You can override the variables defined in [config-default.sh](http://releases.k8s.io/{{page.githubbranch}}/cluster/aws/config-default.sh) to change this behavior as follows:
If you don't specify master and minion sizes, the scripts will attempt to guess
the correct size of the master and worker nodes based on `${NUM_NODES}`. In
version 1.2 these default are:
* For the master, for clusters of less than 150 nodes it will use an
`m3.medium`, for clusters of greater than 150 nodes it will use an
`m3.large`.
* For worker nodes, for clusters less than 50 nodes it will use a `t2.micro`,
for clusters between 50 and 150 nodes it will use a `t2.small` and for
clusters with greater than 150 nodes it will use a `t2.medium`.
WARNING: beware that `t2` instances receive a limited number of CPU credits per hour and might not be suitable for clusters where the CPU is used
consistently. As a rough estimation, consider 15 pods/node the absolute limit a `t2.large` instance can handle before it starts exhausting its CPU credits
steadily, although this number depends heavily on the usage.
In prior versions of Kubernetes, we defaulted the master node to a t2-class
instance, but found that this sometimes gave hard-to-diagnose problems when the
master ran out of memory or CPU credits. If you are running a test cluster
and want to save money, you can specify `export MASTER_SIZE=t2.micro` but if
your master pauses do check the CPU credits in the AWS console.
For production usage, we recommend at least `export MASTER_SIZE=m3.medium` and
`export NODE_SIZE=m3.medium`. And once you get above a handful of nodes, be
aware that one m3.large instance has more storage than two m3.medium instances,
for the same price.
We generally recommend the m3 instances over the m4 instances, because the m3
instances include local instance storage. Historically local instance storage
has been more reliable than AWS EBS, and performance should be more consistent.
The ephemeral nature of this storage is a match for ephemeral container
workloads also!
If you use an m4 instance, or another instance type which does not have local
instance storage, you may want to increase the `NODE_ROOT_DISK_SIZE` value,
although the default value of 32 is probably sufficient for the smaller
instance types in the m4 family.
The script will also try to create or reuse a keypair called "kubernetes", and IAM profiles called "kubernetes-master" and "kubernetes-minion".
CoreOS maintains [a CLI tool](https://coreos.com/kubernetes/docs/latest/kubernetes-on-aws.html), `kube-aws` that will create and manage a Kubernetes cluster based on [CoreOS](http://www.coreos.com), using AWS tools: EC2, CloudFormation and Autoscaling.
The "Guestbook" application is another popular example to get started with Kubernetes: [guestbook example](https://github.com/kubernetes/kubernetes/tree/{{page.githubbranch}}/examples/guestbook/)
For more complete applications, please look in the [examples directory](https://github.com/kubernetes/kubernetes/tree/{{page.githubbranch}}/examples/)
## Tearing down the cluster
Make sure the environment variables you used to provision your cluster are still exported, then call the following script inside the
