Building a Stemcell
(See What is a Stemcell? for an introduction to stemcells.)
To build a stemcell tarball for a supported IaaS-OS combination follow instructions in the bosh-linux-stemcell-builder's README.
Stemcell tarballs are currently specific to an IaaS-OS/CPI because they may:
- include custom Agent configuration (e.g. OpenStack's Agent configuration)
- include custom OS packages/configuration (e.g. OpenStack's OS customizations)
- be packaged into a custom image format (qcow, vmdk, etc.)
In the future, BOSH team will investigate how to best consolidate stemcells into a single OS image. In the meantime, if you're developing a CPI for a new IaaS, you may consider reusing one of the officially generated stemcells, or making changes to the following projects:
This is an implementation detail. The tarball structure is subject to change without notice.
$ tar tvf light-bosh-stemcell-3033-aws-xen-hvm-ubuntu-trusty-go_agent.tgz -rw-rw-r-- 0 ubuntu ubuntu 0 Aug 4 09:45 image -rw-rw-r-- 0 ubuntu ubuntu 710 Aug 4 10:06 stemcell.MF -rw-r--r-- 0 ubuntu ubuntu 50594 Aug 4 09:23 packages.txt -rw-r--r-- 0 ubuntu ubuntu 12543 Aug 4 09:22 dev_tools_file_list.txt
image: OS image in a format (raw, qcow, ova, etc.) understood by the CPI/IaaS.
stemcell.MF: YAML file with stemcell metadata.
packages.txt: Text file that includes list of packages installed. (Used to be included as
dev_tools_file_list.txt: Text file that includes list of files removed by the agent if Agent's
remove_dev_toolsfeature is enabled.
This is an implementation detail. The content of
stemcell.MF is subject to change without notice.
- name [String, required]: A unique name used to identify stemcell series.
- operating_system [String, required]: Operating system in the stemcell. Example:
- version [String, required]: Version of the stemcell. Example:
- sha1 [String, required]: The SHA1 of the image file included in the stemcell tarball.
- bosh_protocol [String, optional]: Deprecated.
- cloud_properties [Hash, required]: Describes any IaaS-specific properties needed to import OS image. These properties will be passed in to the
- stemcell_formats [Array of Strings, optional]: The list of stemcell formats that a CPI must support. The director will attempt to upload the stemcell to all CPIs that support any specified formats.
Name, operating system and version values will be visible via
bosh stemcells command once a stemcell is imported into the Director.
$ tar -Oxzf light-bosh-stemcell-97.19-aws-xen-hvm-ubuntu-xenial-go_agent.tgz stemcell.MF
--- name: bosh-aws-xen-hvm-ubuntu-xenial-go_agent version: '97.19' bosh_protocol: '1' sha1: da39a3ee5e6b4b0d3255bfef95601890afd80709 operating_system: ubuntu-xenial stemcell_formats: - aws-light cloud_properties: ami: us-gov-west-1: ami-1431a975 ap-northeast-1: ami-0ddb32f9e2cb016f3 ap-northeast-2: ami-04f416b078c7eb965 ap-south-1: ami-0f04da873c8883a56 ap-southeast-1: ami-0628f639a2c1abd77 ap-southeast-2: ami-06f24628e83df3ca7 ca-central-1: ami-0b8196ea9d0c10b00 eu-central-1: ami-07ebdd782c27da598 eu-west-1: ami-0f7e184ff7b50cd36 eu-west-2: ami-01713a432b5494aa6 eu-west-3: ami-059850a6db5f0f1f0 sa-east-1: ami-0559933d31a7cbdf3 us-east-1: ami-0cdc0ee47ff314116 us-east-2: ami-05e20eb5a19355a32 us-west-1: ami-0eb351fd3b5bb07e0 us-west-2: ami-0147f5edb0c3600ab cn-northwest-1: ami-0855153be65a20e35 cn-north-1: ami-01db1b9ef2de116fb
Some IaaSes (or how they are configured) limit how OS images can be imported. Here are couple of examples:
- AWS only allows creation of AMIs from running VMs on AWS
- OpenStack can be configured to disallow Glance image upload
- an IaaS may take long time to import an image making it beneficial to reuse existing images
In such cases CPI must use already imported OS image and that's where light stemcells come in. Light stemcell tarballs include additional details about already imported OS images in the
cloud_properties section. For example light stemcells for AWS have
ami key in the
cloud_properties section (as shown above), that contains region-to-AMI-ID mappings. When AWS CPI's
create_stemcell call is made, it will return matching AMI ID without doing any IaaS API calls.
There are two test suites each stemcell is expected to pass before it's considered to be production-ready: