总结
尽管我仍在使用 xenial，但系统认为应该下载 bionic 的软件包。我无法从 xenial 升级到 bionic，因为我应该先升级所有可用的软件包。当我尝试这样做时，它会下载 bionic 软件包然后中止，因为操作系统版本与新软件包版本不匹配。我怎样才能告诉我的系统它仍然是 xenial 而不是 bionic？
我开始运行 ubuntu 升级程序，如上所述本网站。 所以：
sudo apt update
sudo apt upgrade
sudo apt dist-upgrade
sudo apt autoremove
sudo apt autoclean
然后开始运行升级程序（确认我已经安装了update-manager-core）
sudo do-release-upgrade
一切都按预期进行。到目前为止还不错。它问我是否要按“y”或“N”继续，还是按“d”查看详细信息。为了好玩，我按了“d”和“enter”。我在终端中查看详细信息。好的，这一切都很有趣。无论如何。到达终点后，它向我显示
(END)
我应该在这里停下来，打开这个网站，而不是做一些愚蠢的事情。我按下“enter”，什么也没发生，“escape”什么也没发生，“backspace”什么也没发生。然后我选择按下“Ctrl+C”，升级程序中止，我回到之前的终端内容，但没有提示。我尝试“y”继续升级发行版，但失败了。好吧，关闭终端，重新打开它，再试sudo do-release-upgrade一次。出了点问题，但我不记得当时是什么问题了。无论如何，我重新启动了整个系统，打开了终端，现在我们在这里：
thymaro@ultra:~$ sudo do-release-upgrade
Checking for a new Ubuntu release
Please install all available updates for your release before upgrading.
thymaro@ultra:~$ sudo apt-get update
Hit:1 http://it-mirrors.evowise.com/ubuntu bionic InRelease
Hit:2 http://it-mirrors.evowise.com/ubuntu bionic-updates InRelease
Hit:3 http://archive.canonical.com/ubuntu bionic InRelease
Hit:4 http://it-mirrors.evowise.com/ubuntu bionic-backports InRelease
Hit:5 http://it-mirrors.evowise.com/ubuntu bionic-security InRelease
Reading package lists... Done
thymaro@ultra:~$ sudo apt-get -y dist-upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
The following packages were automatically installed and are no longer required:
account-plugin-facebook account-plugin-flickr account-plugin-google
.... {list of hundreds more packages}
Use 'sudo apt autoremove' to remove them.
The following packages will be REMOVED:
checkbox-converged checkbox-gui curl gir1.2-totem-plparser-1.0
.... {list of dozens more packages}
The following NEW packages will be installed:
apache2-bin autopoint binutils-common binutils-x86-64-linux-gnu bolt
.... {list of hundreds more packages}
The following packages will be upgraded:
a11y-profile-manager-indicator accountsservice acl acpid
.... {list of hundreds more packages}
2355 to upgrade, 615 to newly install, 77 to remove and 0 not to upgrade.
Need to get 1'505 MB/2'207 MB of archives.
After this operation, 2'269 MB of additional disk space will be used.
Get:1 http://it-mirrors.evowise.com/ubuntu bionic-updates/main amd64 libglvnd0 amd64 1.0.0-2ubuntu2.3 [47.0 kB]
Get:2 http://it-mirrors.evowise.com/ubuntu bionic-updates/main amd64 libwayland-egl1-mesa amd64 19.2.8-0ubuntu0~18.04.3 [6'892 B]
Get:3 http://it-mirrors.evowise.com/ubuntu bionic-updates/main amd64 libwayland-egl1 amd64 1.16.0-1ubuntu1.1~18.04.3 [5'464 B]
Get:4 http://it-mirrors.evowise.com/ubuntu bionic-updates/main amd64 libqt5dbus5 amd64 5.9.5+dfsg-0ubuntu2.5 [195 kB]
... {about a thousand more lines downloading 'bionic' packages}
问题位于 tl;dr 下的帖子开头。
答案1
该do-release-upgrade命令会改变您的来源。
要更改您的来源：
编辑 /etc/apt/sources.list（需要 sudo）。
sudoedit /etc/apt/sources.list // CLI //OR// sudo -H gedit /etc/apt/sources.list // GUI仔细检查每一行：将写有“bionic”的每一行改回“xenial”。
完成并保存后，运行 sudo apt update。