I can't startx in my Ubuntu
 

startxs works fine before,I don't know what got it corrupted.And when I typing it now,i will get this:
mktemp:failed to create file via template '/tmp/serverauth.XXXXXXXXXX':Not a directory
xauth:creating new authority file
xauth:unable to link authority file,use -n
xauth:creating new authority file
xauth:unable to link authority file,use -n
xauth:creating new authority file
xauth:unable to link authority file,use -n

X:cannot stat /tmp/.X11-unix(Not a directory),aborting.
giving up.
xinit:Not a directory (errno 20):unable to connect to X server
xinit:No such process(errno 3):Server error.

How can I change the black screen into GUI?
Ctr+Alt+F7 is also useless.the prompt likes:
init:mounted-tmp main process(690)terminated with status 2 mountall:Event failed

Every reply is appreciate!

Seems you have an issue related to your /tmp folder. Did you put it in a seperate partition or change the access rights of that folder? Can you ls -la and see what access there is on your /tmp?

Did you move your temporary folder location somehow?

Thank you very much!That's my problem.I deleted '\tmp' directory in my program and forgot to mkdir a new one.