I recently added, using Ambari, a new compute node to my cluster. How can I do a sanity check and make sure it's got the same configuration as the other compute nodes?
Ambari should manage this already depending on the clients/services installed. And if there is no refresh icon, it will be up-to-date.
Feel free to spot-check the configurations for your services in /usr/hdp/current/ or /etc/hadoop/conf
By default, Ambari pushes all service configuration (identified as default configuration group) to any newly added node. If you want to make changes for a particular node then you need to go create a different config group for that node. But, if you still want to compare then the best way to compare is: to download config for the new node and for an old node from Ambari UI and compare them using linux (diff command) or any third party comparison tool/editor.
The best way is to check the config group of that host, if that belongs to the same as of others then configurations are same.
Usually all hosts belongs to "default" config groups only by default but if you want to change something for a particular host you can override that and make a new config group.