about ubuntu 14.04

someone can provide me a ubuntu 14.04 image file?

The TK1 and TX1 had Ubuntu 14.04 in their early days. The TX2 arrived after 16.04 was already in use, so I don’t believe there is any officially supported version 14.04 on a TX2. A new release of L4T R28.1 (Ubuntu 16.04) came out yesterday and may resolve some issues on the old 16.04 release, but you’d probably have to port your own 14.04 version.