I apparently have a redis-server instance running because when I try to start a new server by entering redis-server, I'm greeted with the following:

Opening port: bind: Address already in use

I can't figure out how to stop this server and start a new one.

Is there any command I can append to redis-server when I'm typing in the CLI?

My OS is Ubuntu 10.04.

Either connect to node instance and use shutdown command or if you are on ubuntu you can try to restart redis server through init.d:

/etc/init.d/redis-server restart

or stop/start it:

/etc/init.d/redis-server stop
/etc/init.d/redis-server start

On Mac

redis-cli shutdown