[chef] chef server rebuild?

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I'm new to chef, but looking at setting up a chef server for serving cookbooks
to a few dozen nodes. 

I've been through the tutorials, but have started to wonder about the chef
server.

For example, If I have 20+ nodes connected to the chef server, all those nodes
were set up via knife bootstrap, specifying a “node” name, "websrv01" or
"dbsrv03"... Chef server crashes, and needs to be rebuilt. I reinstall the OS
on the server, put on chef server, put on the run lists and put all the
cookbooks back. 

How does the chef server identify some server running chef-client as node
“websrv04"? How can I save away and restore that node information?