Is there a way to update from 2.6x to 2.9x via the command line?

I want to update/upgrade from 2.6x to last release in the 2.9.x. I do NOT want to go to V3.(OTA update only provides the v3 option)
Is there a way to do this from the command line? if so, how?

Will it erase my existing connections to my music sources, play lists etc? if so, how to preserve & restore?

I am running volumio on a RPi 3b+
Thank you!