我尝试从 Ubuntu 20.04 升级到 21.04，但没有成功。我首先运行下列的：
sudo apt update
sudo apt dist-upgrade
sudo shutdown -r now
重启后，我仍然有 20.04。我尝试手动从软件和更新，它显示有可用的升级
但当我按下 OK 时，没有其他窗口出现。在终端上我得到：
$ sudo apt update
Hit:1 https://download.docker.com/linux/ubuntu focal InRelease
Hit:2 http://ppa.launchpad.net/alexlarsson/flatpak/ubuntu focal InRelease
Hit:3 http://de.archive.ubuntu.com/ubuntu focal InRelease
Hit:4 http://dl.google.com/linux/chrome/deb stable InRelease
Hit:5 https://linux.teamviewer.com/deb stable InRelease
Hit:6 http://ppa.launchpad.net/eugenesan/ppa/ubuntu focal InRelease
Get:7 http://de.archive.ubuntu.com/ubuntu focal-updates InRelease [114 kB]
Hit:9 https://cloud.r-project.org/bin/linux/ubuntu focal-cran40/ InRelease
Hit:10 http://ppa.launchpad.net/libreoffice/ppa/ubuntu focal InRelease
Hit:11 https://packages.microsoft.com/repos/ms-teams stable InRelease
Hit:12 http://security.ubuntu.com/ubuntu focal-security InRelease
Hit:13 http://ppa.launchpad.net/linuxuprising/java/ubuntu focal InRelease
Get:14 http://de.archive.ubuntu.com/ubuntu focal-backports InRelease [101 kB]
Hit:15 http://apt.insync.io/ubuntu focal InRelease
Hit:16 http://ppa.launchpad.net/smathot/cogscinl/ubuntu focal InRelease
Hit:17 https://linux-clients.seafile.com/seafile-deb/focal stable InRelease
Hit:8 https://github.com/retorquere/zotero-deb/releases/download/apt-get ./ InRelease
Fetched 214 kB in 3s (68.1 kB/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done
5 packages can be upgraded. Run 'apt list --upgradable' to see them.
$ apt list --upgradable
Listing... Done
libboost-date-time-dev/focal 1.71.0.0ubuntu2 amd64 [upgradable from: 1.67.0.2]
libboost-filesystem-dev/focal 1.71.0.0ubuntu2 amd64 [upgradable from: 1.67.0.2]
libboost-iostreams-dev/focal 1.71.0.0ubuntu2 amd64 [upgradable from: 1.67.0.2]
libboost-program-options-dev/focal 1.71.0.0ubuntu2 amd64 [upgradable from: 1.67.0.2]
libboost-system-dev/focal 1.71.0.0ubuntu2 amd64 [upgradable from: 1.67.0.2]
$ sudo apt upgrade libboost-system-dev/focal
Reading package lists... Done
Building dependency tree
Reading state information... Done
Selected version '1.71.0.0ubuntu2' (Ubuntu:20.04/focal [amd64]) for 'libboost-system-dev'
Calculating upgrade... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies.
libboost-system-dev : Depends: libboost-system1.71-dev but it is not going to be installed
E: Broken packages
$ sudo apt upgrade libboost-system-dev
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies.
libboost-system-dev : Depends: libboost-system1.71-dev but it is not going to be installed
E: Broken packages
$ do-release-upgrade
Checking for a new Ubuntu release
Please install all available updates for your release before upgrading.
问题可能出在哪里？我该如何解决？我应该删除这些仍处于待处理状态的文件吗？我应该使用什么命令？
谢谢