Upgrading

cOS and every derivative can upgrade, rollback or just switch to different versions in runtime by using the toolkit installed inside the image.

To upgrade an installed system, just run elemental upgrade and reboot.

This will perform an upgrade based on the default derivative configuration for the image. See general configuration on how to configure defaults when building a derivative.

“Upgrades” are not carried over the usual way of treating each single package individually: cOS considers the container image as a new system where to boot into. It will pull a new container image during this phase, which will be booted on the next reboot.

Upgrade to a specific container image

To specify a specific container image to upgrade to instead of the regular upgrade channels, run elemental upgrade --docker-image image.

Note by default elemental upgrade --docker-image checks images against the notary registry server for valid signatures for the images tag. To disable image verification, run elemental upgrade --no-verify --docker-image.

Integration with System Upgrade Controller

If running a kubernetes cluster on the cOS system, you can leverage the system-upgrade-controller to trigger upgrades to specific image versions, for example:

---
apiVersion: upgrade.cattle.io/v1
kind: Plan
metadata:
  name: elemental-upgrade
  namespace: system-upgrade
  labels:
    k3s-upgrade: server
spec:
  concurrency: 1
  version:  fleet-sample # Image tag
  nodeSelector:
    matchExpressions:
      - {key: k3s.io/hostname, operator: Exists}
  serviceAccountName: system-upgrade
  cordon: true
#  drain:
#    force: true
  upgrade:
    image: quay.io/costoolkit/test-images # Image upgrade reference
    command:
    - "/usr/sbin/suc-upgrade"

See also trigger upgrades with fleet

From ISO

The ISO can be also used as a recovery medium: type elemental upgrade from a LiveCD. It will then try to upgrade the image of the active partition installed in the system.

How it works

cOS during installation sets two .img images files in the COS_STATE partition:

• /cOS/active.img labeled COS_ACTIVE: Where cOS typically boots from
• /cOS/passive.img labeled COS_PASSIVE: Where cOS boots for fallback

Those are used by the upgrade mechanism to prepare and install a pristine cOS each time an upgrade is attempted.