We will be covering some essential command line tools. I thought mentioning the top three command line tools would be a good idea. There are a lot of different directions we can go from here but let's focus on the Xen commands that I think are crucial for measuring and monitoring performance.
Once again the purpose of this Appendix section is not to give you detailed information and examples for every flag that a utility such as
virsh may have. We will only explore some of the important ones and leave the rest for you to exercise. There is no better way of learning than trying it all yourself. The purpose of this book is to get you excited and started.
Let's try all of the arguments one by one and see what they mean.
Without any arguments we get all the information of the VMs running in this VM Server. As you can see in the preceding screenshot, we have a 64 bit PVM Oracle 11g Database Virtual Appliance, 64 bit HVM Windows 2003 Server, a 32bit HVM Windows XP machine, and a 64bit PVM Oracle ELU2 VM.
We also see the information such as total memory on the VM Server, amount of memory used, free memory, and the number of CPUs.
So xentop provides you with real-time information of your running Oracle VM Server. Here you can see and take the right action like moving VMs to another box or allocating more resources to a VM.
If xentop is a mighty utility, xm is the core utility within Xen. It is actually the command control suite with a huge amount of arguments which we shall learn about, soon. However, as mentioned earlier, we will not explore everything about those arguments lest we add another hundred or so pages to the book.
xm-help command shows you why we cannot discuss every little argument here. However, I will explain on my blog the utilities associated with Xen and other versions of Xen such as Oracle VM, and so on.
We will run a few arguments against the xm utility powerhouse.
Xm dmesg: Read the Xen Daemon Message Buffer and if needed clean it. Here we type in the basic syntax for the
xm dmesg with an optional argument
-c, which clears the contents of the ring buffer while it displays it, as shown in the following screenshot:
Attaching and detaching new virtual NICs: Show the visible NICs before attaching a virtual NIC to a domain or a VM. Here, we give an extra virtual NIC to a VM by issuing
xm network-attach 14 command. It then attaches the new virtual NIC to that VM:
Always remember that a lot of actions, if your Oracle IntraCloud VM farm is configured properly, can be carried out from the VM Manager console.