I’m beginner in rancher
Why do you want to delete the old Rancher container after an upgrade?
If you are running Rancher in Single node mode. You don’t have to delete it container but we don’t want that container to be started by accident after the upgrade. I normally recommend keeping for a couple of days just in case you need to roll back.
It is important to note that single node mode is no longer supported in Rancher v2.6+ for production installs and as it’s really only designed for POC or lab environments.
We do have a migration path which can be found at Migrating a Rancher Single Node to a HA Installation