I just upgraded to 14.04, I had no error messages but Unity disappeared from the list of desktop environments in the log in screen. As you can see below, Unity is installed. How can I log in back again with Unity?
$ dpkg -l | grep unity
ii gir1.2-unity-5.0:amd64 7.1.4+14.04.20140210-0ubuntu1 amd64 GObject introspection data for the Unity library
ii gnome-themes-ubuntu 0.6.1 all Ubuntu community themes
ii libmeanwhile1 1.0.2-4.1ubuntu1 amd64 open implementation of the Lotus Sametime Community Client protocol
ii libunity-2d-private0 7.2.0+14.04.20140423-0ubuntu1.2 all transitional dummy package
rc libunity-action-qt1:amd64 1.1.0+14.04.20140304-0ubuntu1 amd64 Unity Action Qt API
ii libunity-control-center1 14.04.3+14.04.20140410-0ubuntu1 amd64 utilities to configure the GNOME desktop
rc libunity-core-5.0-5 5.20.0-0ubuntu3 amd64 Core library for the Unity interface.
ii libunity-core-6.0-9 7.2.0+14.04.20140423-0ubuntu1.2 amd64 core library for the Unity interface
ii libunity-gtk2-parser0:amd64 0.0.0+14.04.20140403-0ubuntu1 amd64 GtkMenuShell to GMenuModel parser
ii libunity-gtk3-parser0:amd64 0.0.0+14.04.20140403-0ubuntu1 amd64 GtkMenuShell to GMenuModel parser
ii libunity-misc4 4.0.5+14.04.20140115-0ubuntu1 amd64 Miscellaneous functions for Unity - shared library
ii libunity-protocol-private0:amd64 7.1.4+14.04.20140210-0ubuntu1 amd64 binding to get places into the launcher - private library
ii libunity-scopes-json-def-desktop 7.1.4+14.04.20140210-0ubuntu1 all binding to get places into the launcher - desktop def file
ii libunity9:amd64 7.1.4+14.04.20140210-0ubuntu1 amd64 binding to get places into the launcher - shared library
ii libunityvoice1:amd64 0.1+14.04.20140304-0ubuntu1 amd64 client library for Unity voice service
ii unity 7.2.0+14.04.20140423-0ubuntu1.2 amd64 Interface designed for efficiency of space and interaction.
ii unity-2d 7.2.0+14.04.20140423-0ubuntu1.2 all transitional dummy package
ii unity-2d-common 7.2.0+14.04.20140423-0ubuntu1.2 all transitional dummy package
ii unity-2d-panel 7.2.0+14.04.20140423-0ubuntu1.2 all transitional dummy package
ii unity-2d-shell 7.2.0+14.04.20140423-0ubuntu1.2 all transitional dummy package
ii unity-2d-spread 7.2.0+14.04.20140423-0ubuntu1.2 all transitional dummy package
ii unity-asset-pool 0.8.24daily13.06.10-0ubuntu1 all Unity Assets Pool
rc unity-common 5.20.0-0ubuntu3 all Common files for the Unity interface.
ii unity-control-center 14.04.3+14.04.20140410-0ubuntu1 amd64 utilities to configure the GNOME desktop
ii unity-control-center-signon 0.1.7~+14.04.20140211.2-0ubuntu4 amd64 Unity Control Center extension for single signon
ii unity-greeter 14.04.9-0ubuntu1 amd64 Unity Greeter
ii unity-gtk-module-common 0.0.0+14.04.20140403-0ubuntu1 all Common files for GtkMenuShell D-Bus exporter
ii unity-gtk2-module:amd64 0.0.0+14.04.20140403-0ubuntu1 amd64 GtkMenuShell D-Bus exporter
ii unity-gtk3-module:amd64 0.0.0+14.04.20140403-0ubuntu1 amd64 GtkMenuShell D-Bus exporter
ii unity-lens-applications 7.1.0+13.10.20131011-0ubuntu2 amd64 Application lens for unity
ii unity-lens-files 7.1.0+13.10.20130920-0ubuntu1 amd64 File lens for unity
ii unity-lens-friends 0.1.3+14.04.20140317-0ubuntu1 amd64 Friends scope for unity
ii unity-lens-music 6.9.0+13.10.20131011-0ubuntu1 amd64 Music lens for unity
ii unity-lens-photos 1.0+14.04.20140318-0ubuntu1 all Photos lens for Unity
ii unity-lens-video 0.3.15+13.10.20130920-0ubuntu1 amd64 Unity Video lens
ii unity-scope-audacious 0.1+13.10.20130927.1-0ubuntu1 all Audacious scope for Unity
ii unity-scope-calculator 0.1+14.04.20140328-0ubuntu1 all Calculator scope for Unity
ii unity-scope-chromiumbookmarks 0.1+13.10.20130723-0ubuntu1 all Chromium bookmarks scope for Unity
ii unity-scope-clementine 0.1+13.10.20130723-0ubuntu1 all Clementine scope for Unity
ii unity-scope-colourlovers 0.1+13.10.20130723-0ubuntu1 all COLOURlovers scope for Unity
ii unity-scope-devhelp 0.1+14.04.20140328-0ubuntu1 all devhelp scope for Unity
ii unity-scope-firefoxbookmarks 0.1+13.10.20130809.1-0ubuntu1 all Firefox bookmarks scope for Unity
ii unity-scope-gdrive 0.9+13.10.20130723-0ubuntu1 all Google Drive scope for Unity
ii unity-scope-gmusicbrowser 0.1+13.10.20130723-0ubuntu1 all gmusicbrowser scope for Unity
ii unity-scope-gourmet 0.1+13.10.20130723-0ubuntu1 all Gourmet Recipe Manager scope for Unity
ii unity-scope-guayadeque 0.1+13.10.20130927.1-0ubuntu1 all Guayadeque scope for Unity
ii unity-scope-home 6.8.2+14.04.20131029.1-0ubuntu1 amd64 Home scope that aggregates results from multiple scopes
ii unity-scope-manpages 3.0+14.04.20140324-0ubuntu1 all Manual pages scope for Unity
ii unity-scope-musicstores 6.9.0+13.10.20131011-0ubuntu1 amd64 Ubuntu One music store scope for unity
ii unity-scope-musique 0.1+13.10.20130723-0ubuntu1 all Musique scope for Unity
ii unity-scope-openclipart 0.1+13.10.20130723-0ubuntu1 all OpenClipArt scope for Unity
ii unity-scope-texdoc 0.1+14.04.20140328-0ubuntu1 all Texdoc scope for Unity
ii unity-scope-tomboy 0.1+13.10.20130723-0ubuntu1 all Tomboy scope for Unity
ii unity-scope-video-remote 0.3.15+13.10.20130920-0ubuntu1 amd64 Remote videos engine
ii unity-scope-virtualbox 0.1+13.10.20130723-0ubuntu1 all VirtualBox scope for Unity
ii unity-scope-yelp 0.1+13.10.20130723-0ubuntu1 all Help scope for Unity
ii unity-scope-zotero 0.1+13.10.20130723-0ubuntu1 all Zotero scope for Unity
ii unity-scopes-master-default 6.8.2+14.04.20131029.1-0ubuntu1 all Home scope that aggregates results from multiple scopes
ii unity-scopes-runner 7.1.4+14.04.20140210-0ubuntu1 all desktop runner for misceallenous scopes
ii unity-services 7.2.0+14.04.20140423-0ubuntu1.2 amd64 Services for the Unity interface
ii unity-settings-daemon 14.04.0+14.04.20140414-0ubuntu1 amd64 daemon handling the Unity session settings
ii unity-voice-service:amd64 0.1+14.04.20140304-0ubuntu1 amd64 Voice recognition service for unity
ii xubuntu-community-wallpapers 14.04.0 all Xubuntu community wallpapers
