cloudinit/Documentation/coreos-init.md
2014-03-04 16:36:05 -08:00

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# coreos-init
CoreOS allows a user to customize EC2 instances by providing either an executable script or a cloud-config document as instance user-data. See below to learn how to use these features.
## cloud-config
Only a subset of [cloud-config functionality][cloud-config] is implemented. A set of custom parameters were added to the cloud-config format that are specific to CoreOS.
[cloud-config]: http://cloudinit.readthedocs.org/en/latest/topics/format.html#cloud-config-data
### Supported cloud-config Parameters
#### ssh_authorized_keys
Provided public SSH keys will be authorized for the `core` user.
### Custom cloud-config Parameters
#### coreos.etcd.discovery_url
The value of `coreos.etcd.discovery_url` will be used to discover the instance's etcd peers using the [etcd discovery protocol][disco-proto]. Usage of the [public discovery service][disco-service] is encouraged.
[disco-proto]: https://github.com/coreos/etcd/blob/master/Documentation/discovery-protocol.md
[disco-service]: http://discovery.etcd.io
## user-data Script
Simply set your user-data to a script where the first line is a shebang:
```
#!/bin/bash
echo 'Hello, world!'
```
## Examples
### Inject an SSH key and bootstrap an etcd cluster using cloud-config
```
#cloud-config
coreos:
etcd:
discovery_url: https://discovery.etcd.io/827c73219eeb2fa5530027c37bf18877
ssh_authorized_keys:
- ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQC0g+ZTxC7weoIJLUafOgrm+h...
```