/usr/share/xsessions/ubuntu-2d.desktop is in gnome-session 3.2.1-0ubuntu8.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 | [Desktop Entry]
Name=Ubuntu 2D
Comment=This session logs you into Ubuntu 2D Mode
Exec=gnome-session --session=ubuntu-2d
TryExec=unity-2d-panel
Icon=
Type=Application
X-Ubuntu-Gettext-Domain=gnome-session-3.0
|