A safe migration of an existing app to a new app, while still having the old app available. So if something goes wrong, you haven't lost the old app.
In this guide, I'll be using the app vaultwarden as an example. I chose the name testwarden for the new app install.
I installed the new app with mostly default settings, just changed service type to ClusterIP and setup a new, temporary, ingress.
We need to run the following commands in the host shell. Everything between <> needs to be replaced with the actual value.
First, we need to get the names of the deploys.
k3s kubectl get deploy -n ix-<old-app>
k3s kubectl get deploy -n ix-<new-app>
Example:
root@truenasvm[/mnt/tank/apps]# k3s kubectl get deploy -n ix-vaultwarden
NAME READY UP-TO-DATE AVAILABLE AGE
vaultwarden 1/1 1 1 3h21m
root@truenasvm[/mnt/tank/apps]# k3s kubectl get deploy -n ix-testwarden
NAME READY UP-TO-DATE AVAILABLE AGE
testwarden-vaultwarden-cnpg-main-rw 2/2 2 2 3h12m
testwarden-vaultwarden 1/1 1 1 3h12m
Here we find the names of the deploys we want to scale down. For apps installed with the default name, it will just be that name.
For apps installed with a different name, it will be <app-name>-<default-name>.
So for vaultwarden (the default name), it will be vaultwarden. But for the vaultwarden app that was installed with the name testwarden, it will be testwarden-vaultwarden.
k3s kubectl scale deploy <app-name>-<default-name> -n ix-<app-name> --replicas=0
k3s kubectl scale deploy <app-name> -n ix-<app-name> --replicas=0
k3s kubectl scale deploy testwarden-vaultwarden -n ix-testwarden --replicas=0
k3s kubectl scale deploy vaultwarden -n ix-vaultwarden --replicas=0
You can skip this section if the app in question doesn't have a Postgresql database
If the app uses a Postgresql database, we need to make a backup and restore that backup to the new app's database. To access the database, the app must be running.
Make sure you have pgAdmin installed, as we'll be using it to make a backup and to restore the database. It's a TrueCharts app from the stable train. You can install it with all default settings, and it will work.