When you submit a support case to Red Hat Support, it is helpful to provide debugging information for OpenShift Container Platform and OpenShift Virtualization by using the following tools:

must-gather tool

The must-gather tool collects diagnostic information, including resource definitions and service logs.


Prometheus is a time-series database and a rule evaluation engine for metrics. Prometheus sends alerts to Alertmanager for processing.


The Alertmanager service handles alerts received from Prometheus. The Alertmanager is also responsible for sending the alerts to external notification systems.

Collecting data about your environment

Collecting data about your environment minimizes the time required to analyze and determine the root cause.

  • Set the retention time for Prometheus metrics data to a minimum of seven days.

  • Configure the Alertmanager to capture relevant alerts and to send them to a dedicated mailbox so that they can be viewed and persisted outside the cluster.

  • Record the exact number of affected nodes and virtual machines.

  1. Collect must-gather data for the cluster by using the default must-gather image.

  2. Collect must-gather data for Red Hat OpenShift Container Storage, if necessary.

  3. Collect must-gather data for OpenShift Virtualization by using the OpenShift Virtualization must-gather image.

  4. Collect Prometheus metrics for the cluster.

Additional resources

Collecting data about virtual machines

Collecting data about malfunctioning virtual machines (VMs) minimizes the time required to analyze and determine the root cause.

  • Windows VMs:

    • Record the Windows patch update details for Red Hat Support.

    • Install the latest version of the VirtIO drivers. The VirtIO drivers include the QEMU guest agent.

    • If Remote Desktop Protocol (RDP) is enabled, try to connect to the VMs with RDP to determine whether there is a problem with the connection software.

  1. Collect detailed must-gather data about the malfunctioning VMs.

  2. Collect screenshots of VMs that have crashed before you restart them.

  3. Record factors that the malfunctioning VMs have in common. For example, the VMs have the same host or network.

Additional resources

Using the must-gather tool for OpenShift Virtualization

You can collect data about OpenShift Virtualization resources by running the must-gather command with the OpenShift Virtualization image.

The default data collection includes information about the following resources:

  • OpenShift Virtualization Operator namespaces, including child objects

  • OpenShift Virtualization custom resource definitions

  • Namespaces that contain virtual machines

  • Basic virtual machine definitions

  • Run the following command to collect data about OpenShift Virtualization:

    $ oc adm must-gather --image-stream=openshift/must-gather \

must-gather tool options

You can specify a combination of scripts and environment variables for the following options:

  • Collecting detailed virtual machine (VM) information from a namespace

  • Collecting detailed information about specified VMs

  • Collecting image and image stream information

  • Limiting the maximum number of parallel processes used by the must-gather tool


Environment variables

You can specify environment variables for a compatible script.


Collect virtual machine information, including virt-launcher pod details, from the namespace that you specify. The VirtualMachine and VirtualMachineInstance CR data is collected for all namespaces.


Collect details about a particular virtual machine. To use this option, you must also specify a namespace by using the NS environment variable.


Modify the maximum number of parallel processes that the must-gather tool uses. The default value is 5.

Using too many parallel processes can cause performance issues. Increasing the maximum number of parallel processes is not recommended.


Each script is only compatible with certain environment variable combinations.


Collect VM log files, VM definitions, and namespaces (and their child objects) that belong to OpenShift Virtualization resources. If you use this parameter without specifying a namespace or VM, the must-gather tool collects this data for all VMs in the cluster. This script is compatible with all environment variables, but you must specify a namespace if you use the VM variable.


Use the default must-gather script, which collects cluster data from all namespaces and includes only basic VM information. This script is only compatible with the PROS variable.


Collect image and image stream custom resource information. This script is only compatible with the PROS variable.

Usage and examples

Environment variables are optional. You can run a script by itself or with one or more compatible environment variables.

Table 1. Compatible parameters
Script Compatible environment variable


  • For a namespace: NS=<namespace_name>

  • For a VM: VM=<vm_name> NS=<namespace_name>

  • PROS=<number_of_processes>


  • PROS=<number_of_processes>


  • PROS=<number_of_processes>

To customize the data that must-gather collects, you append a double dash (--) to the command, followed by a space and one or more compatible parameters.

$ oc adm must-gather \
  --image=registry.redhat.io/container-native-virtualization/cnv-must-gather-rhel8:v4.8.7 \
  -- <environment_variable_1> <environment_variable_2> <script_name>
Detailed VM information

The following command collects detailed VM information for the my-vm VM in the mynamespace namespace:

$ oc adm must-gather \
  --image=registry.redhat.io/container-native-virtualization/cnv-must-gather-rhel8:v4.8.7 \
  -- NS=mynamespace VM=my-vm gather_vms_details (1)
1 The NS environment variable is mandatory if you use the VM environment variable.
Default data collection limited to three parallel processes

The following command collects default must-gather information by using a maximum of three parallel processes:

$ oc adm must-gather \
  --image=registry.redhat.io/container-native-virtualization/cnv-must-gather-rhel8:v4.8.7 \
  -- PROS=3 gather
Image and image stream information

The following command collects image and image stream information from the cluster:

$ oc adm must-gather \
  --image=registry.redhat.io/container-native-virtualization/cnv-must-gather-rhel8:v4.8.7 \
  -- gather_images

Additional resources