Says Process Completed and the pc closes unexpectedly.

[rashbip]

~ $ ubuntu
ubuntu@localhost:~$ vncstart

Warning: localhost.localdomain:1 is taken because of /tmp/.X11-unix/X1
Remove this file if there is no X server localhost.localdomain:1

Warning: localhost.localdomain:1 is taken because of /tmp/.X1-lock
Remove this file if there is no X server localhost.localdomain:1

Warning: localhost.localdomain:2 is taken because of /tmp/.X11-unix/X2
Remove this file if there is no X server localhost.localdomain:2

Warning: localhost.localdomain:2 is taken because of /tmp/.X2-lock
Remove this file if there is no X server localhost.localdomain:2

Warning: localhost.localdomain:3 is taken because of /tmp/.X11-unix/X3
Remove this file if there is no X server localhost.localdomain:3

Warning: localhost.localdomain:3 is taken because of /tmp/.X3-lock
Remove this file if there is no X server localhost.localdomain:3

New Xtigervnc server 'localhost.localdomain:4 (ubuntu)' on port 5904 for display :4.
Use xtigervncviewer -SecurityTypes VncAuth -passwd /tmp/tigervnc.Tb17VQ/passwd :4 to connect to the VNC server.

ubuntu@localhost:~$
[Process completed (signal 9) - press Enter]