My first full node - no bitcoin.conf So I am in the process of downloading the blocks after installing bitcoin on my ubuntu server. I have followed the guide on https://bitcoin.org/en/full-node.

Everything is working correctly. Blocks are downloading just fine to ~/.bitcoin/blocks. bitcoin-cli commands are working without error. 

If I switch users and I try to issue a bitcoin-cli command naturally I get "Could not locate RPC credentials. No authentication cookie could be found, and RPC password is not set."

However when using the correct user where cli commands do work, there is still no bitcoin.conf file inside ~/.bitcoin/ As the node is downloading the blocks and the cli commands work I assume there must be a conf file - yet its not where every single document and support answer claims it will be. 

I have tried find . -name "bitcoin.conf" in the ~/.bitcoin directory as well as user ~/ and in /etc all return empty. Where else could this file possibly hide? If it doesn't exists why would I still be downloading blocks and able to issue cli commands?

I am aware this question has been asked countless times but i cant find any answers relating to the fact the node is working and cli commands are working.
When you don't explicitly specify any RPC credentials, bitcoind will autogenerate them for you and store the password in the $DATADIR/.cookie file.

You can then use the username __cookie__ along with the password from that file.