/usr/share/xsessions/xterm.desktop is in gdm 3.0.4-0ubuntu15.
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 9 | [Desktop Entry]
Encoding=UTF-8
Name=Recovery Console
Comment=Failsafe session with only xterm
Exec=xterm
TryExec=xterm
Icon=
Type=Application
X-Ubuntu-Gettext-Domain=gdm
|