The exadata db nodes have a factory image which contains a limited set of rpms. You have to install custom rpms after the initial installation/delivery yourself.
If you install custom rpms you might run into dependency issues later when doing firmware updates (see 1473002.1 section: Conflicting RPM's).
For instance for every firmware update (4 times / year) you might have to:
De-install conflicting rpms.
Upgrade the db node.
Re-install the custom rpms.
You should be able to install the extra X11 rpms from the below directory
/opt/oracle.SupportTools/onecommand/option_rpms => cd basic_X_and_vncserver
/opt/oracle.SupportTools/onecommand/option_rpms/basic_X_and_vncserver => ls
chkfontpath-1.10.1-1.1.x86_64.rpm libXfontcache-1.0.2-3.1.x86_64.rpm xorg-x11-fonts-base-7.1-2.1.el5.noarch.rpm xterm-215-8.el5_4.1.x86_64.rpm
install.sh libXTrap-1.0.0-3.1.x86_64.rpm xorg-x11-font-utils-7.1-2.x86_64.rpm
libfontenc-1.0.2-2.2.el5.x86_64.rpm README.txt xorg-x11-server-utils-7.1-4.fc6.x86_64.rpm
libXfont-1.2.2-1.0.3.el5_1.x86_64.rpm vnc-server-4.1.2-14.el5_3.1.x86_64.rpm xorg-x11-twm-1.0.1-3.1.x86_64.rpm
[oracle@dm58db01:]/opt/oracle.SupportTools/onecommand/option_rpms/basic_X_and_vncserver => cat install.sh
ls -1 | grep -iq chkfontpath
if [ $? -eq 0 ]; then
rpm -Uhv --nodeps *.rpm
echo "[ERROR] You must run $0 from the directory where it exists along with the rest of the X and vncserver rpms."
As part of the install the ACS resource hardens the environment at the end of the build
Hope that helps