If you get this warning when you connect to mongo shell in Mac OX X:
** WARNING: soft rlimits too low. Number of files is 256, should be at least 1000
You can increase that limit by just running this on the Mac OS X shell:
launchctl limit maxfiles 1024 1024
This other command has the same effect but it will only last until the next system reboot:
ulimit -n 1024
Restart mongod
and it shouldn’t complain any more.