OpenShift provides an Operators section in its web console UI for the installation and management of operators on the cluster.
The OperatorHub is an interface for searching and installing operators. It has the following categories of operators:
- Red Hat Operators: Operators developed and supported by Red Hat. Example: Red Hat Quay Operator
- Certified Operators: Operators listed by Red Hat’s Independent Software Vendors (ISVs). Example: CockroachDB Operator
- Red Hat Marketplace Operators: Applications purchased from Red Hat Marketplace available as Operators. Example: Dynatrace Operator
- Community Operators: Default catalog of Operators maintained by their communities. Example: Infispan Operator
OperatorHub fetches the catalog data from an operator installed by default on all clusters called Marketplace Operator.
The value of the field
disableAllDefaultSources needs to be
false in the CR called
cluster to view the operator’s catalog.
Installing an Operator from OperatorHub
OperatorHub is accessible from Operators -> OperatorHub on the web UI of the OpenShift cluster.
To install an operator you can just click the Install button and it will present options to select an update channel (version of the operator), installation mode (specific or all namespaces), and update approval (automatic or manual).
Once installed the operator should be visible in Operators -> Installed Operators.
Operator Framework is a set of developer tools for operators, it includes:
- Operator Lifecycle Manager (OLM): Handles installation, update, and management of operators on the cluster.
- Operator SDK: SDK for building operators using Ansible, Helm Chart, or Go.
- Operator Registry: Registry of operators that could be hosted on an OpenShift cluster.
To explore other projects under Operator Framework you can check their GitHub.
Operator Lifecycle Manager (OLM)
The Operator Lifecycle Manager (OLM) is installed by default on OpenShift clusters. It ensures:
- The dependencies of an operator (including other operators) are satisfied before its installation.
- Installed operators are up-to-date.
- Availability of the operators to the users of the cluster.
- There are no conflicts between multiple operator installations.
- Installed operators are accessible through UI, API, and CLI.
The OLM itself consists of two operators: OLM Operator and Catalog Operator.
The OLM Operator deploys the resources defined in
ClusterServiceVersion present on the namespace.
CSV represents a specific version of an operator. It contains operator metadata such as its name, description, version, details of the maintainer, installation strategy, and APIs provided by the operator.
OLM has cluster-admin privileges. Operators could request some of these cluster-admin permissions in their
CSV. By creating an
OperatorGroup the cluster administrator can take control of the permissions granted to the operators or limit them to one or more namespaces.
Operators can modify the OLM’s management strategy by stating their conditions in
OperatorCondition. For example, an operator could set the
status for the Upgradable property to
False if its installation has to be frozen on a specific version.
Catalog Operator installs the operator based on
InstallPlan. It also updates the operator if a new version is available on its
CatalogSource is a metadata store for discovering and installing operators.
Subscription specifies the
CatalogSource to be referenced by OLM during installation and updates. The channel (alpha/beta/stable) of the operator could also be specified in the
InstallPlan defines the operator’s custom resources to be installed.
Installing a Specific Version of the Operator
By default, OpenShift installs the latest available version of an operator in the
CatalogSource. If you want to change this behavior and install a specific version of the operator you have to edit its
Subscription and specify the version to be installed in
startingCSV and set
Note that if the required version is not available on the default
channel then you have to change it as well.
Example of a
Subscription for installing v1.9.0 of OpenShift Pipelines Operator
If an update is available in the future the operator’s
InstallPlan has to be approved manually, this will prevent automatic updates.
Uninstalling an Operator
The option to uninstall an operator is present in its Actions on UI.
To uninstall an operator from CLI, you have to remove its
Subscription as well as its
ClusterServiceVersion using the
delete subcommand on the specific resources.
# Listing available subscriptions
$ oc get subscriptions -n openshift-operators
NAME PACKAGE SOURCE
openshift-pipelines-operator-rh openshift-pipelines-operator-rh redhat-operators
# Deleting subscription for OpenShift Pipelines Operator
$ oc delete subscription/openshift-pipelines-operator-rh -n openshift-operators
# Listing available clusterserviceversions
$ oc get clusterserviceversions -n openshift-operators
NAME DISPLAY VERSION
openshift-pipelines-operator-rh.v1.10.0 Red Hat OpenShift Pipelines 1.10.0
# Deleting clusterserviceversion for OpenShift Pipelines Operator
$ oc delete csv/openshift-pipelines-operator-rh.v1.10.0 -n openshift-operators
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