Hi Aaron.
I would step back into the operation of yum a bit first. On a CentOS system I had to manually add a repo file first (per http://docs.mongodb.org/manual/tutorial/install-mongodb-on-red-hat-centos-or-fedora-linux/). But it looks like you did that perfectly already.
So just to check yum does have the repo in it's repolist:
[root@ip-172-31-2-127 ~]# yum repolist Loaded plugins: fastestmirror, security Loading mirror speeds from cached hostfile * base: centos.nsw.au.glomirror.com.au * extras: centos.mirror.uber.com.au * updates: centos.nsw.au.glomirror.com.au repo id repo name status base CentOS-6 - Base 6,518 cr CentOS-6 - CR 0 extras CentOS-6 - Extras 36 mongodb MongoDB Repository 250 updates CentOS-6 - Updates 710 repolist: 7,514
If mongodb repo is there, then the following package name search should find something.
[root@ip-172-31-2-127 ~]# yum search mongodb-org Loaded plugins: fastestmirror, security Loading mirror speeds from cached hostfile * base: centos.mirror.digitalpacific.com.au * extras: centos.mirror.uber.com.au * updates: centos.mirror.uber.com.au =================== N/S Matched: mongodb =================== mongodb-org.x86_64 : MongoDB cross-platform document-oriented database system : (metapackage) mongodb-org-mongos.x86_64 : MongoDB sharding router mongodb-org-server.x86_64 : MongoDB database server .... ....
And alternative to the search above would be to yum list | grep '\bmongodb\s*$' to see all packages found in the repo.
If those succeed I can't think of any other reason why "yum install mongodb-org" would give a "No package <X> available." message.
Cheers,
Akira
(P.S. it would be helpful to know the CentOS version you have.)