VISA Patch System¶

NOTE This documentation is work in progress

Description¶

The VISA Patch System was put into place to allow us to apply new patches to VISA instance after a simple reboot and to address the need of urgent and frequent corrections during a reactor cycle, without having to fully re-build an image every time.

As part of the cloud-init package, when the instances are created, VISA uses a mechanism called User-Data which allows us to execute a script on first boot. This script is associated with a VISA Image and is configured in the boot command of the Images admin interface.

This script downloads an up-to-date script (or scripts) that should be executed when the instance starts, before a user has connected to it.

On instance creation, VISA also pushes the instance owner name (otherwise unknown at boot) into cloud-init metadata, stored in /run/cloud-init/instance-data.json on the instance.

This allows us, for example, to create a local home an environment for the user.

Example project¶

An example project is being developed and will be integrated soon