Support policy

Container-Optimized OS is tested and qualified for running various container workloads on Google Cloud. It is actively patched with security updates (CVEs) and bug-fixes to address issues that impact Google Cloud users. Users get access to these fixes via our image releases in the cos-cloud project.

Release support duration

A major version on Container-Optimized OS corresponds to a new Release Milestone as explained in Release channels. After becoming stable, most Release Milestones (or major versions) are actively supported for approximately 6 weeks. During these 6 weeks, the release milestone will get critical bug fixes and security updates.

Roughly twice each year, the Container-Optimized OS team will release a long term support (LTS) milestone. After becoming stable, LTS milestones are actively supported for approximately 15 months. LTS milestones follow the usual development cycle that is described in Release channels, meaning that they still go through the dev, beta, and stable release channels. However, once a LTS milestone becomes stable, it will continue to receive security updates and critical bug fixes for approximately 15 months, as opposed to 6 weeks for a typical milestone.

At the end of a milestone's support window, the release milestone is deprecated. Specifically, we set the DEPRECATED flag on images in that milestone and those images stop showing in the active list of images in the cos-cloud project.

Images in a deprecated milestone are still usable, but issues with those images will only be fixed in newer milestones. Users may see a warning if they are using the gcloud command-line tool while accessing deprecated images.

Users must upgrade to one of the newer active milestones to continue to have easy access to bug fixes and security patches.

Release quality

Every major release milestone goes through dev, beta and stable phases (also described in detail in Release channels). These correspond to cos-dev, cos-beta and cos-stable image families in the cos-cloud project.

You can identify the stage a release is at by looking at the image name (example: cos-stable-54-8743-71-0) or by looking at the image family it belongs to (example: cos-stable) as listed by gcloud compute images list --project=cos-cloud --no-standard-images command.

Once a LTS milestone becomes stable, a corresponding image family is added to the cos-cloud project (example: cos-69-lts). This family can be used to identify the latest image on a specific LTS milestone.

Users can always expect to see at least 1 image in the cos-dev, cos-beta, and cos-stable families.

Release milestone progression

Progression for normal milestones is visualized in the following diagram.

Progression of a release milestone

LTS milestones follow a similar schedule. LTS milestones are only different in that they are stable for a much longer period of time.

Please refer to Release channels for a detailed explanation of each of the dev, beta, and stable stages. Each stage receives varying degrees of attention with respect to our support policy. This is explained below.

Image Family Duration (Soak Period) Release Frequency Properties
cos-dev ~6 weeks Weekly
  • A new major version is always introduced in `cos-dev` family first.
  • The new major version stays in `cos-dev` for approximately 6 weeks (soak period)
  • New images are released once a week
  • Gets bug fixes, package upgrades and new features
  • May introduce breaking changes compared to previous major version.
  • After the soak period, the major version is promoted to `cos-beta` family
cos-beta ~6 weeks Weekly
  • Feature set is frozen and no major version changes of packages. So breaking changes are not expected.
  • New images are released once a week
  • Get security fixes and other major bug fixes affecting already built-in features and majority of users
  • Approximately 6 weeks of soak period, after which the major version is promoted to `cos-stable` family. If the major version is LTS, it will also be promoted to a LTS family.
cos-stable ~6 weeks on-demand
  • New images are released only for critical bug fixes and security fixes
  • A major version is available on `cos-stable` for approximately 6 weeks
major version LTS family ~15 months on-demand
  • There is a LTS family for each stable LTS major version (example: cos-69-lts)
  • New images are released only for critical bug fixes and security fixes
  • A major version is available on a LTS family for approximately 15 months
  • After approximately 15 months, a major version's LTS family becomes unavailable

Contact us