When you create your cluster, you can customize the starting number of nodes (minions) with the NUM_MINIONS environment variable. By default, it is set to 4.

Additionally, the Kubernetes team has started to build autoscaling capability into the cluster itself. Currently, this is only supported on GCE and GKE, but work is being done on other providers. This capability utilizes the KUBE_AUTOSCALER_MIN_NODES, KUBE_AUTOSCALER_MAX_NODES, and KUBE_ENABLE_CLUSTER_AUTOSCALER environment variables.

The following example shows how to set the environment variables for autoscaling before running kube-up.sh:

$ export NUM_MINIONS=5
$ export KUBE_AUTOSCALER_MIN_NODES=2
$ export KUBE_AUTOSCALER_MAX_NODES=5
$ export KUBE_ENABLE_CLUSTER_AUTOSCALER=true

Also, bear in mind that changing this after the cluster is started will have no effect. You would need to tear down the cluster and create it once again. Thus, this section will show you how to add nodes to an existing cluster without rebuilding it.

Once you start a cluster with these settings, your cluster will automatically scale up and down with the minimum and maximum limits based on compute resource usage in the cluster.