How can I tell where mongoDB is storing data? (its not in the default /data/db!)

My host came with a mongodb instance and there is no /db directory so now I am wondering what I can do to find out where the data is actually being stored.

mongod defaults the database location to /data/db/.

If you run ps -xa | grep mongod and you don't see a --dbpath which explicitly tells mongod to look at that parameter for the db location and you don't have a dbpath in your mongodb.conf, then the default location will be: /data/db/ and you should look there.

What does your configuration file say?

$ grep dbpath /etc/mongodb.conf

If it is not correct, try this, your database files will be present on the list:

$ sudo lsof -p `ps aux | grep mongodb | head -n1 | tr -s ' ' | cut -d' ' -f 2` | grep REG

It's /var/lib/mongodb/* on my default installation (Ubuntu 11.04).

Note that there is also a /var/lib/mongodb/mongod.lock file holding mongod PID for convenience, however it is located in the data directory - which we are looking for...

I find db.serverCmdLineOpts() the most robust way to find actual path if you can connect to the server. The "parsed.storage.dbPath" contains the path your server is currently using and is available both when it's taken from the config or from the command line arguments.

Also in my case it was important to make sure that the config value reflects the actual value (i.e. config didn't change after the last restart), which isn't guaranteed by the solutions offered here.

db.serverCmdLineOpts()

Example output:

{
    "argv" : [ 
        // --
    ],
    "parsed" : {
        "config" : "/your-config",
        "storage" : {
            "dbPath" : "/your/actual/db/path",
            // --
        }
    },
    "ok" : 1.0
}

In the newer version of mongodb v2.6.4 try:

grep dbpath /etc/mongod.conf

It will give you something like this:

dbpath=/var/lib/mongodb

And that is where it stores the data.

While this question is targeted for Linux/Unix instances of Mongo, it's one of the first search results regardless of the operating system used, so for future Windows users that find this:

If MongoDB is set up as a Windows Service in the default manner, you can usually find it by looking at the 'Path to executable' entry in the MongoDB Service's Properties: