Adds ec2-scripts.md back (it was mistakenly removed earlier due to

git weirdness).

docs/ec2-scripts.md

+---
+layout: global
+title: Using the Spark EC2 Scripts
+---
+The `spark-ec2` script located in the Spark's `ec2` directory allows you
+to launch, manage and shut down Spark clusters on Amazon EC2. It builds
+on the [Mesos EC2 script](https://github.com/mesos/mesos/wiki/EC2-Scripts)
+in Apache Mesos.
+
+`spark-ec2` is designed to manage multiple named clusters. You can
+launch a new cluster (telling the script its size and giving it a name),
+shutdown an existing cluster, or log into a cluster. Each cluster is
+identified by placing its machines into EC2 security groups whose names
+are derived from the name of the cluster. For example, a cluster named
+`test` will contain a master node in a security group called
+`test-master`, and a number of slave nodes in a security group called
+`test-slaves`. The `spark-ec2` script will create these security groups
+for you based on the cluster name you request. You can also use them to
+identify machines belonging to each cluster in the EC2 Console or
+ElasticFox.
+
+This guide describes how to get set up to run clusters, how to launch
+clusters, how to run jobs on them, and how to shut them down.
+
+Before You Start
+================
+
+-   Create an Amazon EC2 key pair for yourself. This can be done by
+    logging into your Amazon Web Services account through the [AWS
+    console](http://aws.amazon.com/console/), clicking Key Pairs on the
+    left sidebar, and creating and downloading a key. Make sure that you
+    set the permissions for the private key file to `600` (i.e. only you
+    can read and write it) so that `ssh` will work.
+-   Whenever you want to use the `spark-ec2` script, set the environment
+    variables `AWS_ACCESS_KEY_ID` and `AWS_SECRET_ACCESS_KEY` to your
+    Amazon EC2 access key ID and secret access key. These can be
+    obtained from the [AWS homepage](http://aws.amazon.com/) by clicking
+    Account \> Security Credentials \> Access Credentials.
+
+Launching a Cluster
+===================
+
+-   Go into the `ec2` directory in the release of Spark you downloaded.
+-   Run
+    `./spark-ec2 -k <keypair> -i <key-file> -s <num-slaves> launch <cluster-name>`,
+    where `<keypair>` is the name of your EC2 key pair (that you gave it
+    when you created it), `<key-file>` is the private key file for your
+    key pair, `<num-slaves>` is the number of slave nodes to launch (try
+    1 at first), and `<cluster-name>` is the name to give to your
+    cluster.
+-   After everything launches, check that Mesos is up and sees all the
+    slaves by going to the Mesos Web UI link printed at the end of the
+    script (`http://<master-hostname>:8080`).
+
+You can also run `./spark-ec2 --help` to see more usage options. The
+following options are worth pointing out:
+
+-   `--instance-type=<INSTANCE_TYPE>` can be used to specify an EC2
+instance type to use. For now, the script only supports 64-bit instance
+types, and the default type is `m1.large` (which has 2 cores and 7.5 GB
+RAM). Refer to the Amazon pages about [EC2 instance
+types](http://aws.amazon.com/ec2/instance-types) and [EC2
+pricing](http://aws.amazon.com/ec2/#pricing) for information about other
+instance types. 
+-    `--zone=<EC2_ZONE>` can be used to specify an EC2 availability zone
+to launch instances in. Sometimes, you will get an error because there
+is not enough capacity in one zone, and you should try to launch in
+another. This happens mostly with the `m1.large` instance types;
+extra-large (both `m1.xlarge` and `c1.xlarge`) instances tend to be more
+available.
+-    `--ebs-vol-size=GB` will attach an EBS volume with a given amount
+     of space to each node so that you can have a persistent HDFS cluster
+     on your nodes across cluster restarts (see below).
+-    If one of your launches fails due to e.g. not having the right
+permissions on your private key file, you can run `launch` with the
+`--resume` option to restart the setup process on an existing cluster.
+
+Running Jobs
+============
+
+-   Go into the `ec2` directory in the release of Spark you downloaded.
+-   Run `./spark-ec2 -k <keypair> -i <key-file> login <cluster-name>` to
+    SSH into the cluster, where `<keypair>` and `<key-file>` are as
+    above. (This is just for convenience; you could also use
+    the EC2 console.)
+-   To deploy code or data within your cluster, you can log in and use the
+    provided script `~/mesos-ec2/copy-dir`, which,
+    given a directory path, RSYNCs it to the same location on all the slaves.
+-   If your job needs to access large datasets, the fastest way to do
+    that is to load them from Amazon S3 or an Amazon EBS device into an
+    instance of the Hadoop Distributed File System (HDFS) on your nodes.
+    The `spark-ec2` script already sets up a HDFS instance for you. It's
+    installed in `/root/ephemeral-hdfs`, and can be accessed using the
+    `bin/hadoop` script in that directory. Note that the data in this
+    HDFS goes away when you stop and restart a machine.
+-   There is also a *persistent HDFS* instance in
+    `/root/presistent-hdfs` that will keep data across cluster restarts.
+    Typically each node has relatively little space of persistent data
+    (about 3 GB), but you can use the `--ebs-vol-size` option to
+    `spark-ec2` to attach a persistent EBS volume to each node for
+    storing the persistent HDFS.
+-   Finally, if you get errors while running your jobs, look at the slave's logs
+    for that job using the Mesos web UI (`http://<master-hostname>:8080`).
+
+Terminating a Cluster
+=====================
+
+***Note that there is no way to recover data on EC2 nodes after shutting
+them down! Make sure you have copied everything important off the nodes
+before stopping them.***
+
+-   Go into the `ec2` directory in the release of Spark you downloaded.
+-   Run `./spark-ec2 destroy <cluster-name>`.
+
+Pausing and Restarting Clusters
+===============================
+
+The `spark-ec2` script also supports pausing a cluster. In this case,
+the VMs are stopped but not terminated, so they
+***lose all data on ephemeral disks*** but keep the data in their
+root partitions and their `persistent-hdfs`. Stopped machines will not
+cost you any EC2 cycles, but ***will*** continue to cost money for EBS
+storage.
+
+- To stop one of your clusters, go into the `ec2` directory and run
+`./spark-ec2 stop <cluster-name>`.
+- To restart it later, run
+`./spark-ec2 -i <key-file> start <cluster-name>`.
+- To ultimately destroy the cluster and stop consuming EBS space, run
+`./spark-ec2 destroy <cluster-name>` as described in the previous
+section.
+
+Limitations
+===========
+
+- `spark-ec2` currently only launches machines in the US-East region of EC2.
+  It should not be hard to make it launch VMs in other zones, but you will need
+  to create your own AMIs in them.
+- Support for "cluster compute" nodes is limited -- there's no way to specify a
+  locality group. However, you can launch slave nodes in your
+  `<clusterName>-slaves` group manually and then use `spark-ec2 launch
+  --resume` to start a cluster with them.
+- Support for spot instances is limited.
+
+If you have a patch or suggestion for one of these limitations, feel free to
+[contribute]({{HOME_PATH}}contributing-to-spark.html) it!