Custom Scripts


Custom Scripts are scripts that use the cloud-config format, designed to be run by the cloud-init process. These scripts are generally used for the initial configuration of a server and run on the first boot.

Put simply, deploying a server with a custom script allows you to run arbitrary commands and change several aspects of the server during provisioning.

Here are a few examples of what you can do with a very simple custom script:

  • Define machine hostname
  • Add SSH keys
  • Change user passwords

File format

UNIX-like systems

If you're using a UNIX-like O.S. such as Linux, your scripts must be written using the YAML file format, which uses whitespace and new-lines to delimit lists, associative arrays, and values.

These files are generally fairly intuitive and easy to understand, but there are a few things you need to keep in mind when using them. Here is a good getting started guide from the guys at Ansible that can help.

Always validate your YAML code. Google YAML validator if you don't have a linter on your IDE, but remember never to add sensitive data.

Windows systems

For Windows images, you'll have to use the cloud-baseinit convention. This is just a fancy way of saying that your custom scripts will have to be written as if you were using the Powershell. Here's a straightforward example:

mkdir c:/test
New-Item c:/test/test.txt
Set-Content c:/test/test.txt 'Hello World'

Adding a custom script

  1. When creating a new server, click on New custom script. (Or go to Servers > Custom Scripts)
    Image_2019-11-12_at_5.00.25_PM.png
  2. The name of your script needs to be preceded by a number and a dash. We use this to define the order of the scripts that you select. For instance, a script named 01-Script will run before 02-Script because 01 takes priority over 02.
  3. Click on add and proceed with deploying your server.

Examples

You can find great examples on cloud-init's docs here.


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