User data is a way to automatically provision your instance with additional software or settings. You can provide a set of commands (a script) or enter cloud-config information as YAML. It is important to understand that the User Data provided will be used only when the machine is created.

Cloud Init Datasources

Historically, Exoscale templates used the Cloudstack cloud-init datasource. Since Cloud Init version 19.3, Exoscale has its own datasource.

Although the new Exoscale datasource is backwards-compatible with the Cloudstack datasource, new features such as managed private networks require using the Exoscale datasource. We recommend using the Exoscale datasource for all installations.

Adding user data

When you create a new instance, the wizard lets you enter user data at the bottom of the form.

You can find everything that can be done with user data and Cloud-Init in the documentation

Example: Script

In this example, we install screen and htop on an Ubuntu instance using Apt after having upgraded all packages on an Debian/Ubuntu system.

Add the following to the User Data field to install the screen package:

#cloud-config
runcmd:
    - apt-get --yes upgrade
    - apt-get --yes install screen htop

Note: Cloud-Init has pre-built directives for many items. Therefore, the previous scripts launched as command lines can be achieved with:

#cloud-config
package_upgrade: true
packages:
  - screen
  - htop

Example: Cloud-Config YAML

We will set our locale to en_US.UTF-8 using cloud-config YAML. Add the following YAML in the user data:

#cloud-config
locale: "en_US.UTF-8"

Example: Installing Wordpress

See our Wordpress tutorial.

Querying the User Data and Meta Data from the Instance

User Data and Meta Data can be retrieved from an instance to integrate in scripts for example or configuration management tools. This information is published on the Link Local Address 169.254.169.254 which is private between the hypervisor and the running instance.

  • User Data (the cloud-config contents)
curl http://metadata.exoscale.com/latest/user-data
  • Meta Data, such as instance size or IP address
curl http://metadata.exoscale.com/latest/meta-data
curl http://metadata.exoscale.com/latest/meta-data/public-ipv4

The list of available metadata is:

metadata name description
availability-zone The zone - datacenter in which the instance is running
cloud-identifier Returns “Exoscale Compute Platform” if running on Exoscale
instance-id The unique identifier or UUID for the instance
local-hostname The name of the instance as set during the add instance phase
local-ipv4 The primary network IP address of the instance
public-hostname Same as local-hostname
public-ipv4 The public IP address of the instance
public-keys The associated SSH public key associated to the instance
service-offering The size of the instance
vm-id Same as instance-id

Adding Password Management to Your Templates

Exoscale provides an optional password reset feature that allows users to set a temporary admin or root password as well as reset the existing admin or root password from the Exoscale Portal.

This password is provided to an instance via the Link Local Address 169.254.169.254 on port 8080:

curl  --header "DomU_Request: send_my_password" http://169.254.169.254:8080

After the password is retrieved and changed on the running instance, issue a command to indicate that the password was saved and that it can be deleted:

curl  --header "DomU_Request: saved_password" http://169.254.169.254:8080

Notes:

  • Linux-based distributions with a standard Cloud-Init implementation will follow the process outlined above automatically if the system allows for password-based logins.
  • Passwords are only provided one time back to the user who starts or resets an instance and are not persisted at the orchestration layer.