步骤如下：

1.更新原有系统

sudo apt-get update
sudo apt-get upgrade

更改源

vim /etc/apt/sources.list

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运行命令

do-release-upgrade

如果提示如下：

-bash: do-release-upgrade: command not found

则输入如下命令安装所需软件：

sudo apt-get update
sudo apt-get install update-manager-core

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