Instructions for setting up mongo server on Amazon EC2 instance with CentOS(x86_64)

mongo_install_instructions.txt

nano /etc/yum.repos.d/mongodb.repo

Paste the following code in this file:
[mongodb]
name=MongoDB Repository
baseurl=http://downloads-distro.mongodb.org/repo/redhat/os/x86_64/
gpgcheck=0
enabled=1

yum install mongo-10gen mongo-10gen-server

service mongod start

If you get error in the above command as command service not found, create an alias:
alias service="/sbin/service"

Now change the mongodb directory to /mnt since it requires a lot of space:
service mongod stop
mkdir /mnt/mongo
nano /etc/mongod.conf

change the dbpath variable with /mnt/mongo

chwon mongod /mnt/mongo

service mongod start

Lastly install gems so that the ruby script runs:
gem install mongo bson_ext

Check by starting the mongo shell with `mongo` command

References:
[1] http://docs.mongodb.org/manual/tutorial/install-mongodb-on-red-hat-centos-or-fedora-linux/
[2] http://docs.mongodb.org/manual/tutorial/install-mongodb-on-linux/
[3] http://www.flaviogambardella.com/ruby-on-rails/configure-rails-to-use-mongodb-without-mongomapper/

See [3] for using mongodb with rails