Stuck on Provision TLS certificate for internal Tailscal services

I am trying to log into my Synology from other devices on my Tailscale network, but get certificate error and I am stuck.

After activating htttps in the console, I log into my synology and run in root:

“tailscale cert”

i get:

Usage: tailscale cert [flags]
For domain, use “my domain”.

What step am I missing?

tailscale cert

Thanks for you help jonas:

Ok, I did that, and i got:

Wrote public cert to
Wrote private key to

but when I log in to my synology via a web browser it still says not secure.

You now need to setup tailscale serve.

For example, if your NAS Webadmin port is 5000:

tailscale serve / proxy 5000

this will create a https reverse proxy with the tailscale cert to port 5000.

Now visit