Erratic behaviour when using packer to build agents

[imonike]

Hello everyone

I am trying to follow this tutorial to do distributed jenkins build

https://cloud.google.com/architecture/using-jenkins-for-distributed-builds-on-compute-engine

and I am getting inconsistent behaviour from packer when trying to use to build a jenkins agent. I modified the jenkis-agent.json to install Java 11 likes  this:

{
  "builders": [
    {
      "type": "googlecompute",
      "project_id": "elite-impact-378112",
      "source_image_family": "ubuntu-2004-lts",
      "source_image_project_id": "ubuntu-os-cloud",
      "zone": "us-central1-a",
      "disk_size": "50",
      "image_name": "jenkins-agent-{{timestamp}}",
      "image_family": "jenkins-agent",
      "ssh_username": "ubuntu"
    }
  ],
  "provisioners": [
    {
      "type": "shell",
      "inline": ["sudo apt-get update && sudo apt-get install -y openjdk-11-jdk"]
    }
  ]
}

because that is what I have running on the jenkins master node on my laptop. Now the first time I ran the packer build command in the gcloud shell

./packer build jenkins-agent.json

I got the following error

[0;32m    googlecompute: The following packages have unmet dependencies:[0m
[0;32m    googlecompute:  openjdk-11-jdk : Depends: openjdk-11-jre (= 11.0.18+10-0ubuntu1~20.04.1) but it is not going to be installed[0m
[0;32m    googlecompute:                   Depends: openjdk-11-jdk-headless (= 11.0.18+10-0ubuntu1~20.04.1) but it is not going to be installed[0m
[0;32m    googlecompute:                   Recommends: libxt-dev but it is not installable[0m
[1;31m==> googlecompute: E: Unable to correct problems, you have held broken packages.

Now since I was running this in the gcloud shell, most of the output was running off the screen. I wanted to see this output so decided to run the command again but redirecting to a file like this:

./packer build jenkins-agent.json > packer_build_output.txt

The funny thing that now happened was that the jenkins agent was successfully built this time with no change on my end other than redirecting the output. I was also able to succesfully perform the "Hello World" test in the tutorial. I now decided that I wanted to pull the "Hello World" code from GitHub so I modified the jenkins-agent.json to also install git. This packer build was also successful and the subsequent jenkins build was also successful. I now decided that I wanted to use Maven to build the code so I modified the jenkins-agent.json again to also install maven. This packer build failed. Before trying to debug the error, I wanted to make sure that the previous build of just Java 11 and git would still work so I removed the install maven code and ran the packer build again. This also failed with the original error message I posted earlier. Please I would appreciate any clues as to the inconsistency of packer because it is really driving me up the wall. Thank you

[Willbin]

Hello @imonike,

Welcome to Google Cloud Community!

Based on the error you posted, you have held broken packages error when trying to install 

openjdk-11-jdk

This is because a conflict was avoided by holding them down. That is why it is not installing, upgrading, downgrading, or removing. You can try:
1. Installing aptitude by running

sudo apt-get install -y aptitude

2. then run this for your held packages

sudo aptitude install <packagename>

This will give you more information about the problem. It will also tell you exactly what's wrong and offers you automatically to perform the fix on your behalf.  

[gcloizaga]

I tried what you suggested but it seems like google cannot found "aptitude" either. So at the end it doesn't create the instance.