StarCluster Configuration File

The StarCluster configuration file uses ini formatting. It is made up of various sections which are described here in detail. This document explains how to configure the three required sections [aws info], [keypair], and [cluster] as well as optional [global], [volume], and [plugin] sections.

Creating the configuration file

The default starcluster config lives in ~/.starcluster/config. You can either create this file manually or have starcluster create it for you with an example configuration template (recommended).

To have StarCluster generate an example configuration file (~/.starcluster/config), simply run “starcluster help” at the command-line. Provided that the configuration file does not exist, you will see the following:

user@localhost$ starcluster help
StarCluster - (
Software Tools for Academics and Researchers (STAR)
Please submit bug reports to - ERROR - Config file /home/user/.starcluster/config does not exist

[1] Show the StarCluster config template
[2] Write config template to /home/user/.starcluster/config
[q] Quit

Plase enter your selection:

Selecting 1 will print the example configuration file template to standard output.

Selecting 2 will write the configuration file template to ~/.starcluster/config

The configuration template provided by StarCluster should be ready to go out-of-the-box after filling in your Amazon Web Services credentials and setting up a keypair. This example config provides a simple cluster template called ‘smallcluster’. This ‘smallcluster’ template is also set as the default cluster template. The following sections explain each section of the config and their options.

Amazon Web Services Credentials

The first required section in the configuration file is [aws info]. This section specifies all of your AWS credentials. The following settings are required

[aws info]
# replace these with your AWS keys (required)
aws_access_key_id = #your_aws_access_key_id
aws_secret_access_key = #your_secret_access_key
# these settings are optional and only used for creating new AMIs
aws_user_id= #your userid
ec2_cert = /path/to/your/ec2_cert.pem
ec2_private_key = /path/to/your/ec2_pk.pem

Amazon EC2 Regions

StarCluster uses the us-east-1 EC2 region by default. If you wish to use a different EC2 region you will need to specify the following additional settings in your [aws info] section:

[aws info]
aws_region_name = eu-west-1
aws_region_host =

Here aws_region_name is the name of the region you wish to use and aws_region_host is the region-specific EC2 endpoint host. Below is a table of EC2 region-specific endpoints:

aws_region_name aws_region_host

The above table is only for convenience. You will likely want to check the official list from Amazon instead.

Amazon S3 Region-Specific Endpoints

StarCluster uses as the S3 endpoint by default. If you’d like to switch S3 endpoints you can do so by specifying an additional aws_s3_host setting in your [aws info] section:

[aws info]
aws_region_name = us-west-1
aws_region_name =
aws_s3_host =

Below is a table of S3 region-specific endpoints:

Region aws_s3_host


Switching S3 endpoints is usually not necessary. From amazon: Switching to a region-specific S3 endpoint is completely optional. The main advantage of doing so is to reduce the temporary latency you might experience immediately after creating a bucket in a specific region. This temporary latency typically lasts less than one hour.

Amazon EC2 Keypairs

In addition to supplying your [aws info] you must also define at least one [keypair] section that represents one of your keypairs on Amazon EC2. Amazon EC2 keypairs are used by StarCluster to connect and configure your instances.

You should define a new [keypair] section for each Amazon EC2 keypair you wish to use with StarCluster. As an example, suppose we have two keypairs on Amazon EC2 that we wish to use with StarCluster named “mykeypair1” and “mykeypair2” on Amazon.


If you do not know the name of your keypair(s), use StarCluster’s listkeypairs command or the ec2-describe-keypairs command in the EC2 command line tools. The [keypair] section name must match the name of the keypair on Amazon EC2.

To configure StarCluster for these keypairs we define a [keypair] section for each of them in the configuration file:

[keypair mykeypair1]
# this is the path to your openssh private key for mykeypair4

[keypair mykeypair3]
# this is the path to your openssh private key for mykeypair2

These keypair sections can now be referenced in a cluster templateskeyname setting as we’ll show below in an example cluster template.


In order for StarCluster to interact with any instances you have on EC2, the keypair used to launch those instances must be defined in the config. You can check what keypairs were used to launch an instance using StarCluster’s listinstances command or the ec2-describe-instances command from the ec2 command-line tools.

Defining Cluster Templates

In order to launch StarCluster(s) on Amazon EC2, you must first provide a cluster template that contains all of the configuration for the cluster. A cluster template is simply a [cluster] section in the config. Once a cluster template has been defined, you can launch multiple StarClusters from it. Below is an example cluster template called ‘smallcluster’ which defines a 2-node cluster using m1.small EC2 instances and the mykeypair1 keypair we defined above.

# Sections starting with "cluster" define your cluster templates
# The section name is the name you give to your cluster template e.g.:
[cluster smallcluster]
# change this to the name of one of the keypair sections defined above
# (see the EC2 getting started guide tutorial on using ec2-add-keypair to learn
# how to create new keypairs)
keyname = mykeypair1

# number of ec2 instances to launch
cluster_size = 2

# create the following user on the cluster
cluster_user = sgeadmin
# optionally specify shell (defaults to bash)
# options: bash, zsh, csh, ksh, tcsh
cluster_shell = bash

# AMI for master node. Defaults to NODE_IMAGE_ID if not specified
# The base i386 StarCluster AMI is ami-0330d16a
# The base x86_64 StarCluster AMI is ami-0f30d166
master_image_id = ami-0330d16a

# instance type for master node.
# defaults to NODE_INSTANCE_TYPE if not specified
master_instance_type = m1.small

# AMI for worker nodes.
# Also used for the master node if MASTER_IMAGE_ID is not specified
# The base i386 StarCluster AMI is ami-0330d16a
# The base x86_64 StarCluster AMI is ami-0f30d166
node_image_id = ami-0330d16a

# instance type for worker nodes. Also used for the master node if
# MASTER_INSTANCE_TYPE is not specified
node_instance_type = m1.small

# availability zone
availability_zone = us-east-1c

Defining Multiple Cluster Templates

You are not limited to defining just one cluster template. StarCluster allows you to define multiple independent cluster templates by simply creating a new [cluster] section with all of the same settings (different values of course).

However, you may find that defining new cluster templates is some what repetitive with respect to redefining the same settings over and over. To remedy this situation, StarCluster allows cluster templates to extend other cluster templates:

[cluster mediumcluster]
# Declares that this cluster uses smallcluster's settings as defaults
extends = smallcluster
# this rest of this section is identical to smallcluster except for the following settings:
keyname = mykeypair2
node_instance_type = c1.xlarge
cluster_size = 8
volumes = biodata2

In the example above, mediumcluster will use all of smallcluster‘s settings as defaults. All other settings in the mediumcluster template override these defaults. For the mediumcluster template above, we can see that mediumcluster is the same as smallcluster except for its keyname, node_instance_type, cluster_size, and volumes settings.

Setting the Default Cluster Template

StarCluster allows you to specify a default cluster template to be used when using the “start” command. This is useful for users that mostly use a single cluster template. To define a default cluster template, define a [global] section and configure the default_template setting:

default_template = smallcluster

The above example sets the ‘smallcluster’ cluster template as the default.


If you do not specify a default cluster template in the config you will have to specify one at the command line using the –cluster-template option.

Amazon EBS Volumes


Using EBS volumes with StarCluster is completely optional. If you do not wish to use EBS volumes with StarCluster, simply do not define any [volume] sections and remove or comment-out the volumes setting from your cluster template(s).


If you do not use an EBS volume with StarCluster, any data that you wish to keep around after shutdown must be manually copied somewhere outside of the cluster (e.g. download the data locally or move it to S3 manually). This is because local instance storage on EC2 is ephemeral and does not persist after an instance has been shutdown. The advantage of using EBS volumes with StarCluster is that when you shutdown a particular cluster, any data saved on an EBS volume attached to that cluster will be available the next time the volume is attached to another cluster or EC2 instance.

StarCluster has the ability to use Amazon EBS volumes to provide persistent data storage on a given cluster. If you wish to use EBS volumes with StarCluster you will need to define a [volume] section in the configuration file for each volume you wish to use with StarCluster and then add this [volume] section name to a cluster template‘s volumes setting.

To configure an EBS volume for use with Starcluster, define a new [volume] section for each EBS volume. For example, suppose we have two volumes we’d like to use: vol-c9999999 and vol-c8888888. Below is an example configuration for these volumes:

[volume myvoldata1]
# this is the Amazon EBS volume id
# the path to mount this EBS volume on
# (this path will also be nfs shared to all nodes in the cluster)

[volume myvoldata2]

[volume myvoldata2-alternate]
# same volume as myvoldata2 but uses 2nd partition instead of 1st

StarCluster by default attempts to mount either the entire drive or the first partition in the volume onto the master node. It is possible to use a different partition by configuring a partition setting in your [volume] section as in the myvoldata2-alternate example above.

After defining one or more [volume] sections, you then need to add them to a cluster template in order to use them. To do this, specify the [volume] section name(s) in the volumes setting in one or more of your cluster templates. For example, to use both myvoldata1 and myvoldata2 from the above example in a cluster template called smallcluster:

[cluster smallcluster]
volumes = myvoldata1, myvoldata2

Now any time a cluster is started using the smallcluster template, myvoldata1 will be mounted to /home on the master, myvoldata2 will be mounted to /scratch on the master, and both /home and /scratch will be NFS shared to the rest of the cluster nodes.

Amazon Security Group Permissions

When starting a cluster each node is added to a common security group. This security group is created by StarCluster and has a name of the form “@sc-<cluster_tag>” where <cluster_tag> is the name you provided to the “start” command.

By default, StarCluster adds a permission to this security group that allows access to port 22 (ssh) from all IP addresses. This is needed so that StarCluster can connect to the instances and configure them properly. If you want to specify additional security group permissions to be set after starting your cluster you can do so in the config by creating one or more [permission] sections. These sections can then be specified in one or more cluster templates. Here’s an example that opens port 80 (web server) to the world for the smallcluster template:

[permission www]
# open port 80 to the world
from_port = 80
to_port = 80

[permission ftp]
# open port 21 only to a single ip
from_port = 21
to_port = 21
cidr_ip =

[permission myrange]
# open all ports in the range 8000-9000 to the world
from_port = 8000
to_port = 9000

[cluster smallcluster]
permissions = www, ftp, myrange

A permission section specifies a port range to open to a given network range (cidr_ip). By default, the network range is set to which represents any ip address (ie the “world”). In the above example, we created a permission section called www that opens port 80 to the “world” by setting the from_port and to_port both to be 80. You can restrict the ip addresses that the rule applies to by specifying the proper cidr_ip setting. In the above example, the ftp permission specifies that only ip address can access port 21 on the cluster nodes.

Defining Plugins

StarCluster also has support for user contributed plugins (see StarCluster Plugin System). To configure a cluster template to use a particular plugin, we must first create a plugin section for each plugin we wish to use. For example, suppose we have two plugins myplug1 and myplug2:

[plugin myplug1]
setup_class = myplug1.SetupClass
myplug1_arg_one = 2

[plugin myplug2]
setup_class = myplug2.SetupClass
myplug2_arg_one = 3

In this example, myplug{1,2}_arg_one are arguments to the plugin’s setup_class. The ‘myplug{1,2}_arg_one’ variable names were made up for this example. The names of these arguments depend on the plugin being used. Some plugins may not even have arguments.

After you’ve defined some [plugin] sections, you can reference them in a cluster template like so:

[cluster mediumcluster]
# Declares that this cluster uses smallcluster's settings as defaults
extends = smallcluster
# this rest of this section is identical to smallcluster except for the following settings:
keyname = mykeypair2
node_instance_type = c1.xlarge
cluster_size = 8
volumes = biodata2
plugins = myplug1, myplug2

Notice the added plugins setting for the ‘mediumcluster’ template. This setting instructs StarCluster to first run the ‘myplug1’ plugin and then the ‘myplug2’ plugin afterwards. Reversing myplug1/myplug2 in the plugins setting in the above example would reverse the order of execution.

See also

See also the documentation for the StarCluster Plugin System