[vagrant@meteor vagrant]$ ls
microscope  Vagrantfile
[vagrant@meteor vagrant]$ cd microscope/
[vagrant@meteor microscope]$ cd .meteor/
[vagrant@meteor .meteor]$ cd local/
[vagrant@meteor local]$ ls
db
[vagrant@meteor local]$ ln -s ~/db/
ln: creating symbolic link `./db': File exists
[vagrant@meteor local]$ ls -la
total 0
drwxrwxrwx 1 vagrant vagrant 0 Apr  3 19:30 .
drwxrwxrwx 1 vagrant vagrant 0 Apr  3 19:30 ..
drwxrwxrwx 1 vagrant vagrant 0 Apr  3 19:30 db
[vagrant@meteor local]$ cd ../../
[vagrant@meteor microscope]$ meteor
[[[[[ /vagrant/microscope ]]]]]

=> Started proxy.
Unexpected mongo exit code 100. Restarting.
Unexpected mongo exit code 100. Restarting.
Unexpected mongo exit code 100. Restarting.
Can't start Mongo server.
MongoDB had an unspecified uncaught exception.
This can be caused by MongoDB being unable to write to a local database.
Check that you have permissions to write to .meteor/local. MongoDB does
not support filesystems like NFS that do not allow file locking.
[vagrant@meteor microscope]$