How to upgrade Wheezy to Jessie ???

This probably a dumb question, but how do I upgrade Wheezy to Jessie without losing any data?
I have onwcloud, proftpd, and samba on my pi.

Thanks

Your DietPi image is configured for Wheezy. If you upgrade using apt-get dist-upgrade, you will break most of DietPi’s functions. This is mainly due to system services (LSB to SystemD).

Your best bet would be to backup your current data, then write the DietPi Jessie image which is configured for Jessie.
You can use one of DietPi’s file servers to pull your data off. https://dietpi.com/forum/t/setup-guide-accessing-files-on-your-dietpi-system/28/1

i see
thank you very much.