Migrating from version 3 to 4 overview | Migrating from version 3 to 4

Differences between OKD 3 and 4
Planning network considerations
Installing MTC
Upgrading MTC
Reviewing premigration checklists
Migrating applications
Advanced migration options
Troubleshooting migrations
Rolling back a migration
Uninstalling MTC and deleting resources

OKD 4 clusters are different from OKD 3 clusters. OKD 4 clusters contain new technologies and functionality that result in a cluster that is self-managing, flexible, and automated. To learn more about migrating from OKD 3 to 4 see About migrating from OpenShift Container Platform 3 to 4.

Differences between OKD 3 and 4

Before migrating from OKD 3 to 4, you can check differences between OKD 3 and 4. Review the following information:

Architecture
Installation and update
Storage, network, logging, security, and monitoring considerations

Planning network considerations

Before migrating from OKD 3 to 4, review the differences between OKD 3 and 4 for information about the following areas:

DNS considerations
- Isolating the DNS domain of the target cluster from the clients.
- Setting up the target cluster to accept the source DNS domain.

You can migrate stateful application workloads from OKD 3 to 4 at the granularity of a namespace. To learn more about MTC see Understanding MTC.

If you are migrating from OKD 3, see About migrating from OKD 3 to 4 and Installing the legacy Migration Toolkit for Containers Operator on OKD 3.

Installing MTC

Review the following tasks to install the MTC:

Upgrading MTC

You upgrade the Migration Toolkit for Containers (MTC) on OKD 4.15 by using OLM. You upgrade MTC on OKD 3 by reinstalling the legacy Migration Toolkit for Containers Operator.

Reviewing premigration checklists

Before you migrate your application workloads with the Migration Toolkit for Containers (MTC), review the premigration checklists.

Migrating applications

You can migrate your applications by using the MTC web console or the command line.

Advanced migration options

You can automate your migrations and modify MTC custom resources to improve the performance of large-scale migrations by using the following options:

Troubleshooting migrations

You can perform the following troubleshooting tasks:

Rolling back a migration

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

Uninstalling MTC and deleting resources

You can uninstall the MTC and delete its resources to clean up the cluster.

Migration from OpenShift Container Platform 3 to 4 overview