On https://docs.mongodb.com/manual/tutorial/install-mongodb-on-os-x/#run-mongodb, we're a bit terse about the steps necessary to grant the appropriate permissions to the /data/db folder in order for the mongod process to properly run.

In some cases, the current user is not necessarily super admin of his own MacOS machine and would have to run

sudo mkdir /data/db to get the db folder created.

In this situation, permissions need to be manually set as well for the mongod process to run properly.

I've found that the following command line worked for me, is there a way you could mention it in our OSX setup docs as a suggestion, at least? (in case the user wants to run the mongod process with the identity of the current user)

sudo chown -R `id -un` /data/db