Init container

Ondat has requirements for the configuration of host systems. As such, Ondat starts an init container that sets the system configuration for Ondat. The container also manages configuration changes required when upgrading Ondat versions.

The container belongs to the DaemonSet that the Ondat Cluster Operator starts when a StorageOSCluster resource is created. The storageos-init container is executed as an initContainer as part of a Kubernetes Pod. Therefore, only successful execution of the storageos-init container processes will result in the main container starting.

Script Framework

The code responsible for fulfilling the requirements is based on a Script Framework.

The script framework executes a set of scripts, performing checks, verifications and other procedures needed for Ondat to be able to start. The scripts stdout and stderr are written to the stdout and stderr of the init app. The container logs contain all the logs of the individual scripts that run. The exit statuses of the scripts are used to determine initialization failure or success. Any non-zero exit status is logged as an event in the Kubernetes Pod events.

If any of the scripts fail, the storageos-init container will propagate the failure to Kubernetes, showing the status of the Pod as Init:Err.

To view the output of all storageos-init containers the following command can be used:

kubectl -n kube-system logs -l app=storageos,kind=daemonset -c storageos-init

For more details, check the Ondat init container project.

Scripts executed

The storageos-init container executes the following scripts.