No matter the monitorization solution, CPU utilization is important but if you really want to know what is happening with your system, you should look at load average. I will explain below why.

The current CPU utilization does not reflect the actual load of the system because when a host is heavily loaded, its CPU usage doesn't have to be necessary close to or at 100%.
Furthermore, the CPU utilization tends to generate (in monitoring tools) a significant number of false alerts, even if the percentage alert is close to 100%. Explanation follows.

There are many tutorials over the web regarding this problem but unfortunately it is not always the same for everybody.

In my case I have tried all the links below unsuccessfully (for you it might work):

https://support.apple.com/en-us/HT201349
http://www.idownloadblog.com/2014/05/14/how-to-remove-a-phone-number-from-imessage/
http://www.igeeksblog.com/fix-imessage-waiting-for-activation/

also you can try more:
https://duckduckgo.com/?q=imessage+waiting+for+activation&t=osx

How to get the Citrix XenServer version:

[root@XenGz ~]# cat /etc/redhat-release
XenServer release 6.5.0-90233c (xenenterprise)

[root@XenGz ~]# xe-linux-distribution 
os_distro="xenserver"
os_majorver="6"
os_minorver="5"
os_uname="3.10.0+2"
os_name="XenServer release 6.5.0-90233c (xenenterprise)"

How to list the vhd partitions and get the corresponding snapshosts (if any):

Identify the uuid of the disk you want to attach but also the uuid of the target machine.

You can get the uuid disks with xe vdi-list or even with lvscan.
The VM's uuid you can get in many ways. One of them is:

Citrix Xen has a way to migrate the machines from one host to another via xe vm-export and xe vm-import commands but there are situations when this won't work.
For example, if the source disk is in bad shape and there are bad (unreadable) blocks on your vm's disks, the xe vm-export command will be unsuccessful with the following error:

In this example, the VM name is "debian".

With Debian Jessie, they modified a bit the starting process. I won't get into details because it is not the goal of this article.
Below, you have the proper way to enable and start openvpn.

Launchd is designed to start System and Users daemon/agents located in the following places:

~/Library/LaunchAgents - Per-user agents provided by the user
/Library/LaunchAgents - Per-user agents provided by the administrator
/Library/LaunchDaemons - System-wide daemons provided by the administrator
/System/Library/LaunchAgents - Per-user agents provided by Mac OS X
/System/Library/LaunchDaemons - System wide daemons provided by MAC OS X

Prior to OS X 10.10 Yosemite, you were able to start rc.local script via rc..
That is gone and you have to use launchd.

This tutorial assumes you have already your rc.local script in (example) /etc/rc.local and it is executable and properly populated with your desired commands.
So, without writing too much, below is my example of launchd script:

You use finger command in order to check user information. What if it's missing?
The official replacement for the original finger command and it’s part of the gnu coreutils package, it is called pinky and it’s available on all systems that use the gnu coreutils.