These instructions are for Ubuntu 12.04 running the Unity desktop on which kde-plasma-desktop was installed using either the Ubuntu Software Center or sudo apt-get on the command line.

The instructions may be the same for other versions of Ubuntu, but no guarantee is made.

When kde-plasma-desktop is installed in Ubuntu 12.04, it installs several packages and libraries it requires as well as some optional packages. Not all these packages and libraries are uninstalled when you uninstall kde-plasma-desktop. Several packages (like dolphin and kwrite) do not get uninstalled.

Quick Uninstall

This is not recommended because it will remove all packages normally installed with kde-plasma-desktop. This may include packages you previously installed (like dolphin or kwrite) or packages previously installed by other applications.

Note: this uninstall command assumes kde-plasma-desktop was installed on a fresh Ubuntu 12.04.

1) Open a terminal (instructions can be found here).

2) Enter the following command (it is very long and a single line):

sudo apt-get purge --auto-remove akonadi-backend-mysql akonadi-server docbook-xsl dolphin freespacenotifier gpsd  icoutils kate-data katepart kde-baseapps kde-baseapps-bin kde-baseapps-data  kde-plasma-desktop kde-runtime kde-runtime-data kde-style-oxygen  kde-wallpapers-default kde-window-manager kde-window-manager-common  kde-workspace kde-workspace-bin kde-workspace-data kde-workspace-kgreet-plugins  kdelibs-bin kdelibs5-data kdelibs5-plugins kdepasswd kdepim-runtime  kdepimlibs-kio-plugins kdm kdoctools kfind kinfocenter klipper kmenuedit  konqueror konqueror-nsplugins konsole ksysguard ksysguardd  kubuntu-debug-installer kwrite libakonadi-calendar4 libakonadi-contact4  libakonadi-kabc4 libakonadi-kcal4 libakonadi-kde4 libakonadi-kmime4  libakonadi-notes4 libakonadiprotocolinternals1 libattica0.3  libboost-program-options1.46.1 libcln6 libclucene0ldbl libdlrestrictions1  libdmtx0a libencode-locale-perl libfile-listing-perl libfont-afm-perl libgps20  libhtml-form-perl libhtml-format-perl libhtml-parser-perl libhtml-tagset-perl  libhtml-tree-perl libhttp-cookies-perl libhttp-daemon-perl libhttp-date-perl  libhttp-message-perl libhttp-negotiate-perl libilmbase6 libio-socket-inet6-perl  libio-socket-ssl-perl libkabc4 libkactivities-bin libkactivities6 libkalarmcal2  libkatepartinterfaces4 libkcal4 libkcalcore4 libkcalutils4 libkcmutils4  libkde3support4 libkdeclarative5 libkdecorations4 libkdecore5 libkdesu5  libkdeui5 libkdewebkit5 libkdnssd4 libkemoticons4 libkephal4abi1 libkfile4  libkholidays4 libkhtml5 libkidletime4 libkimap4 libkio5 libkjsapi4 libkjsembed4  libkldap4 libkmbox4 libkmediaplayer4 libkmime4 libknewstuff3-4 libknotifyconfig4  libkntlm4 libkonq-common libkonq5-templates libkonq5abi1 libkonqsidebarplugin4a  libkparts4 libkpimidentities4 libkpimtextedit4 libkpimutils4 libkpty4  libkresources4 libkrosscore4 libkscreensaver5 libksgrd4 libksignalplotter4  libktexteditor4 libkunitconversion4 libkwineffects1abi3 libkwinglutils1  libkwinnvidiahack4 libkworkspace4abi1 liblwp-mediatypes-perl  liblwp-protocol-https-perl libmailtools-perl libmailtransport4 libmicroblog4  libnepomuk4 libnepomukdatamanagement4 libnepomukquery4a libnepomuksync4  libnepomukutils4 libnet-http-perl libnet-ssleay-perl libntrack-qt4-1 libntrack0  libopenexr6 libphonon4 libplasma-geolocation-interface4 libplasma3  libplasmaclock4abi3 libplasmagenericshell4 libpolkit-qt-1-1 libprison0  libprocesscore4abi1 libprocessui4a libqalculate5 libqapt-runtime libqapt1  libqca2 libqimageblitz4 libqrencode3 libqt4-qt3support libsocket6-perl libsolid4  libsolidcontrol4abi2 libsolidcontrolifaces4abi2 libsoprano4 libstreamanalyzer0  libstreams0 libsyndication4 libtaskmanager4abi3 libthreadweaver4  libtimedate-perl liburi-perl libvirtodbc0 libweather-ion6 libwww-perl  libwww-robotrules-perl libxml2-utils libxss1 mysql-client-core-5.5  mysql-server-core-5.5 ntrack-module-libnl-0 odbcinst odbcinst1debian2  oxygen-cursor-theme oxygen-icon-theme phonon phonon-backend-gstreamer  plasma-dataengines-workspace plasma-desktop plasma-scriptengine-javascript  plasma-widget-folderview plasma-widgets-workspace qapt-batch  shared-desktop-ontologies soprano-daemon systemsettings virtuoso-minimal  virtuoso-opensource-6.1-bin virtuoso-opensource-6.1-common

It is easiest to copy the line and paste it into the terminal (right-click on the terminal and select Paste from the popup menu).

Preferred Uninstall

The better way to uninstall it is to follow the directions on this page.

This will show you on how to uninstall only the packages that were installed when kde-plasma-desktop was installed. The instructions are generic and work for any installed package.

It involves:

identifying which packages were installed and
creating a command to uninstall only those packages

It leaves intact any packages you may have installed (like dolphin or kwrite) or that were installed by other packages instead of blindly assuming that they were installed along with kde-plasma-desktop.