Updating Stemcells

This topic explains how to update Concourse component VM stemcells separately from updating Concourse itself.

Preferred Stemcell

The preferred stemcell version for Concourse v6.7.x is Ubuntu Xenial 621.x.

You can check your stemcell versions by running the command bosh stemcells.

Download the latest Xenial 621.x stemcell for your IaaS as follows:
1. Browse to Stemcells for Operations Manager (Ubuntu Xenial) on the Broadcom Support portal.
2. Select and download the latest Xenial 621.x stemcell version for your IaaS.
Upload the stemcell to the BOSH director by running the the following command:
```
bosh upload-stemcell PATH-TO-FILE
```
Where PATH-TO-FILE is the local path to the stemcell you downloaded.
Edit your Concourse manifest cluster/concourse.yml to target the stemcell version that you downloaded. By default, the Concourse manifest targets the latest stemcell as follows:
```
    ...
    stemcells:
    - alias: xenial
      os: ubuntu-xenial
      version: latest
    ...
```
To target a specific stemcell version, modify the version: setting as follows:
```
    ...
    stemcells:
    - alias: xenial
      os: ubuntu-xenial
      version: TARGET-VERSION
    ...
```
Where TARGET-VERSION is the version number of the uploaded stemcell, without quotes. For example, 621.95
Trigger an update by running your Concourse deploy script.

After Concourse has re-deployed, all Concourse VMs should be running the new stemcell version.