Startup: Unable to open [/data/db/mongodb.log] for log file: errno: 13 Permission denied

I cannot start mongodb in ubuntu 10.04 lucid in linode.

I am following this tutorial http://library.linode.com/databases/mongodb/ubuntu-10.04-lucid#sph_id4 but when I try to run the commands:

/etc/init.d/mongodb start /etc/init.d/mongodb stop

I am getting the error:

Starting : can't open [/data/db/mongodb.log] for log file: errno:13 Permission denied

      

        
        
        
      

    

How can I fix this?

Thank!