Hello and welcome back. In the previous lesson, we walked through the process of starting a VM and restarting a VM. And I explained a little bit of the things that happen during those processes. In this demonstration here, I just want to show you what happens during a VM stop.

So on the screen, I'm looking at the overview page for VM02. We can see that the VM is in the running state. To stop the VM through the portal, I simply click stop at the top here and then I can see I get this warning about my public IP address. What's happening here is Azure's telling me that once this machine is stopped, it's going to go into the deallocated state and when that happens, the dynamic public IP address can go away. And if I cancel out of here, I can show you why this happens.

Back on the overview page, if I click the IP address that's associated with my VM, the public IP address, we can see that the assignment is dynamic. So a dynamic public IP can go away and reset to another value when a machine is stopped and deallocated. Once that machine comes back up, that IP address can change.

Now if I set this IP to static, what'll happen is the VM may be rebooted. Now let's discard this and we'll go back out to our VM02 virtual machine. Now if we go back into the process of stopping it, again, it asks us if we want to reserve it. We'll tell it yes and then we'll stop it.

If we go ahead and click our IP here, we can see that Azure has now set it to static for us. So now, that IP address will persist throughout stops and restarts even though the VM deallocates.

If we bounce back to our VM02, we'll refresh here, we can see that it's deallocating and now that it's in a stopped state, we can see the IP address hasn't changed. If I start him back up, we can see the IP remains the same. So with that, you now know how to stop a VM from the Azure portal and you know a little bit about what happens with the public IP address.

Now one thing I do want to mention is that when a VM stops, there's a process that happens under the covers that you don't see. What happens when you click stop here, you're sending that stop signal to Microsoft Azure. At that point, what Microsoft Azure does is it sends a signal to the guest OS on that virtual machine and it gives that guest OS a chance to shut down. It's usually around 30 seconds or so.

So what it'll do is it'll allow that VM to shut down the OS. Once that OS is shut down, then Azure will come back and actually stop the VM and deallocate it. So that's why when you stop a VM and start it back up, you won't typically see any kind of errors revolving around dirty shutdowns because that's what's happening.

You're telling Azure to shut it down, Azure's going to the OS saying hey we're gonna power you off, go ahead and do your shutdown routine. The OS does the shutdown, Azure then continues through and then does the shutdown, does the stop, and then does the deallocation. So that's kind of the process that occurs when you stop a virtual machine.