Attaching a start up script to an instance template

> Have the same issue with Jenkins 2.249.3 and compute engine plugin 4.3.3 despite installing java in "Startup script" section. Image used: "ubuntu-2004-focal-v20201028"
>
> The issue appears to be related to:
> #165
>
> #166
> #186

Have you got OSLogin enabled globally? If so then you you will need to create an instance template outside of jenkins and disable OSLogin within the metadata. In Jenkins then you just reference the instance template that you've already created.

That was how I resolved the issue in my case. OSLogin is enabled globally but the GCP Plugin in Jenkins doesn't seem to work when it is enabled so you need to disable it for any Jenkins nodes

_Originally posted by @emmaLP in https://github.com/jenkinsci/google-compute-engine-plugin/issues/194#issuecomment-728144929_

Sorry, I know this is a long time after this issue but please would you know if it was possible to attach a start up script to an instance template (not a vm instance) and if possible how to do so? I have successfully set up an instance template in jenkins that was cloned from an existing vm instance that had Java 11 installed but when the on-demand agents are created in GCP, I get the Java not installed error. I am hoping that a start up script will install Java on the fly, on the agents created from the template...Thanks

Review the Google Compute Engine plugin's instance-template configuration and the related issues #165, #166, and #186 first. Reproduce the behavior with Jenkins 2.249.3, plugin 4.3.3, the Ubuntu 20.04 image, and OSLogin enabled; done means a configured startup script is applied to agents created from the template.

Written by the indexing model from the issue text.