Running Centos 6.5, I updated my mongod to 2.6.4 and upon start mongod via /etc/init.d/mongod I get the following error:

ERROR: child process failed, exited with error number 14

I noticed that the init script requires numactl but the numactl package is not installed on my system.

init.d-mongd: https://github.com/mongodb/mongo/blob/master/rpm/init.d-mongod
rpm spec: https://github.com/mongodb/mongo/blob/master/rpm/mongodb-org.spec

I installed numactl and I solved the problem.

This affects 2.6.4 up to the latest version.

Adding numactl to the specs' Requires line should solve this problem...