How to define createdate of entire image folder using terminal with exiftool?

I have folder containing images. I have to rename them according to their date n all. But when I used

$ exiftool '-filename<CreateDate' -d %y%m%d_%H%M%S%%-c.%%le -r /home/ubuntu/houseWarning: No writable tags set from /home/ubuntu/house/120151116163735582.jpg

And when i used

$ exiftool '-FileName<${CreateDate}_${Exif:Model}.jpg' -d %Y%m%d_%H%M%S-%%2c *  Warning: [minor] Tag 'CreateDate' not defined - 120151116163715535.jpgWarning: No writable tags set from 120151116163715535.jpg