Stemcells

In order to manage BOSH stemcells in anynines-deployment, we've made stemcells configurable via the IaaS config. We configure a list of stemcells in iaas.stemcells (see config/iaas-config.yml.example for an example). This has the benefit of having all stemcells configured in one location and having it referenced anywhere it's needed. It also allows to use one type of stemcell in the services and another in the Service Instances. You can also use ops files to configure a certain type of stemcells for a particular component. This gives you a lot of control while preserving DRY principles by using sensible defaults.

Currently, Ubuntu Jammy is the default stemcell for all services and Service Instances. This can be changed to any OS supported by anynines-deployment.

note

In general, Ubuntu Xenial and Ubuntu Bionic are no longer supported.

Currently supported stemcells

note

Currently, only the Ubuntu Jammy stemcell is supported on compatible CPIs.

We've tested the following versions on our test system:

Linux stemcells	Versions	Comment
Ubuntu Jammy	1.829
Ubuntu Bionic	1.204	Unsupported
Ubuntu Xenial	621.125	Unsupported

Changing the default stemcell

caution

Before changing the default Stemcell for existing a9s PostgreSQL 13 instances, carefully read this documentation: Updating a9s PostgreSQL 13 to Jammy Stemcell.

We use YAML anchors to create a reference to a particular stemcell and use that reference throughout the IaaS config file. Please find the string &a9s-stemcell-default in the IaaS config file (example: config/iaas-config.yml.example) and "move" the string (a so called YAML anchor) to another stemcell. You can also introduce a different stemcell below the stemcell that uses this YAML anchor and assign it the YAML anchor &a9s-stemcell-default. After that, the default stemcell will be the one you configured.

An example for your IaaS config:

iaas:
  stemcells:
    ubuntu-jammy: &a9s-stemcell-default
      os: ubuntu-jammy
      alias: ubuntu-jammy
      version: "1.829"
      url: https://storage.googleapis.com/bosh-aws-light-stemcells/1.829/light-bosh-stemcell-1.829.tgz
      sha1: f771a15528f2e701bbd465ce486609f44e3a83bf

You can then reference such a stemcell like e.g.:

logme2_service:
  stemcells:
    service: *a9s-stemcell-default

If you want to use a different stemcell or even stemcell version in your service instances only, you can do so by using an Ops file. Please find an example in ops/replace-stemcell-template-uploader.yml You might have to create your own copy of that Ops file with the correct values for your setup.

Example IaaS config

The following YAML text is an example IaaS configuration. It introduces a stemcell (Ubuntu Jammy) and allows referring to it by using a YAML anchor (&a9s-stemcell-default.

iaas:
  stemcells:
    ubuntu-jammy: &a9s-stemcell-default
      os: ubuntu-jammy
      alias: ubuntu-jammy
      version: 1.829
      sha1: f771a15528f2e701bbd465ce486609f44e3a83bf

In order to refer to them, you can use a YAML alias:

iaas:
  data_service:
    stemcell: *a9s-stemcell-default

Once you introduced the anchors and an alias, you can refer to these stemcells in different ways:

stemcells:
- os: ((iaas.data_service.stemcells.service.os))
  alias: ((iaas.data_service.stemcells.service.alias))
  version: ((iaas.data_service.stemcells.service.version))

- name: jobname
  vm_type: small
  instances: 1
  azs: [z1, z2, z3]
  stemcell: ((iaas.data_service.stemcells.service.alias))
  jobs:
  - { name: jobname, release: jobrelease }
  properties:
    ...