I am trying to change the data directory used by bitcoind and I am uder the impression that the command -datadir was removed as I can't find it with bitcoin-cli help, when I try to use it I get Too few parameters and bitcoin-cli help datadir says datadir doesn't exist. I need to specify a directory that is not on the root partition, how to do it ?

Also why bitcoin core is so user unfriendly, it's quite surprising I thought it was the main bitcoin program. It started downloading the blockchain on my root partition without me even being aware of it (just start bitcoind and it starts silently downloading).