Feature: Post-deployment scripts for upgrades

[scott1138]

We use the flexvol driver to allow for SMB connections from our AKS clusters. After an upgrade we have to go through and re-install it on each node. This means several pods are unable to start. I don't want to risk touch the servers during the process, but if the process itself could re-install VM extensions that were previously installed or execute a designated script as it completes each node before it enables it for scheduling that would save on downtime.

[ellieayla]

How are you installing the flexvol driver on each node?

[scott1138]

@alanjcastonguay using the Linux custom script extension that uses the below url for the install script which it downloads and then executes.

https://raw.githubusercontent.com/Azure/kubernetes-volume-drivers/master/flexvolume/smb/deployment/install-smb-flexvol-ubuntu.sh

[jluk]

Similar discussion to #1532 however a daemonset could be utilized to customize nodes through each replacement.