5527f09778
These reintroduces the braindead '744' syntax for file permissions. Even
though this number isn't octal, it is assumed by convention to be. In
order to pull this off, coerceNodes() was introduced to try to
counteract the type inferrencing that occurs during the yaml
unmarshalling. The config is unmarshalled twice: once into an empty
interface and once into the CloudConfig structure. The two resulting
node structures are combined together. The nodes from the CloudConfig
process replace those from the interface{} when the types of the two
nodes are compatible. For example, with the input `0744`, yaml
interprets that as the integer 484 giving us the nodes '0744'(string)
and 484(int). Because the types string and int are compatible, we opt to
take the string node instead of the integer.
coreos-cloudinit 
coreos-cloudinit enables a user to customize CoreOS machines by providing either a cloud-config document or an executable script through user-data.
Configuration with cloud-config
A subset of the official cloud-config spec is implemented by coreos-cloudinit. Additionally, several CoreOS-specific options have been implemented to support interacting with unit files, bootstrapping etcd clusters, and more. All supported cloud-config parameters are documented here.
The following is an example cloud-config document:
#cloud-config
coreos:
units:
- name: etcd.service
command: start
users:
- name: core
passwd: $1$allJZawX$00S5T756I5PGdQga5qhqv1
write_files:
- path: /etc/resolv.conf
content: |
nameserver 192.0.2.2
nameserver 192.0.2.3
Executing a Script
coreos-cloudinit supports executing user-data as a script instead of parsing it as a cloud-config document. Make sure the first line of your user-data is a shebang and coreos-cloudinit will attempt to execute it:
#!/bin/bash
echo 'Hello, world!'
user-data Field Substitution
coreos-cloudinit will replace the following set of tokens in your user-data with system-generated values.
| Token | Description |
|---|---|
| $public_ipv4 | Public IPv4 address of machine |
| $private_ipv4 | Private IPv4 address of machine |
These values are determined by CoreOS based on the given provider on which your machine is running. Read more about provider-specific functionality in the CoreOS OEM documentation.
For example, submitting the following user-data...
#cloud-config
coreos:
etcd:
addr: $public_ipv4:4001
peer-addr: $private_ipv4:7001
...will result in this cloud-config document being executed:
#cloud-config
coreos:
etcd:
addr: 203.0.113.29:4001
peer-addr: 192.0.2.13:7001