How to retrieve Cluster ID / JobFlow ID from EMR master node.

You may look at  /mnt/var/lib/info/ on Master node to find lot of info about your EMR cluster setup.

More specifically /mnt/var/lib/info/job-flow.json contains the jobFlowId or ClusterID.

I was able to install a JSON parser on my Master node to retrieve jobFlowID.

# Install JSON PARSER
# Install pkgs required for jsawk 
wget http://pkgs.repoforge.org/js/js-1.60-1.el6.rf.x86_64.rpm 
wget http://pkgs.repoforge.org/js/js-devel-1.60-1.el6.rf.x86_64.rpm 
sudo yum install -y js-1.60-1.el6.rf.x86_64.rpm 
sudo yum install -y js-devel-1.60-1.el6.rf.x86_64.rpm
# Install JSAWK curl -L http://github.com/micha/jsawk/raw/master/jsawk > jsawk
chmod 755 jsawk && sudo mv jsawk /usr/bin/
# Parse and print job flow ID 
jsawk 'return this.jobFlowId' < /mnt/var/lib/info/job-flow.json