162 lines
5.8 KiB
Markdown
162 lines
5.8 KiB
Markdown
# Customize with Cloud-Config
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CoreOS allows you to configure networking, create users, launch systemd units on startup and more. We've designed our implementation to allow the same cloud-config file to work across all of our supported platforms.
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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. An example file containing all available options can be found at the bottom of this page.
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[cloud-config]: http://cloudinit.readthedocs.org/en/latest/topics/format.html#cloud-config-data
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## CoreOS Parameters
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### coreos.etcd.discovery_url
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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. **Note:** this is currently Amazon-only.
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```
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#cloud-config
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coreos:
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etcd:
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discovery_url: https://discovery.etcd.io/827c73219eeb2fa5530027c37bf18877
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```
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[disco-proto]: https://github.com/coreos/etcd/blob/master/Documentation/discovery-protocol.md
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[disco-service]: http://discovery.etcd.io
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### coreos.units
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Arbitrary systemd units may be provided in the `coreos.units` attribute.
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`coreos.units` is a list of objects with the following fields:
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- **name**: string representing unit's name
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- **runtime**: boolean indicating whether or not to persist the unit across reboots. This is analagous to the `--runtime` flag to `systemd enable`.
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- **content**: plaintext string representing entire unit file
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```
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#cloud-config
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coreos:
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units:
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- name: docker-redis.service
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content: |
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[Unit]
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Description=Redis container
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Author=Me
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After=docker.service
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[Service]
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Restart=always
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ExecStart=/usr/bin/docker start -a redis_server
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ExecStop=/usr/bin/docker stop -t 2 redis_server
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[Install]
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WantedBy=local.target
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```
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## Cloud-Config Parameters
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### ssh_authorized_keys
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Provided public SSH keys will be authorized for the `core` user.
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The keys will be named "coreos-cloudinit" by default.
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Override this with the `--ssh-key-name` flag when calling `coreos-cloudinit`.
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```
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#cloud-config
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ssh_authorized_keys:
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- ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQC0g+ZTxC7weoIJLUafOgrm+h...
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```
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### hostname
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The provided value will be used to set the system's hostname.
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This is the local part of a fully-qualified domain name (i.e. `foo` in `foo.example.com`).
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```
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#cloud-config
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hostname: coreos1
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```
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### users
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Add or modify users with the `users` directive by providing a list of user objects, each consisting of the following fields.
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Each field is optional and of type string unless otherwise noted.
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All but the `passwd` and `ssh-authorized-keys` fields will be ignored if the user already exists.
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- **name**: Required. Login name of user
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- **gecos**: GECOS comment of user
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- **passwd**: Hash of the password to use for this user
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- **homedir**: User's home directory. Defaults to /home/<name>
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- **no-create-home**: Boolean. Skip home directory creation.
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- **primary-group**: Default group for the user. Defaults to a new group created named after the user.
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- **groups**: Add user to these additional groups
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- **no-user-group**: Boolean. Skip default group creation.
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- **ssh-authorized-keys**: List of public SSH keys to authorize for this user
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- **coreos-ssh-import-github**: Authorize SSH keys from Github user
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- **system**: Create the user as a system user. No home directory will be created.
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- **no-log-init**: Boolean. Skip initialization of lastlog and faillog databases.
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The following fields are not yet implemented:
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- **inactive**: Deactivate the user upon creation
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- **lock-passwd**: Boolean. Disable password login for user
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- **sudo**: Entry to add to /etc/sudoers for user. By default, no sudo access is authorized.
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- **selinux-user**: Corresponding SELinux user
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- **ssh-import-id**: Import SSH keys by ID from Launchpad.
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```
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#cloud-config
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users:
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- name: elroy
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passwd: $6$5s2u6/jR$un0AvWnqilcgaNB3Mkxd5yYv6mTlWfOoCYHZmfi3LDKVltj.E8XNKEcwWm...
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groups:
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- staff
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- docker
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ssh-authorized-keys:
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- ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQC0g+ZTxC7weoIJLUafOgrm+h...
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```
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#### Generating a password hash
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If you choose to use a password instead of an SSH key, generating a safe hash is extremely important to the security of your system. Simplified hashes like md5crypt are trivial to crack on modern GPU hardware. Here are a few ways to generate secure hashes:
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```
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# On Debian/Ubuntu (via the package "whois")
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mkpasswd --method=SHA-512 --rounds=4096
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# OpenSSL (note: this will only make md5crypt. While better than plantext it should not be considered fully secure)
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openssl passwd -1
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# Python (change password and salt values)
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python -c "import crypt, getpass, pwd; print crypt.crypt('password', '\$6\$SALT\$')"
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# Perl (change password and salt values)
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perl -e 'print crypt("password","\$6\$SALT\$") . "\n"'
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```
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Using a higher number of rounds will help create more secure passwords, but given enough time, password hashes can be reversed. On most RPM based distributions there is a tool called mkpasswd available in the `expect` package, but this does not handle "rounds" nor advanced hashing algorithms.
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### write_files
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Inject an arbitrary set of files to the local filesystem.
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Provide a list of objects with the following attributes:
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- **path**: Absolute location on disk where contents should be written
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- **content**: Data to write at the provided `path`
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- **permissions**: String representing file permissions in octal notation (i.e. '0644')
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- **owner**: User and group that should own the file written to disk. This is equivalent to the `<user>:<group>` argument to `chown <user>:<group> <path>`.
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## user-data Script
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Simply set your user-data to a script where the first line is a shebang:
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```
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#!/bin/bash
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echo 'Hello, world!'
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```
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