50-cloud-init.yaml, optional: true - will the network interface get initialized if it gets online after the boot sequence?

Question

Good evening

Unfortunately, the Man Page: https://netplan.io/reference is not precise in the description for the optional (bool) property.

If one interface has this setting:

ethernets: 
  eth0: 
    optional: true 

and the Interface gets online some time after the boot sequence, does networkd initialize it as soon as it detects the Interface?

I ask how it is designed/meant to be and not how a specific OS Version implements it :-)

Thanks a lot for any help!

Solution

Without the optional: true statement, ethernet network interfaces that are not completely ready can add an additional 2+ minutes to the boot time.

With the optional: true statement, the boot cycle will continue, without delay, and it'll bring up the ethernet network interfaces when they're ready.

Unless you've got a specific ethernet network interface that MUST be completely operational for other services to properly start, go ahead and add this statement to the other ethernet interface stanzas.