维护者的版本。
如果我们未对文件进行任何自定义更改，则可以安全地键入“ Y”，否则要保持当前配置，请输入“ N”。

Configuration file '/etc/sysctl.conf'
 ==> Modified (by you or by a script) since installation.
 ==> Package distributor has shipped an updated version.
   What would you like to do about it ?  Your options are:
    Y or I  : install the package maintainer's version
    N or O  : keep your currently-installed version
      D     : show the differences between the versions
      Z     : start a shell to examine the situation
 The default action is to keep your current version.
*** sysctl.conf (Y/I/N/O/D/Z) [default=N] ?

升级过程可能需要一些时间，具体取决于更新的数量和Internet速度。

一旦安装了新软件包，更新工具将询问我们是否要删除过时的软件，如果不确定是否键入'd'并检查过时的软件包列表，在大多数情况下可以安全地输入'y'并删除所有过时的软件包：

Searching for obsolete software
Reading package lists... Done
Building dependency tree
Reading state information... Done
Reading state information... Done
Remove obsolete packages?

17 packages are going to be removed.

升级过程完成并假设一切顺利后，系统将要求我们重新启动计算机。
输入“ y”继续：

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

确认更新

等待片刻，直到服务器重新启动，然后重新连接。
登录后，我们会收到以下消息：

Welcome to Ubuntu 18.04 LTS (GNU/Linux 4.15.0-20-generic x86_64)

我们还可以使用以下命令检查Ubuntu版本：

lsb_release -a

No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 18.04 LTS
Release:    18.04
Codename:   bionic

我们现在可以享受新的Ubuntu 18.04 LTS（Bionic Beaver）。