在此过程中，sudo apt-get autoremove我意外删除了 ubuntu-desktop。已安装 KDE，但出于不同原因（unity - 工作，kde - 上网）想切换它们。因此，在尝试安装 ubuntu-desktop 时，我得到了以下输出：
tukanoid@tukanoid-Inspiron-5545:~$ sudo apt-get install ubuntu-desktop
[sudo] password for tukanoid:
Reading package lists... Done
Building dependency tree
Reading state information... 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:
ubuntu-desktop : Depends: checkbox-gui but it is not going to be installed
Recommends: python3-aptdaemon.pkcompat but it is not going to be installed
Recommends: unity-webapps-common but it is not going to be installed
E: Unable to correct problems, you have held broken packages.
尝试执行sudo apt-get -f install有此输出：
tukanoid@tukanoid-Inspiron-5545:~$ sudo apt-get -f install
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following package was automatically installed and is no longer required:
linux-image-extra-4.4.0-53-generic
Use 'sudo apt autoremove' to remove it.
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
之后sudo dpkg --configure -a什么都没发生。我也尝试通过 安装 ubuntu-desktop，aptitude但是我收到了这条消息，我真的不喜欢它：
tukanoid@tukanoid-Inspiron-5545:~$ sudo aptitude install ubuntu-desktop
The following NEW packages will be installed:
checkbox-converged{a} checkbox-gui{a} liboxideqt-qmlplugin{a} liboxideqtcore0{ab}
liboxideqtquick0{a} libqt5organizer5{ab} libubuntugestures5{ab} libubuntutoolkit5{ab}
libunity-webapps0{a} python3-aptdaemon.pkcompat{ab} qml-module-ubuntu-components{ab}
qml-module-ubuntu-layouts{ab} qml-module-ubuntu-test{ab} qml-module-ubuntu-web{a}
qtdeclarative5-ubuntu-ui-toolkit-plugin{a} ubuntu-desktop unity-webapps-common{a}
unity-webapps-qml{a} unity-webapps-service{a} webapp-container{ab} webbrowser-app{ab}
0 packages upgraded, 21 newly installed, 0 to remove and 0 not upgraded.
Need to get 34.1 MB/35.0 MB of archives. After unpacking 138 MB will be used.
The following packages have unmet dependencies:
"Many packages, that are installed"
The following actions will resolve these dependencies:
Keep the following packages at their current version:
1) checkbox-converged [Not Installed]
2) checkbox-gui [Not Installed]
3) liboxideqt-qmlplugin [Not Installed]
4) liboxideqtcore0 [Not Installed]
5) liboxideqtquick0 [Not Installed]
6) libqt5organizer5 [Not Installed]
7) libubuntugestures5 [Not Installed]
8) libubuntutoolkit5 [Not Installed]
9) libunity-webapps0 [Not Installed]
10) python3-aptdaemon.pkcompat [Not Installed]
11) qml-module-ubuntu-components [Not Installed]
12) qml-module-ubuntu-layouts [Not Installed]
13) qml-module-ubuntu-test [Not Installed]
14) qml-module-ubuntu-web [Not Installed]
15) qtdeclarative5-ubuntu-ui-toolkit-plugin [Not Installed]
16) ubuntu-desktop [Not Installed]
17) unity-webapps-common [Not Installed]
18) unity-webapps-qml [Not Installed]
19) unity-webapps-service [Not Installed]
20) webapp-container [Not Installed]
21) webbrowser-app [Not Installed]
Accept this solution? [Y/n/q/?]
最后sudo apt-get install qtbase-abi-5-5-1我得到：
tukanoid@tukanoid-Inspiron-5545:~$ sudo apt-get install qtbase-abi-5-5-1
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package qtbase-abi-5-5-1 is a virtual package provided by:
libqt5core5a 5.5.1+dfsg-16ubuntu7.2 [Not candidate version]
libqt5core5a 5.5.1+dfsg-16ubuntu7 [Not candidate version]
E: Package 'qtbase-abi-5-5-1' has no installation candidate
答案1
你可能删除了Ubuntu PPA而不降级其他软件包。为此，请再次添加并执行：
sudo apt-get install ppa-purge
sudo ppa-purge ppa:kubuntu-ppa/backports