Troubleshooting | Migrating from version 3 to 4

MTC workflow
Migration Toolkit for Containers custom resource manifests
Logs and debugging tools
Common issues and concerns
Rolling back a migration

This section describes resources for troubleshooting the Migration Toolkit for Containers (MTC).

For known issues, see the MTC release notes.

MTC workflow

You can migrate Kubernetes resources, persistent volume data, and internal container images to OKD 4.15 by using the Migration Toolkit for Containers (MTC) web console or the Kubernetes API.

MTC migrates the following resources:

A namespace specified in a migration plan.
Namespace-scoped resources: When the MTC migrates a namespace, it migrates all the objects and resources associated with that namespace, such as services or pods. Additionally, if a resource that exists in the namespace but not at the cluster level depends on a resource that exists at the cluster level, the MTC migrates both resources.

For example, a security context constraint (SCC) is a resource that exists at the cluster level and a service account (SA) is a resource that exists at the namespace level. If an SA exists in a namespace that the MTC migrates, the MTC automatically locates any SCCs that are linked to the SA and also migrates those SCCs. Similarly, the MTC migrates persistent volumes that are linked to the persistent volume claims of the namespace.

Cluster-scoped resources might have to be migrated manually, depending on the resource.
Custom resources (CRs) and custom resource definitions (CRDs): MTC automatically migrates CRs and CRDs at the namespace level.

Migrating an application with the MTC web console involves the following steps:

Install the Migration Toolkit for Containers Operator on all clusters.

You can install the Migration Toolkit for Containers Operator in a restricted environment with limited or no internet access. The source and target clusters must have network access to each other and to a mirror registry.
Configure the replication repository, an intermediate object storage that MTC uses to migrate data.

The source and target clusters must have network access to the replication repository during migration. If you are using a proxy server, you must configure it to allow network traffic between the replication repository and the clusters.
Add the source cluster to the MTC web console.
Add the replication repository to the MTC web console.
Create a migration plan, with one of the following data migration options:
- Copy: MTC copies the data from the source cluster to the replication repository, and from the replication repository to the target cluster.
  
  If you are using direct image migration or direct volume migration, the images or volumes are copied directly from the source cluster to the target cluster.
- Move: MTC unmounts a remote volume, for example, NFS, from the source cluster, creates a PV resource on the target cluster pointing to the remote volume, and then mounts the remote volume on the target cluster. Applications running on the target cluster use the same remote volume that the source cluster was using. The remote volume must be accessible to the source and target clusters.
  
  Although the replication repository does not appear in this diagram, it is required for migration.
Run the migration plan, with one of the following options:
- Stage copies data to the target cluster without stopping the application.
  
  A stage migration can be run multiple times so that most of the data is copied to the target before migration. Running one or more stage migrations reduces the duration of the cutover migration.
- Cutover stops the application on the source cluster and moves the resources to the target cluster.
  
  Optional: You can clear the Halt transactions on the source cluster during migration checkbox.

About MTC custom resources

The Migration Toolkit for Containers (MTC) creates the following custom resources (CRs):

MigCluster (configuration, MTC cluster): Cluster definition

MigStorage (configuration, MTC cluster): Storage definition

MigPlan (configuration, MTC cluster): Migration plan

The MigPlan CR describes the source and target clusters, replication repository, and namespaces being migrated. It is associated with 0, 1, or many MigMigration CRs.

Deleting a MigPlan CR deletes the associated MigMigration CRs.

BackupStorageLocation (configuration, MTC cluster): Location of Velero backup objects

VolumeSnapshotLocation (configuration, MTC cluster): Location of Velero volume snapshots

MigMigration (action, MTC cluster): Migration, created every time you stage or migrate data. Each MigMigration CR is associated with a MigPlan CR.

Backup (action, source cluster): When you run a migration plan, the MigMigration CR creates two Velero backup CRs on each source cluster:

Backup CR #1 for Kubernetes objects
Backup CR #2 for PV data

Restore (action, target cluster): When you run a migration plan, the MigMigration CR creates two Velero restore CRs on the target cluster:

Restore CR #1 (using Backup CR #2) for PV data
Restore CR #2 (using Backup CR #1) for Kubernetes objects

Migration Toolkit for Containers custom resource manifests

Migration Toolkit for Containers (MTC) uses the following custom resource (CR) manifests for migrating applications.

DirectImageMigration

The DirectImageMigration CR copies images directly from the source cluster to the destination cluster.

apiVersion: migration.openshift.io/v1alpha1
kind: DirectImageMigration
metadata:
  labels:
    controller-tools.k8s.io: "1.0"
  name: <direct_image_migration>
spec:
  srcMigClusterRef:
    name: <source_cluster>
    namespace: openshift-migration
  destMigClusterRef:
    name: <destination_cluster>
    namespace: openshift-migration
  namespaces: (1)
    - <source_namespace_1>
    - <source_namespace_2>:<destination_namespace_3> (2)

1	One or more namespaces containing images to be migrated. By default, the destination namespace has the same name as the source namespace.
2	Source namespace mapped to a destination namespace with a different name.

DirectImageStreamMigration

The DirectImageStreamMigration CR copies image stream references directly from the source cluster to the destination cluster.

apiVersion: migration.openshift.io/v1alpha1
kind: DirectImageStreamMigration
metadata:
  labels:
    controller-tools.k8s.io: "1.0"
  name: <direct_image_stream_migration>
spec:
  srcMigClusterRef:
    name: <source_cluster>
    namespace: openshift-migration
  destMigClusterRef:
    name: <destination_cluster>
    namespace: openshift-migration
  imageStreamRef:
    name: <image_stream>
    namespace: <source_image_stream_namespace>
  destNamespace: <destination_image_stream_namespace>

DirectVolumeMigration

The DirectVolumeMigration CR copies persistent volumes (PVs) directly from the source cluster to the destination cluster.

apiVersion: migration.openshift.io/v1alpha1
kind: DirectVolumeMigration
metadata:
  name: <direct_volume_migration>
  namespace: openshift-migration
spec:
  createDestinationNamespaces: false (1)
  deleteProgressReportingCRs: false (2)
  destMigClusterRef:
    name: <host_cluster> (3)
    namespace: openshift-migration
  persistentVolumeClaims:
  - name: <pvc> (4)
    namespace: <pvc_namespace>
  srcMigClusterRef:
    name: <source_cluster>
    namespace: openshift-migration

1	Set to `true` to create namespaces for the PVs on the destination cluster.
2	Set to `true` to delete `DirectVolumeMigrationProgress` CRs after migration. The default is `false` so that `DirectVolumeMigrationProgress` CRs are retained for troubleshooting.
3	Update the cluster name if the destination cluster is not the host cluster.
4	Specify one or more PVCs to be migrated.

DirectVolumeMigrationProgress

The DirectVolumeMigrationProgress CR shows the progress of the DirectVolumeMigration CR.

apiVersion: migration.openshift.io/v1alpha1
kind: DirectVolumeMigrationProgress
metadata:
  labels:
    controller-tools.k8s.io: "1.0"
  name: <direct_volume_migration_progress>
spec:
  clusterRef:
    name: <source_cluster>
    namespace: openshift-migration
  podRef:
    name: <rsync_pod>
    namespace: openshift-migration

MigAnalytic

The MigAnalytic CR collects the number of images, Kubernetes resources, and the persistent volume (PV) capacity from an associated MigPlan CR.

You can configure the data that it collects.

apiVersion: migration.openshift.io/v1alpha1
kind: MigAnalytic
metadata:
  annotations:
    migplan: <migplan>
  name: <miganalytic>
  namespace: openshift-migration
  labels:
    migplan: <migplan>
spec:
  analyzeImageCount: true (1)
  analyzeK8SResources: true (2)
  analyzePVCapacity: true (3)
  listImages: false (4)
  listImagesLimit: 50 (5)
  migPlanRef:
    name: <migplan>
    namespace: openshift-migration

1	Optional: Returns the number of images.
2	Optional: Returns the number, kind, and API version of the Kubernetes resources.
3	Optional: Returns the PV capacity.
4	Returns a list of image names. The default is `false` so that the output is not excessively long.
5	Optional: Specify the maximum number of image names to return if `listImages` is `true`.

MigCluster

The MigCluster CR defines a host, local, or remote cluster.

apiVersion: migration.openshift.io/v1alpha1
kind: MigCluster
metadata:
  labels:
    controller-tools.k8s.io: "1.0"
  name: <host_cluster> (1)
  namespace: openshift-migration
spec:
  isHostCluster: true (2)
# The 'azureResourceGroup' parameter is relevant only for Microsoft Azure.
  azureResourceGroup: <azure_resource_group> (3)
  caBundle: <ca_bundle_base64> (4)
  insecure: false (5)
  refresh: false (6)
# The 'restartRestic' parameter is relevant for a source cluster.
  restartRestic: true (7)
# The following parameters are relevant for a remote cluster.
  exposedRegistryPath: <registry_route> (8)
  url: <destination_cluster_url> (9)
  serviceAccountSecretRef:
    name: <source_secret> (10)
    namespace: openshift-config

1	Update the cluster name if the `migration-controller` pod is not running on this cluster.
2	The `migration-controller` pod runs on this cluster if `true`.
3	Microsoft Azure only: Specify the resource group.
4	Optional: If you created a certificate bundle for self-signed CA certificates and if the `insecure` parameter value is `false`, specify the base64-encoded certificate bundle.
5	Set to `true` to disable SSL verification.
6	Set to `true` to validate the cluster.
7	Set to `true` to restart the `Restic` pods on the source cluster after the `Stage` pods are created.
8	Remote cluster and direct image migration only: Specify the exposed secure registry path.
9	Remote cluster only: Specify the URL.
10	Remote cluster only: Specify the name of the `Secret` object.

MigHook

The MigHook CR defines a migration hook that runs custom code at a specified stage of the migration. You can create up to four migration hooks. Each hook runs during a different phase of the migration.

You can configure the hook name, runtime duration, a custom image, and the cluster where the hook will run.

The migration phases and namespaces of the hooks are configured in the MigPlan CR.

apiVersion: migration.openshift.io/v1alpha1
kind: MigHook
metadata:
  generateName: <hook_name_prefix> (1)
  name: <mighook> (2)
  namespace: openshift-migration
spec:
  activeDeadlineSeconds: 1800 (3)
  custom: false (4)
  image: <hook_image> (5)
  playbook: <ansible_playbook_base64> (6)
  targetCluster: source (7)

1	Optional: A unique hash is appended to the value for this parameter so that each migration hook has a unique name. You do not need to specify the value of the `name` parameter.
2	Specify the migration hook name, unless you specify the value of the `generateName` parameter.
3	Optional: Specify the maximum number of seconds that a hook can run. The default is `1800`.
4	The hook is a custom image if `true`. The custom image can include Ansible or it can be written in a different programming language.
5	Specify the custom image, for example, `quay.io/konveyor/hook-runner:latest`. Required if `custom` is `true`.
6	Base64-encoded Ansible playbook. Required if `custom` is `false`.
7	Specify the cluster on which the hook will run. Valid values are `source` or `destination`.

MigMigration

The MigMigration CR runs a MigPlan CR.

You can configure a Migmigration CR to run a stage or incremental migration, to cancel a migration in progress, or to roll back a completed migration.

apiVersion: migration.openshift.io/v1alpha1
kind: MigMigration
metadata:
  labels:
    controller-tools.k8s.io: "1.0"
  name: <migmigration>
  namespace: openshift-migration
spec:
  canceled: false (1)
  rollback: false (2)
  stage: false (3)
  quiescePods: true (4)
  keepAnnotations: true (5)
  verify: false (6)
  migPlanRef:
    name: <migplan>
    namespace: openshift-migration

1	Set to `true` to cancel a migration in progress.
2	Set to `true` to roll back a completed migration.
3	Set to `true` to run a stage migration. Data is copied incrementally and the pods on the source cluster are not stopped.
4	Set to `true` to stop the application during migration. The pods on the source cluster are scaled to `0` after the `Backup` stage.
5	Set to `true` to retain the labels and annotations applied during the migration.
6	Set to `true` to check the status of the migrated pods on the destination cluster are checked and to return the names of pods that are not in a `Running` state.

MigPlan

The MigPlan CR defines the parameters of a migration plan.

You can configure destination namespaces, hook phases, and direct or indirect migration.

By default, a destination namespace has the same name as the source namespace. If you configure a different destination namespace, you must ensure that the namespaces are not duplicated on the source or the destination clusters because the UID and GID ranges are copied during migration.

apiVersion: migration.openshift.io/v1alpha1
kind: MigPlan
metadata:
  labels:
    controller-tools.k8s.io: "1.0"
  name: <migplan>
  namespace: openshift-migration
spec:
  closed: false (1)
  srcMigClusterRef:
    name: <source_cluster>
    namespace: openshift-migration
  destMigClusterRef:
    name: <destination_cluster>
    namespace: openshift-migration
  hooks: (2)
    - executionNamespace: <namespace> (3)
      phase: <migration_phase> (4)
      reference:
        name: <hook> (5)
        namespace: <hook_namespace> (6)
      serviceAccount: <service_account> (7)
  indirectImageMigration: true (8)
  indirectVolumeMigration: false (9)
  migStorageRef:
    name: <migstorage>
    namespace: openshift-migration
  namespaces:
    - <source_namespace_1> (10)
    - <source_namespace_2>
    - <source_namespace_3>:<destination_namespace_4> (11)
  refresh: false  (12)

1	The migration has completed if `true`. You cannot create another `MigMigration` CR for this `MigPlan` CR.
2	Optional: You can specify up to four migration hooks. Each hook must run during a different migration phase.
3	Optional: Specify the namespace in which the hook will run.
4	Optional: Specify the migration phase during which a hook runs. One hook can be assigned to one phase. Valid values are `PreBackup`, `PostBackup`, `PreRestore`, and `PostRestore`.
5	Optional: Specify the name of the `MigHook` CR.
6	Optional: Specify the namespace of `MigHook` CR.
7	Optional: Specify a service account with `cluster-admin` privileges.
8	Direct image migration is disabled if `true`. Images are copied from the source cluster to the replication repository and from the replication repository to the destination cluster.
9	Direct volume migration is disabled if `true`. PVs are copied from the source cluster to the replication repository and from the replication repository to the destination cluster.
10	Specify one or more source namespaces. If you specify only the source namespace, the destination namespace is the same.
11	Specify the destination namespace if it is different from the source namespace.
12	The `MigPlan` CR is validated if `true`.

MigStorage

The MigStorage CR describes the object storage for the replication repository.

Amazon Web Services (AWS), Microsoft Azure, Google Cloud Storage, Multi-Cloud Object Gateway, and generic S3-compatible cloud storage are supported.

AWS and the snapshot copy method have additional parameters.

apiVersion: migration.openshift.io/v1alpha1
kind: MigStorage
metadata:
  labels:
    controller-tools.k8s.io: "1.0"
  name: <migstorage>
  namespace: openshift-migration
spec:
  backupStorageProvider: <backup_storage_provider> (1)
  volumeSnapshotProvider: <snapshot_storage_provider> (2)
  backupStorageConfig:
    awsBucketName: <bucket> (3)
    awsRegion: <region> (4)
    credsSecretRef:
      namespace: openshift-config
      name: <storage_secret> (5)
    awsKmsKeyId: <key_id> (6)
    awsPublicUrl: <public_url> (7)
    awsSignatureVersion: <signature_version> (8)
  volumeSnapshotConfig:
    awsRegion: <region> (9)
    credsSecretRef:
      namespace: openshift-config
      name: <storage_secret> (10)
  refresh: false (11)

1	Specify the storage provider.
2	Snapshot copy method only: Specify the storage provider.
3	AWS only: Specify the bucket name.
4	AWS only: Specify the bucket region, for example, `us-east-1`.
5	Specify the name of the `Secret` object that you created for the storage.
6	AWS only: If you are using the AWS Key Management Service, specify the unique identifier of the key.
7	AWS only: If you granted public access to the AWS bucket, specify the bucket URL.
8	AWS only: Specify the AWS signature version for authenticating requests to the bucket, for example, `4`.
9	Snapshot copy method only: Specify the geographical region of the clusters.
10	Snapshot copy method only: Specify the name of the `Secret` object that you created for the storage.
11	Set to `true` to validate the cluster.

Logs and debugging tools

This section describes logs and debugging tools that you can use for troubleshooting.

Viewing migration plan resources

You can view migration plan resources to monitor a running migration or to troubleshoot a failed migration by using the MTC web console and the command line interface (CLI).

Procedure

In the MTC web console, click Migration Plans.
Click the Migrations number next to a migration plan to view the Migrations page.
Click a migration to view the Migration details.
Expand Migration resources to view the migration resources and their status in a tree view.

To troubleshoot a failed migration, start with a high-level resource that has failed and then work down the resource tree towards the lower-level resources.
Click the Options menu next to a resource and select one of the following options:
- Copy oc describe command copies the command to your clipboard.
  - Log in to the relevant cluster and then run the command.
    
    The conditions and events of the resource are displayed in YAML format.
- Copy oc logs command copies the command to your clipboard.
  - Log in to the relevant cluster and then run the command.
    
    If the resource supports log filtering, a filtered log is displayed.
- View JSON displays the resource data in JSON format in a web browser.
  
  The data is the same as the output for the oc get <resource> command.

Viewing a migration plan log

You can view an aggregated log for a migration plan. You use the MTC web console to copy a command to your clipboard and then run the command from the command line interface (CLI).

The command displays the filtered logs of the following pods:

Migration Controller
Velero
Restic
Rsync
Stunnel
Registry

Procedure

In the MTC web console, click Migration Plans.
Click the Migrations number next to a migration plan.
Click View logs.
Click the Copy icon to copy the oc logs command to your clipboard.
Log in to the relevant cluster and enter the command on the CLI.

The aggregated log for the migration plan is displayed.

Using the migration log reader

You can use the migration log reader to display a single filtered view of all the migration logs.

Procedure

Get the mig-log-reader pod:

$ oc -n openshift-migration get pods | grep log

Enter the following command to display a single migration log:
```
$ oc -n openshift-migration logs -f <mig-log-reader-pod> -c color (1)
```
1 The -c plain option displays the log without colors.

Accessing performance metrics

The MigrationController custom resource (CR) records metrics and pulls them into on-cluster monitoring storage. You can query the metrics by using Prometheus Query Language (PromQL) to diagnose migration performance issues. All metrics are reset when the Migration Controller pod restarts.

You can access the performance metrics and run queries by using the OKD web console.

Procedure

In the OKD web console, click Observe → Metrics.
Enter a PromQL query, select a time window to display, and click Run Queries.

If your web browser does not display all the results, use the Prometheus console.

Provided metrics

The MigrationController custom resource (CR) provides metrics for the MigMigration CR count and for its API requests.

cam_app_workload_migrations

This metric is a count of MigMigration CRs over time. It is useful for viewing alongside the mtc_client_request_count and mtc_client_request_elapsed metrics to collate API request information with migration status changes. This metric is included in Telemetry.

Table 1. cam_app_workload_migrations metric
Queryable label name	Sample label values	Label description
status	`running`, `idle`, `failed`, `completed`	Status of the `MigMigration` CR
type	stage, final	Type of the `MigMigration` CR

mtc_client_request_count

This metric is a cumulative count of Kubernetes API requests that MigrationController issued. It is not included in Telemetry.

Table 2. mtc_client_request_count metric
Queryable label name	Sample label values	Label description
cluster	`https://migcluster-url:443`	Cluster that the request was issued against
component	`MigPlan`, `MigCluster`	Sub-controller API that issued request
function	`(*ReconcileMigPlan).Reconcile`	Function that the request was issued from
kind	`SecretList`, `Deployment`	Kubernetes kind the request was issued for

mtc_client_request_elapsed

This metric is a cumulative latency, in milliseconds, of Kubernetes API requests that MigrationController issued. It is not included in Telemetry.

Table 3. mtc_client_request_elapsed metric
Queryable label name	Sample label values	Label description
cluster	`https://cluster-url.com:443`	Cluster that the request was issued against
component	`migplan`, `migcluster`	Sub-controller API that issued request
function	`(*ReconcileMigPlan).Reconcile`	Function that the request was issued from
kind	`SecretList`, `Deployment`	Kubernetes resource that the request was issued for

Useful queries

The table lists some helpful queries that can be used for monitoring performance.

Table 4. Useful queries
Query	Description
`mtc_client_request_count`	Number of API requests issued, sorted by request type
`sum(mtc_client_request_count)`	Total number of API requests issued
`mtc_client_request_elapsed`	API request latency, sorted by request type
`sum(mtc_client_request_elapsed)`	Total latency of API requests
`sum(mtc_client_request_elapsed) / sum(mtc_client_request_count)`	Average latency of API requests
`mtc_client_request_elapsed / mtc_client_request_count`	Average latency of API requests, sorted by request type
`cam_app_workload_migrations{status="running"} * 100`	Count of running migrations, multiplied by 100 for easier viewing alongside request counts

Using the must-gather tool

You can collect logs, metrics, and information about MTC custom resources by using the must-gather tool.

The must-gather data must be attached to all customer cases.

You can collect data for a one-hour or a 24-hour period and view the data with the Prometheus console.

Prerequisites

You must be logged in to the OKD cluster as a user with the cluster-admin role.
You must have the OpenShift CLI (oc) installed.

Procedure

Navigate to the directory where you want to store the must-gather data.
Run the oc adm must-gather command for one of the following data collection options:
- To collect data for the past hour, run the following command:
  $ oc adm must-gather --image=registry.redhat.io/rhmtc/openshift-migration-must-gather-rhel8:v1.7
  This command saves the data as the must-gather/must-gather.tar.gz file. You can upload this file to a support case on the Red Hat Customer Portal.
- To collect data for the past 24 hours, run the following command:
  $ oc adm must-gather --image=registry.redhat.io/rhmtc/openshift-migration-must-gather-rhel8:v1.7 -- /usr/bin/gather_metrics_dump
  This operation can take a long time. This command saves the data as the must-gather/metrics/prom_data.tar.gz file.

Debugging Velero resources with the Velero CLI tool

You can debug Backup and Restore custom resources (CRs) and retrieve logs with the Velero CLI tool.

The Velero CLI tool provides more detailed information than the OpenShift CLI tool.

Syntax

Use the oc exec command to run a Velero CLI command:

$ oc -n openshift-migration exec deployment/velero -c velero -- ./velero \
  <backup_restore_cr> <command> <cr_name>

Example

$ oc -n openshift-migration exec deployment/velero -c velero -- ./velero \
  backup describe 0e44ae00-5dc3-11eb-9ca8-df7e5254778b-2d8ql

Help option

Use the velero --help option to list all Velero CLI commands:

$ oc -n openshift-migration exec deployment/velero -c velero -- ./velero \
  --help

Describe command

Use the velero describe command to retrieve a summary of warnings and errors associated with a Backup or Restore CR:

$ oc -n openshift-migration exec deployment/velero -c velero -- ./velero \
  <backup_restore_cr> describe <cr_name>

Example

$ oc -n openshift-migration exec deployment/velero -c velero -- ./velero \
  backup describe 0e44ae00-5dc3-11eb-9ca8-df7e5254778b-2d8ql

The following types of restore errors and warnings are shown in the output of a velero describe request:

Velero: A list of messages related to the operation of Velero itself, for example, messages related to connecting to the cloud, reading a backup file, and so on
Cluster: A list of messages related to backing up or restoring cluster-scoped resources
Namespaces: A list of list of messages related to backing up or restoring resources stored in namespaces

One or more errors in one of these categories results in a Restore operation receiving the status of PartiallyFailed and not Completed. Warnings do not lead to a change in the completion status.

For resource-specific errors, that is, Cluster and Namespaces errors, the restore describe --details output includes a resource list that lists all resources that Velero succeeded in restoring. For any resource that has such an error, check to see if the resource is actually in the cluster.
If there are Velero errors, but no resource-specific errors, in the output of a describe command, it is possible that the restore completed without any actual problems in restoring workloads, but carefully validate post-restore applications.

For example, if the output contains PodVolumeRestore or node agent-related errors, check the status of PodVolumeRestores and DataDownloads. If none of these are failed or still running, then volume data might have been fully restored.

Logs command

Use the velero logs command to retrieve the logs of a Backup or Restore CR:

$ oc -n openshift-migration exec deployment/velero -c velero -- ./velero \
  <backup_restore_cr> logs <cr_name>

Example

$ oc -n openshift-migration exec deployment/velero -c velero -- ./velero \
  restore logs ccc7c2d0-6017-11eb-afab-85d0007f5a19-x4lbf

Debugging a partial migration failure

You can debug a partial migration failure warning message by using the Velero CLI to examine the Restore custom resource (CR) logs.

A partial failure occurs when Velero encounters an issue that does not cause a migration to fail. For example, if a custom resource definition (CRD) is missing or if there is a discrepancy between CRD versions on the source and target clusters, the migration completes but the CR is not created on the target cluster.

Velero logs the issue as a partial failure and then processes the rest of the objects in the Backup CR.

Procedure

Check the status of a MigMigration CR:

$ oc get migmigration <migmigration> -o yaml

Example output

status:
  conditions:
  - category: Warn
    durable: true
    lastTransitionTime: "2021-01-26T20:48:40Z"
    message: 'Final Restore openshift-migration/ccc7c2d0-6017-11eb-afab-85d0007f5a19-x4lbf: partially failed on destination cluster'
    status: "True"
    type: VeleroFinalRestorePartiallyFailed
  - category: Advisory
    durable: true
    lastTransitionTime: "2021-01-26T20:48:42Z"
    message: The migration has completed with warnings, please look at `Warn` conditions.
    reason: Completed
    status: "True"
    type: SucceededWithWarnings

Check the status of the Restore CR by using the Velero describe command:

$ oc -n {namespace} exec deployment/velero -c velero -- ./velero \
  restore describe <restore>

Example output

Phase:  PartiallyFailed (run 'velero restore logs ccc7c2d0-6017-11eb-afab-85d0007f5a19-x4lbf' for more information)

Errors:
  Velero:     <none>
  Cluster:    <none>
  Namespaces:
    migration-example:  error restoring example.com/migration-example/migration-example: the server could not find the requested resource

Check the Restore CR logs by using the Velero logs command:

$ oc -n {namespace} exec deployment/velero -c velero -- ./velero \
  restore logs <restore>

Example output

time="2021-01-26T20:48:37Z" level=info msg="Attempting to restore migration-example: migration-example" logSource="pkg/restore/restore.go:1107" restore=openshift-migration/ccc7c2d0-6017-11eb-afab-85d0007f5a19-x4lbf
time="2021-01-26T20:48:37Z" level=info msg="error restoring migration-example: the server could not find the requested resource" logSource="pkg/restore/restore.go:1170" restore=openshift-migration/ccc7c2d0-6017-11eb-afab-85d0007f5a19-x4lbf

The Restore CR log error message, the server could not find the requested resource, indicates the cause of the partially failed migration.

Using MTC custom resources for troubleshooting

You can check the following Migration Toolkit for Containers (MTC) custom resources (CRs) to troubleshoot a failed migration:

MigCluster
MigStorage
MigPlan
BackupStorageLocation

The BackupStorageLocation CR contains a migrationcontroller label to identify the MTC instance that created the CR:
```
    labels:
      migrationcontroller: ebe13bee-c803-47d0-a9e9-83f380328b93
```
VolumeSnapshotLocation

The VolumeSnapshotLocation CR contains a migrationcontroller label to identify the MTC instance that created the CR:
```
    labels:
      migrationcontroller: ebe13bee-c803-47d0-a9e9-83f380328b93
```
MigMigration
Backup

MTC changes the reclaim policy of migrated persistent volumes (PVs) to Retain on the target cluster. The Backup CR contains an openshift.io/orig-reclaim-policy annotation that indicates the original reclaim policy. You can manually restore the reclaim policy of the migrated PVs.
Restore

Procedure

List the MigMigration CRs in the openshift-migration namespace:

$ oc get migmigration -n openshift-migration

Example output

NAME                                   AGE
88435fe0-c9f8-11e9-85e6-5d593ce65e10   6m42s

Inspect the MigMigration CR:

$ oc describe migmigration 88435fe0-c9f8-11e9-85e6-5d593ce65e10 -n openshift-migration

The output is similar to the following examples.

MigMigration example output

name:         88435fe0-c9f8-11e9-85e6-5d593ce65e10
namespace:    openshift-migration
labels:       <none>
annotations:  touch: 3b48b543-b53e-4e44-9d34-33563f0f8147
apiVersion:  migration.openshift.io/v1alpha1
kind:         MigMigration
metadata:
  creationTimestamp:  2019-08-29T01:01:29Z
  generation:          20
  resourceVersion:    88179
  selfLink:           /apis/migration.openshift.io/v1alpha1/namespaces/openshift-migration/migmigrations/88435fe0-c9f8-11e9-85e6-5d593ce65e10
  uid:                 8886de4c-c9f8-11e9-95ad-0205fe66cbb6
spec:
  migPlanRef:
    name:        socks-shop-mig-plan
    namespace:   openshift-migration
  quiescePods:  true
  stage:         false
status:
  conditions:
    category:              Advisory
    durable:               True
    lastTransitionTime:  2019-08-29T01:03:40Z
    message:               The migration has completed successfully.
    reason:                Completed
    status:                True
    type:                  Succeeded
  phase:                   Completed
  startTimestamp:         2019-08-29T01:01:29Z
events:                    <none>

Velero backup CR #2 example output that describes the PV data

apiVersion: velero.io/v1
kind: Backup
metadata:
  annotations:
    openshift.io/migrate-copy-phase: final
    openshift.io/migrate-quiesce-pods: "true"
    openshift.io/migration-registry: 172.30.105.179:5000
    openshift.io/migration-registry-dir: /socks-shop-mig-plan-registry-44dd3bd5-c9f8-11e9-95ad-0205fe66cbb6
    openshift.io/orig-reclaim-policy: delete
  creationTimestamp: "2019-08-29T01:03:15Z"
  generateName: 88435fe0-c9f8-11e9-85e6-5d593ce65e10-
  generation: 1
  labels:
    app.kubernetes.io/part-of: migration
    migmigration: 8886de4c-c9f8-11e9-95ad-0205fe66cbb6
    migration-stage-backup: 8886de4c-c9f8-11e9-95ad-0205fe66cbb6
    velero.io/storage-location: myrepo-vpzq9
  name: 88435fe0-c9f8-11e9-85e6-5d593ce65e10-59gb7
  namespace: openshift-migration
  resourceVersion: "87313"
  selfLink: /apis/velero.io/v1/namespaces/openshift-migration/backups/88435fe0-c9f8-11e9-85e6-5d593ce65e10-59gb7
  uid: c80dbbc0-c9f8-11e9-95ad-0205fe66cbb6
spec:
  excludedNamespaces: []
  excludedResources: []
  hooks:
    resources: []
  includeClusterResources: null
  includedNamespaces:
  - sock-shop
  includedResources:
  - persistentvolumes
  - persistentvolumeclaims
  - namespaces
  - imagestreams
  - imagestreamtags
  - secrets
  - configmaps
  - pods
  labelSelector:
    matchLabels:
      migration-included-stage-backup: 8886de4c-c9f8-11e9-95ad-0205fe66cbb6
  storageLocation: myrepo-vpzq9
  ttl: 720h0m0s
  volumeSnapshotLocations:
  - myrepo-wv6fx
status:
  completionTimestamp: "2019-08-29T01:02:36Z"
  errors: 0
  expiration: "2019-09-28T01:02:35Z"
  phase: Completed
  startTimestamp: "2019-08-29T01:02:35Z"
  validationErrors: null
  version: 1
  volumeSnapshotsAttempted: 0
  volumeSnapshotsCompleted: 0
  warnings: 0

Velero restore CR #2 example output that describes the Kubernetes resources

apiVersion: velero.io/v1
kind: Restore
metadata:
  annotations:
    openshift.io/migrate-copy-phase: final
    openshift.io/migrate-quiesce-pods: "true"
    openshift.io/migration-registry: 172.30.90.187:5000
    openshift.io/migration-registry-dir: /socks-shop-mig-plan-registry-36f54ca7-c925-11e9-825a-06fa9fb68c88
  creationTimestamp: "2019-08-28T00:09:49Z"
  generateName: e13a1b60-c927-11e9-9555-d129df7f3b96-
  generation: 3
  labels:
    app.kubernetes.io/part-of: migration
    migmigration: e18252c9-c927-11e9-825a-06fa9fb68c88
    migration-final-restore: e18252c9-c927-11e9-825a-06fa9fb68c88
  name: e13a1b60-c927-11e9-9555-d129df7f3b96-gb8nx
  namespace: openshift-migration
  resourceVersion: "82329"
  selfLink: /apis/velero.io/v1/namespaces/openshift-migration/restores/e13a1b60-c927-11e9-9555-d129df7f3b96-gb8nx
  uid: 26983ec0-c928-11e9-825a-06fa9fb68c88
spec:
  backupName: e13a1b60-c927-11e9-9555-d129df7f3b96-sz24f
  excludedNamespaces: null
  excludedResources:
  - nodes
  - events
  - events.events.k8s.io
  - backups.velero.io
  - restores.velero.io
  - resticrepositories.velero.io
  includedNamespaces: null
  includedResources: null
  namespaceMapping: null
  restorePVs: true
status:
  errors: 0
  failureReason: ""
  phase: Completed
  validationErrors: null
  warnings: 15

Common issues and concerns

This section describes common issues and concerns that can cause issues during migration.

Updating deprecated internal images

If your application uses images from the openshift namespace, the required versions of the images must be present on the target cluster.

If an OKD 3 image is deprecated in OKD 4.15, you can manually update the image stream tag by using podman.

Prerequisites

You must have podman installed.
You must be logged in as a user with cluster-admin privileges.
If you are using insecure registries, add your registry host values to the [registries.insecure] section of /etc/container/registries.conf to ensure that podman does not encounter a TLS verification error.
The internal registries must be exposed on the source and target clusters.

Procedure

Ensure that the internal registries are exposed on the OKD 3 and 4 clusters.

The OpenShift image registry is exposed by default on OKD 4.
If you are using insecure registries, add your registry host values to the [registries.insecure] section of /etc/container/registries.conf to ensure that podman does not encounter a TLS verification error.

$ podman login -u $(oc whoami) -p $(oc whoami -t) --tls-verify=false <registry_url>:<port>

$ podman login -u $(oc whoami) -p $(oc whoami -t) --tls-verify=false <registry_url>:<port>

Pull the OKD 3 image by running the following command:

$ podman pull <registry_url>:<port>/openshift/<image>

Scan the OKD 3 image for deprecated namespaces by running the following command:

$ oc get bc --all-namespaces --template='range .items
"BuildConfig:" .metadata.namespace/.metadata.name =>
"\t""ImageStream(FROM):" .spec.strategy.sourceStrategy.from.namespace/.spec.strategy.sourceStrategy.from.name
"\t""ImageStream(TO):" .spec.output.to.namespace/.spec.output.to.name
end'

Tag the OKD 3 image for the OKD 4 registry by running the following command:
```
$ podman tag <registry_url>:<port>/openshift/<image> \ (1)
  <registry_url>:<port>/openshift/<image> (2)
```
1 Specify the registry URL and port for the OKD 3 cluster.

2 Specify the registry URL and port for the OKD 4 cluster.
Push the image to the OKD 4 registry by running the following command:
```
$ podman push <registry_url>:<port>/openshift/<image> (1)
```
1 Specify the OKD 4 cluster.

Verify that the image has a valid image stream by running the following command:

$ oc get imagestream -n openshift | grep <image>

Example output

NAME      IMAGE REPOSITORY                                                      TAGS    UPDATED
my_image  image-registry.openshift-image-registry.svc:5000/openshift/my_image  latest  32 seconds ago

Direct volume migration does not complete

If direct volume migration does not complete, the target cluster might not have the same node-selector annotations as the source cluster.

Migration Toolkit for Containers (MTC) migrates namespaces with all annotations to preserve security context constraints and scheduling requirements. During direct volume migration, MTC creates Rsync transfer pods on the target cluster in the namespaces that were migrated from the source cluster. If a target cluster namespace does not have the same annotations as the source cluster namespace, the Rsync transfer pods cannot be scheduled. The Rsync pods remain in a Pending state.

You can identify and fix this issue by performing the following procedure.

Procedure

Check the status of the MigMigration CR:

$ oc describe migmigration <pod> -n openshift-migration

The output includes the following status message:

Example output

Some or all transfer pods are not running for more than 10 mins on destination cluster

On the source cluster, obtain the details of a migrated namespace:
```
$ oc get namespace <namespace> -o yaml (1)
```
1 Specify the migrated namespace.
On the target cluster, edit the migrated namespace:
```
$ oc edit namespace <namespace>
```

Add the missing openshift.io/node-selector annotations to the migrated namespace as in the following example:

apiVersion: v1
kind: Namespace
metadata:
  annotations:
    openshift.io/node-selector: "region=east"
...

Run the migration plan again.

Error messages and resolutions

This section describes common error messages you might encounter with the Migration Toolkit for Containers (MTC) and how to resolve their underlying causes.

CA certificate error displayed when accessing the MTC console for the first time

If a CA certificate error message is displayed the first time you try to access the MTC console, the likely cause is the use of self-signed CA certificates in one of the clusters.

To resolve this issue, navigate to the oauth-authorization-server URL displayed in the error message and accept the certificate. To resolve this issue permanently, add the certificate to the trust store of your web browser.

If an Unauthorized message is displayed after you have accepted the certificate, navigate to the MTC console and refresh the web page.

OAuth timeout error in the MTC console

If a connection has timed out message is displayed in the MTC console after you have accepted a self-signed certificate, the causes are likely to be the following:

Interrupted network access to the OAuth server
Interrupted network access to the OKD console
Proxy configuration that blocks access to the oauth-authorization-server URL. See MTC console inaccessible because of OAuth timeout error for details.

To determine the cause of the timeout:

Inspect the MTC console web page with a browser web inspector.
Check the Migration UI pod log for errors.

certificate signed by unknown authority error

If you use a self-signed certificate to secure a cluster or a replication repository for the MTC, certificate verification might fail with the following error message: certificate signed by unknown authority.

You can create a custom CA certificate bundle file and upload it in the MTC web console when you add a cluster or a replication repository.

Procedure

Download a CA certificate from a remote endpoint and save it as a CA bundle file:

$ echo -n | openssl s_client -connect <host_FQDN>:<port> \ (1)
  | sed -ne '/-BEGIN certificate-/,/-END certificate-/p' > <ca_bundle.cert> (2)

1	Specify the host FQDN and port of the endpoint, for example, `api.my-cluster.example.com:6443`.
2	Specify the name of the CA bundle file.

Backup storage location errors in the Velero pod log

If a Velero Backup custom resource contains a reference to a backup storage location (BSL) that does not exist, the Velero pod log might display the following error messages:

$ oc logs <Velero_Pod> -n openshift-migration

Example output

level=error msg="Error checking repository for stale locks" error="error getting backup storage location: BackupStorageLocation.velero.io \"ts-dpa-1\" not found" error.file="/remote-source/src/github.com/vmware-tanzu/velero/pkg/restic/repository_manager.go:259"

You can ignore these error messages. A missing BSL cannot cause a migration to fail.

Pod volume backup timeout error in the Velero pod log

If a migration fails because Restic times out, the following error is displayed in the Velero pod log.

level=error msg="Error backing up item" backup=velero/monitoring error="timed out waiting for all PodVolumeBackups to complete" error.file="/go/src/github.com/heptio/velero/pkg/restic/backupper.go:165" error.function="github.com/heptio/velero/pkg/restic.(*backupper).BackupPodVolumes" group=v1

The default value of restic_timeout is one hour. You can increase this parameter for large migrations, keeping in mind that a higher value may delay the return of error messages.

Procedure

In the OKD web console, navigate to Operators → Installed Operators.
Click Migration Toolkit for Containers Operator.
In the MigrationController tab, click migration-controller.
In the YAML tab, update the following parameter value:
```
spec:
  restic_timeout: 1h (1)
```
1 Valid units are h (hours), m (minutes), and s (seconds), for example, 3h30m15s.
Click Save.

Restic verification errors in the MigMigration custom resource

If data verification fails when migrating a persistent volume with the file system data copy method, the following error is displayed in the MigMigration CR.

Example output

status:
  conditions:
  - category: Warn
    durable: true
    lastTransitionTime: 2020-04-16T20:35:16Z
    message: There were verify errors found in 1 Restic volume restores. See restore `<registry-example-migration-rvwcm>`
      for details (1)
    status: "True"
    type: ResticVerifyErrors (2)

1	The error message identifies the `Restore` CR name.
2	`ResticVerifyErrors` is a general error warning type that includes verification errors.

A data verification error does not cause the migration process to fail.

You can check the Restore CR to identify the source of the data verification error.

Procedure

View the Restore CR:

$ oc describe <registry-example-migration-rvwcm> -n openshift-migration

The output identifies the persistent volume with PodVolumeRestore errors.

Example output

status:
  phase: Completed
  podVolumeRestoreErrors:
  - kind: PodVolumeRestore
    name: <registry-example-migration-rvwcm-98t49>
    namespace: openshift-migration
  podVolumeRestoreResticErrors:
  - kind: PodVolumeRestore
    name: <registry-example-migration-rvwcm-98t49>
    namespace: openshift-migration

View the PodVolumeRestore CR:

$ oc describe <migration-example-rvwcm-98t49>

The output identifies the Restic pod that logged the errors.

Example output

  completionTimestamp: 2020-05-01T20:49:12Z
  errors: 1
  resticErrors: 1
  ...
  resticPod: <restic-nr2v5>

View the Restic pod log to locate the errors:
```
$ oc logs -f <restic-nr2v5>
```

Restic permission error when migrating from NFS storage with root_squash enabled

If you are migrating data from NFS storage and root_squash is enabled, Restic maps to nfsnobody and does not have permission to perform the migration. The following error is displayed in the Restic pod log.

Example output

backup=openshift-migration/<backup_id> controller=pod-volume-backup error="fork/exec /usr/bin/restic: permission denied" error.file="/go/src/github.com/vmware-tanzu/velero/pkg/controller/pod_volume_backup_controller.go:280" error.function="github.com/vmware-tanzu/velero/pkg/controller.(*podVolumeBackupController).processBackup" logSource="pkg/controller/pod_volume_backup_controller.go:280" name=<backup_id> namespace=openshift-migration

You can resolve this issue by creating a supplemental group for Restic and adding the group ID to the MigrationController CR manifest.

Procedure

Create a supplemental group for Restic on the NFS storage.
Set the setgid bit on the NFS directories so that group ownership is inherited.
Add the restic_supplemental_groups parameter to the MigrationController CR manifest on the source and target clusters:
```
spec:
  restic_supplemental_groups: <group_id> (1)
```
1 Specify the supplemental group ID.
Wait for the Restic pods to restart so that the changes are applied.

Known issues

This release has the following known issues:

During migration, the Migration Toolkit for Containers (MTC) preserves the following namespace annotations:
- openshift.io/sa.scc.mcs
- openshift.io/sa.scc.supplemental-groups
- openshift.io/sa.scc.uid-range
  
  These annotations preserve the UID range, ensuring that the containers retain their file system permissions on the target cluster. There is a risk that the migrated UIDs could duplicate UIDs within an existing or future namespace on the target cluster. (BZ#1748440)
Most cluster-scoped resources are not yet handled by MTC. If your applications require cluster-scoped resources, you might have to create them manually on the target cluster.
If a migration fails, the migration plan does not retain custom PV settings for quiesced pods. You must manually roll back the migration, delete the migration plan, and create a new migration plan with your PV settings. (BZ#1784899)
If a large migration fails because Restic times out, you can increase the restic_timeout parameter value (default: 1h) in the MigrationController custom resource (CR) manifest.
If you select the data verification option for PVs that are migrated with the file system copy method, performance is significantly slower.
If you are migrating data from NFS storage and root_squash is enabled, Restic maps to nfsnobody. The migration fails and a permission error is displayed in the Restic pod log. (BZ#1873641)

You can resolve this issue by adding supplemental groups for Restic to the MigrationController CR manifest:
```
spec:
...
  restic_supplemental_groups:
  - 5555
  - 6666
```
If you perform direct volume migration with nodes that are in different availability zones or availability sets, the migration might fail because the migrated pods cannot access the PVC. (BZ#1947487)

Rolling back a migration

You can roll back a migration by using the MTC web console or the CLI.

You can also roll back a migration manually.

Rolling back a migration by using the MTC web console

You can roll back a migration by using the Migration Toolkit for Containers (MTC) web console.

The following resources remain in the migrated namespaces for debugging after a failed direct volume migration (DVM):

Config maps (source and destination clusters)
Secret objects (source and destination clusters)
Rsync CRs (source cluster)

These resources do not affect rollback. You can delete them manually.

If you later run the same migration plan successfully, the resources from the failed migration are deleted automatically.

If your application was stopped during a failed migration, you must roll back the migration to prevent data corruption in the persistent volume.

Rollback is not required if the application was not stopped during migration because the original application is still running on the source cluster.

Procedure

In the MTC web console, click Migration plans.
Click the Options menu beside a migration plan and select Rollback under Migration.
Click Rollback and wait for rollback to complete.

In the migration plan details, Rollback succeeded is displayed.
Verify that rollback was successful in the OKD web console of the source cluster:
1. Click Home → Projects.
2. Click the migrated project to view its status.
3. In the Routes section, click Location to verify that the application is functioning, if applicable.
4. Click Workloads → Pods to verify that the pods are running in the migrated namespace.
5. Click Storage → Persistent volumes to verify that the migrated persistent volume is correctly provisioned.

Rolling back a migration from the command line interface

You can roll back a migration by creating a MigMigration custom resource (CR) from the command line interface.

The following resources remain in the migrated namespaces for debugging after a failed direct volume migration (DVM):

Config maps (source and destination clusters)
Secret objects (source and destination clusters)
Rsync CRs (source cluster)

These resources do not affect rollback. You can delete them manually.

If you later run the same migration plan successfully, the resources from the failed migration are deleted automatically.

If your application was stopped during a failed migration, you must roll back the migration to prevent data corruption in the persistent volume.

Rollback is not required if the application was not stopped during migration because the original application is still running on the source cluster.

Procedure

Create a MigMigration CR based on the following example:

$ cat << EOF | oc apply -f -
apiVersion: migration.openshift.io/v1alpha1
kind: MigMigration
metadata:
  labels:
    controller-tools.k8s.io: "1.0"
  name: <migmigration>
  namespace: openshift-migration
spec:
...
  rollback: true
...
  migPlanRef:
    name: <migplan> (1)
    namespace: openshift-migration
EOF

1	Specify the name of the associated `MigPlan` CR.

In the MTC web console, verify that the migrated project resources have been removed from the target cluster.
Verify that the migrated project resources are present in the source cluster and that the application is running.

Rolling back a migration manually

You can roll back a failed migration manually by deleting the stage pods and unquiescing the application.

If you run the same migration plan successfully, the resources from the failed migration are deleted automatically.

The following resources remain in the migrated namespaces after a failed direct volume migration (DVM):

Config maps (source and destination clusters)
Secret objects (source and destination clusters)
Rsync CRs (source cluster)

These resources do not affect rollback. You can delete them manually.

Procedure

Delete the stage pods on all clusters:

$ oc delete $(oc get pods -l migration.openshift.io/is-stage-pod -n <namespace>) (1)

1	Namespaces specified in the `MigPlan` CR.

Unquiesce the application on the source cluster by scaling the replicas to their premigration number:

$ oc scale deployment <deployment> --replicas=<premigration_replicas>

The migration.openshift.io/preQuiesceReplicas annotation in the Deployment CR displays the premigration number of replicas:

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  annotations:
    deployment.kubernetes.io/revision: "1"
    migration.openshift.io/preQuiesceReplicas: "1"

Verify that the application pods are running on the source cluster:
```
$ oc get pod -n <namespace>
```

Additional resources

Deleting Operators from a cluster using the web console

1	Specify the registry URL and port for the OKD 3 cluster.
2	Specify the registry URL and port for the OKD 4 cluster.