What are the differences between gnome, gnome-shell and gnome-core?

I am running Ubuntu GNOME and apt says that I have gnome-shell installed, but not gnome or gnome-core.

$ apt-cache policy gnome
gnome:
  Installed: (none)
  Candidate: 1:3.8+4ubuntu3
  Version table:
     1:3.8+4ubuntu3 0
        500 http://in.archive.ubuntu.com/ubuntu/ trusty/universe i386 Packages

$ apt-cache policy gnome-shell
gnome-shell:
  Installed: 3.10.4-0ubuntu5
  Candidate: 3.10.4-0ubuntu5
  Version table:
 *** 3.10.4-0ubuntu5 0
        500 http://in.archive.ubuntu.com/ubuntu/ trusty/universe i386 Packages
        100 /var/lib/dpkg/status

$ apt-cache policy gnome-core
gnome-core:
  Installed: (none)
  Candidate: 1:3.8+4ubuntu3
  Version table:
     1:3.8+4ubuntu3 0
        500 http://in.archive.ubuntu.com/ubuntu/ trusty/universe i386 Packages

Why does apt say I have not installed gnome, although I'm using GNOME as the desktop environment?

Solution 1:

This is just an issue of metapackages. The Debian world (and I believe the RedHat one as well) has collected certain programs that are used together into easy-to-install metapackages. So, the package gnome is actually a shortcut for installing all sorts of goodies:

aisleriot, alacarte, avahi-daemon, cheese, cups-pk-helper, desktop-base, evolution, evolution-plugins, file-roller, gedit, gedit-plugins, gimp, gnome-applets, gnome-color-manager, gnome-core, gnome-documents, gnome-games, gnome-media, gnome-nettool, gnome-orca, gnome-shell-extensions, gnome-tweak-tool, gstreamer1.0-libav, gstreamer1.0-plugins-ugly, hamster-applet, inkscape, libgtk2-perl, libreoffice-calc, libreoffice-gnome, libreoffice-impress, libreoffice-writer, nautilus-sendto, network-manager-gnome, rhythmbox, rhythmbox-plugin-cdrecorder, rhythmbox-plugins, rygel-playbin, rygel-preferences, rygel-tracker, seahorse, shotwell, simple-scan, sound-juicer, telepathy-gabble, telepathy-rakia, telepathy-salut, tomboy, totem, totem-plugins, tracker-gui, transmission-gtk, vinagre, xdg-user-dirs-gtk, browser-plugin-gnash, gdebi, nautilus-sendto-empathy, telepathy-idle, dia-gnome, gnome-boxes, gnucash, libreoffice-evolution, planner

This is the full Gnome desktop and is not needed to run the Gnome desktop environment. So, while you have gnome-shell installed, you don't have all the associated applications like games and email client etc that come with the full desktop environment.

This is not a problem and it does not hinder you from using Gnome in any way.

gnome-core is also a meta package, it will install the official "core" modules of the Gnome desktop:

at-spi2-core, baobab, brasero, caribou, caribou-antler, dconf-gsettings-backend, dconf-tools, empathy, eog, evince, evolution-data-server, firefox, or, fonts-cantarell, gconf2, gdm, gkbd-capplet, glib-networking, gnome-backgrounds, gnome-bluetooth, gnome-calculator, gnome-contacts, gnome-control-center, gnome-dictionary, gnome-disk-utility, gnome-font-viewer, gnome-icon-theme, gnome-icon-theme-extras, gnome-icon-theme-symbolic, gnome-keyring, gnome-menus, gnome-online-accounts, gnome-packagekit, gnome-panel, gnome-power-manager, gnome-screensaver, gnome-screenshot, gnome-session, gnome-settings-daemon, gnome-shell, gnome-sushi, gnome-system-log, gnome-system-monitor, gnome-terminal, gnome-themes-standard, gnome-user-guide, gnome-user-share, gsettings-desktop-schemas, gstreamer1.0-plugins-base, gstreamer1.0-plugins-good, gstreamer1.0-pulseaudio, gtk2-engines, gucharmap, gvfs-backends, gvfs-bin, libatk-adaptor, libcanberra-pulse, libcaribou-gtk-module, libcaribou-gtk3-module, libgtk-3-common, libpam-gnome-keyring, metacity, mousetweaks, nautilus, notification-daemon, pulseaudio, sound-theme-freedesktop, tracker-gui, vino, yelp, zenity, network-manager-gnome, gnome,

Note that the gnome metapackage also installs the gnome-core metapackage. In any case, the main point here is that metapackages are not needed. You can install each of their component packages manually so lacking one or more metapackages does not imply that anything is actually missing from your system.