Remove Kubuntu:

sudo apt-get remove akonadi-backend-mysql akonadi-server akregator amarok amarok-common amarok-utils apport-kde apturl-kde ark bluedevil cdparanoia cdrdao cryptsetup docbook-xml docbook-xsl dolphin dragonplayer freespacenotifier gnupg-agent gnupg2 gpgsm gpsd gstreamer0.10-qapt gtk2-engines-oxygen gtk3-engines-oxygen gwenview ibus-qt4 icoutils jockey-kde k3b k3b-data kaccessible kaddressbook kamera kate kate-data katepart kcalc kde-baseapps-bin kde-baseapps-data kde-config-gtk kde-config-touchpad 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 kde-zeroconf kdegames-card-data kdegraphics-strigi-analyzer kdelibs-bin kdelibs5-data kdelibs5-plugins kdemultimedia-kio-plugins kdenetwork-filesharing kdepasswd kdepim-kresources kdepim-runtime kdepim-strigi-plugins kdepimlibs-kio-plugins kdesudo kdm kdoctools khelpcenter4 kinfocenter klipper kmag kmail kmenuedit kmix kmousetool knotes konsole kontact kopete kopete-message-indicator korganizer kpat kppp ksnapshot ksysguard ksysguardd ksystemlog ktimetracker ktorrent ktorrent-data kubuntu-debug-installer kubuntu-default-settings kubuntu-desktop kubuntu-docs kubuntu-firefox-installer kubuntu-netbook-default-settings kubuntu-notification-helper kubuntu-web-shortcuts kvkbd kwalletmanager language-selector-kde libakonadi-calendar4 libakonadi-contact4 libakonadi-kabc4 libakonadi-kcal4 libakonadi-kde4 libakonadi-kmime4 libakonadi-notes4 libakonadiprotocolinternals1 libassuan0 libattica0.3 libbluedevil1 libboost-program-options1.46.1 libcalendarsupport4 libcln6 libclucene0ldbl libdebconf-kde0 libdlrestrictions1 libdmtx0a libencode-locale-perl libepub0 libeventviews4 libfile-listing-perl libflac++6 libfont-afm-perl libgadu3 libgif4 libgpgme++2 libgps20 libgrantlee-core0 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 libibus-qt1 libilmbase6 libincidenceeditorsng4 libindicate-qt1 libio-socket-inet6-perl libio-socket-ssl-perl libk3b6 libkabc4 libkactivities-bin libkactivities6 libkalarmcal2 libkateinterfaces4 libkatepartinterfaces4 libkblog4 libkcal4 libkcalcore4 libkcalutils4 libkcddb4 libkcmutils4 libkde3support4 libkdeclarative5 libkdecorations4 libkdecore5 libkdegames5a libkdepim4 libkdepimdbusinterfaces4 libkdesu5 libkdeui5 libkdewebkit5 libkdgantt2 libkdnssd4 libkemoticons4 libkephal4abi1 libkexiv2-10 libkexiv2-data libkfile4 libkholidays4 libkhtml5 libkidletime4 libkimap4 libkio5 libkipi-data libkipi8 libkjsapi4 libkjsembed4 libkldap4 libkleo4 libkmanagesieve4 libkmbox4 libkmediaplayer4 libkmime4 libknewstuff2-4 libknewstuff3-4 libknotifyconfig4 libkntlm4 libkonq-common libkonq5-templates libkonq5abi1 libkontactinterface4 libkopete4 libkparts4 libkpgp4 libkpimidentities4 libkpimtextedit4 libkpimutils4 libkprintutils4 libkpty4 libkresources4 libkrosscore4 libksba8 libkscreensaver5 libksgrd4 libksieve4 libksieveui4 libksignalplotter4 libktexteditor4 libktnef4 libktorrent-l10n libktorrent3 libkunitconversion4 libkwineffects1abi3 libkwinglutils1 libkwinnvidiahack4 libkworkspace4abi1 libkxmlrpcclient4 liblastfm0 libloudmouth1-0 liblwp-mediatypes-perl liblwp-protocol-https-perl libmailcommon4 libmailtools-perl libmailtransport4 libmessagecomposer4 libmessagecore4 libmessagelist4 libmessageviewer4 libmicroblog4 libmpcdec6 libmsn0.3 libmuonprivate1 libmygpo-qt1 libmysqlclient18 libnepomuk4 libnepomukdatamanagement4 libnepomukquery4a libnepomuksync4 libnepomukutils4 libnet-http-perl libnet-ssleay-perl libntrack-qt4-1 libntrack0 libokularcore1abi1 libopenexr6 libotr2 libphonon4 libplasma-geolocation-interface4 libplasma3 libplasmaclock4abi3 libplasmagenericshell4 libpolkit-qt-1-1 libpoppler-qt4-3 libprison0 libprocesscore4abi1 libprocessui4a libqalculate5 libqapt-runtime libqapt1 libqca2 libqca2-plugin-ossl libqgpgme1 libqimageblitz4 libqjson0 libqrencode3 libqt4-designer libqt4-help libqt4-qt3support libqt4-scripttools libqt4-sql-mysql libqt4-test libqtassistantclient4 libqtglib-2.0-0 libqtgstreamer-0.10-0 libqtscript4-core libqtscript4-gui libqtscript4-network libqtscript4-sql libqtscript4-uitools libqtscript4-xml libqtwebkit4 libreoffice-kde libreoffice-style-oxygen libsocket6-perl libsolid4 libsolidcontrol4abi2 libsolidcontrolifaces4abi2 libsoprano4 libstreamanalyzer0 libstreams0 libsyndication4 libtag-extras1 libtaskmanager4abi3 libtemplateparser4 libthreadweaver4 libtimedate-perl liburi-perl libvirtodbc0 libweather-ion6 libwww-perl libwww-robotrules-perl libxml2-utils libxss1 libzip2 muon muon-installer muon-notifier muon-updater mysql-client-core-5.5 mysql-common mysql-server-core-5.5 ntrack-module-libnl-0 odbcinst odbcinst1debian2 okular okular-extra-backends oxygen-cursor-theme oxygen-icon-theme partitionmanager phonon phonon-backend-gstreamer pinentry-gtk2 pinentry-qt4 plasma-dataengines-addons plasma-dataengines-workspace plasma-desktop plasma-netbook plasma-scriptengine-javascript plasma-scriptengine-python plasma-widget-facebook plasma-widget-folderview plasma-widget-kimpanel plasma-widget-menubar plasma-widget-message-indicator plasma-widget-networkmanagement plasma-widgets-addons plasma-widgets-workspace plymouth-theme-kubuntu-logo plymouth-theme-kubuntu-text polkit-kde-1 printer-applet python-kde4 python-pyudev python-qt4 python-qt4-dbus python-sip qapt-batch qapt-deb-installer quassel quassel-data rekonq sgml-data shared-desktop-ontologies software-properties-kde soprano-daemon system-config-printer-kde systemsettings tasks-icons update-manager-kde usb-creator-kde userconfig virtuoso-minimal virtuoso-opensource-6.1-bin virtuoso-opensource-6.1-common xsettings-kde && sudo apt-get install ubuntu-desktop

Remove Xubuntu:

sudo apt-get remove abiword abiword-common abiword-plugin-grammar abiword-plugin-mathview alacarte bison blueman brltty-x11 catfish docbook-xml exo-utils flex fonts-droid gigolo gimp gimp-data gmusicbrowser gnome-desktop-data gnome-system-tools gnome-time-admin gnumeric gnumeric-common gnumeric-doc gstreamer0.10-gnomevfs gthumb gthumb-data gtk2-engines-pixbuf indicator-application-gtk2 indicator-messages-gtk2 indicator-sound-gtk2 indicator-status-provider-pidgin leafpad libabiword-2.9 libao-common libao4 libaudio-scrobbler-perl libbabl-0.0-0 libbison-dev libcolamd2.7.1 libconfig-inifiles-perl libdigest-crc-perl libencode-locale-perl libept1.4.12 libexo-1-0 libexo-common libexo-helpers libfile-listing-perl libfl-dev libfont-afm-perl libgarcon-1-0 libgarcon-common libgdome2-0 libgdome2-cpp-smart0c2a libgegl-0.0-0 libgimp2.0 libglade2-0 libgnomevfs2-0 libgnomevfs2-common libgnomevfs2-extra libgoffice-0.8-8 libgoffice-0.8-8-common libgsf-1-114 libgsf-1-common libgstreamer-perl libgtk2-notify-perl libgtk2-trayicon-perl libgtkmathview0c2a libgtkspell0 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 libid3tag0 libido-0.1-0 libilmbase6 libio-socket-inet6-perl libio-socket-ssl-perl libjavascriptcoregtk-1.0-0 libjpeg-progs libjpeg-turbo-progs libkeybinder0 liblaunchpad-integration1 liblink-grammar4 libloudmouth1-0 liblwp-mediatypes-perl liblwp-protocol-https-perl libmad0 libmailtools-perl libnet-dbus-perl libnet-http-perl libnet-ssleay-perl liboobs-1-5 libopenexr6 libotr2 libots0 librarian0 libsexy2 libsocket6-perl libtagc0 libthunarx-2-0 libtidy-0.99-0 libtie-ixhash-perl libtimedate-perl libtumbler-1-0 libunique-1.0-0 liburi-perl libvte-common libvte9 libwebkitgtk-1.0-0 libwebkitgtk-1.0-common libwv-1.2-4 libwww-perl libwww-robotrules-perl libxfce4ui-1-0 libxfce4util-bin libxfce4util-common libxfce4util4 libxfcegui4-4 libxfconf-0-2 libxml-parser-perl libxml-twig-perl libxml-xpath-perl libxss1 lightdm-gtk-greeter link-grammar-dictionaries-en linux-headers-3.2.0-24 linux-headers-3.2.0-24-generic linux-headers-generic lp-solve m4 mpg321 orage parole pastebinit pavucontrol pidgin pidgin-data pidgin-libnotify pidgin-microblog pidgin-otr plymouth-theme-xubuntu-logo plymouth-theme-xubuntu-text python-configobj python-glade2 python-gmenu rarian-compat ristretto screensaver-default-images sgml-data shimmer-themes synaptic system-tools-backends tcl8.5 thunar thunar-archive-plugin thunar-data thunar-media-tags-plugin thunar-volman ttf-droid ttf-lyx tumbler tumbler-common xchat xchat-common xfburn xfce-keyboard-shortcuts xfce4-appfinder xfce4-cpugraph-plugin xfce4-datetime-plugin xfce4-dict xfce4-indicator-plugin xfce4-mailwatch-plugin xfce4-netload-plugin xfce4-notes xfce4-notes-plugin xfce4-notifyd xfce4-panel xfce4-places-plugin xfce4-power-manager xfce4-power-manager-data xfce4-quicklauncher-plugin xfce4-screenshooter xfce4-session xfce4-settings xfce4-systemload-plugin xfce4-taskmanager xfce4-terminal xfce4-utils xfce4-verve-plugin xfce4-volumed xfce4-weather-plugin xfce4-xkb-plugin xfconf xfdesktop4 xfdesktop4-data xfwm4 xscreensaver xscreensaver-data xscreensaver-gl xubuntu-artwork xubuntu-default-settings xubuntu-desktop xubuntu-docs xubuntu-icon-theme xubuntu-wallpapers && sudo apt-get install ubuntu-desktop && sudo /usr/lib/lightdm/lightdm-set-defaults -g unity-greeter

Remove Lubuntu:

sudo apt-get remove abiword abiword-common abiword-plugin-grammar abiword-plugin-mathview ace-of-penguins audacious audacious-plugins audacious-plugins-data blueman chromium-browser chromium-browser-l10n chromium-codecs-ffmpeg docbook-xml elementary-icon-theme esound-common galculator gdebi gdebi-core gecko-mediaplayer giblib1 gnome-desktop-data gnome-icon-theme-full gnome-mplayer gnome-system-tools gnome-time-admin gnumeric gnumeric-common gnumeric-doc gpicview gtk2-engines-pixbuf guvcview hardinfo indicator-status-provider-pidgin leafpad libaacs0 libabiword-2.9 libass4 libaudclient2 libaudcore1 libaudiofile1 libavcodec53 libavformat53 libavutil51 libbinio1ldbl libbluray1 libbs2b0 libcddb2 libcolamd2.7.1 libcompfaceg1 libcue1 libdca0 libdirectfb-1.2-9 libdvdnav4 libdvdread4 libenca0 libencode-locale-perl libept1.4.12 libesd0 libexo-1-0 libexo-common libexo-helpers libfaad2 libfile-listing-perl libfluidsynth1 libfm-data libfm-gtk-data libfm-gtk1 libfm1 libfont-afm-perl libgdome2-0 libgdome2-cpp-smart0c2a libgif4 libglade2-0 libgmlib0 libgmtk0 libgmtk0-data libgoffice-0.8-8 libgoffice-0.8-8-common libgringotts2 libgsf-1-114 libgsf-1-common libgsm1 libgtkmathview0c2a libgtkspell0 libguess1 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 libid3tag0 libimlib2 libio-socket-inet6-perl libio-socket-ssl-perl libjavascriptcoregtk-1.0-0 libjpeg-progs libjpeg-turbo-progs liblaunchpad-integration1 liblink-grammar4 libloudmouth1-0 liblwp-mediatypes-perl liblwp-protocol-https-perl libmailtools-perl libmcrypt4 libmenu-cache1 libmms0 libmodplug1 libmowgli2 libmp3lame0 libmpg123-0 libnet-dbus-perl libnet-http-perl libnet-ssleay-perl libnss3-1d libobrender27 libobt0 libonig2 liboobs-1-5 libopts25 libots0 libpisock9 libpostproc52 librarian0 libresid-builder0c2a libschroedinger-1.0-0 libsidplay2 libsocket6-perl libswscale2 libtar0 libtidy-0.99-0 libtie-ixhash-perl libtimedate-perl libts-0.0-0 libuniconf4.6 liburi-perl libva1 libvdpau1 libvpx1 libvte-common libvte9 libwebcam0 libwebkitgtk-1.0-0 libwebkitgtk-1.0-common libwv-1.2-4 libwvstreams4.6-base libwvstreams4.6-extras libwww-perl libwww-robotrules-perl libxfce4ui-1-0 libxfce4util-bin libxfce4util-common libxfce4util4 libxfconf-0-2 libxml-parser-perl libxml-twig-perl libxml-xpath-perl libxss1 libxvidcore4 lightdm-gtk-greeter link-grammar-dictionaries-en linux-headers-3.2.0-24 linux-headers-3.2.0-24-generic linux-headers-generic lm-sensors lp-solve lubuntu-artwork lubuntu-artwork-12-04 lubuntu-core lubuntu-default-settings lubuntu-desktop lubuntu-icon-theme lubuntu-software-center lxappearance lxappearance-obconf lxinput lxkeymap lxlauncher lxmenu-data lxpanel lxpanel-indicator-applet-plugin lxrandr lxsession lxsession-edit lxshortcut lxtask lxterminal mplayer2 mtpaint ntp obconf openbox openbox-themes osmo pcmanfm pidgin pidgin-data pidgin-libnotify pidgin-microblog plymouth-theme-lubuntu-logo plymouth-theme-lubuntu-text python-pysqlite2 python-support python-xklavier rarian-compat scrot sgml-data sylpheed sylpheed-doc sylpheed-i18n sylpheed-plugins synaptic system-tools-backends transmission tsconf ttf-lyx uvcdynctrl uvcdynctrl-data wvdial xfburn xfce-keyboard-shortcuts xfce4-power-manager xfce4-power-manager-data xfconf xfonts-100dpi xpad xscreensaver xscreensaver-data && sudo apt-get install ubuntu-desktop && sudo /usr/lib/lightdm/lightdm-set-defaults -g unity-greeter

以上备忘