Our smallest network has just three systems permanently attached to a 100/1000 router. There is one additional port available to temporarily plug in a laptop. The largest systems are both Dells, one running Windows 7 and one running CentOS 6.7. The Windows 7 system supports three flavors of Linux as virtual machines. The CentOS system is often used for data file import from USB-attached devices such as cell phones, charging batteries in the USB-attached devices, and for access to external email accounts.
The CentOS system was in power save mode when I plugged in a Samsung cell phone for charging and extraction of several photo files. I then moved to the Windows 7 system to do some "paper work" on a web site that is known to require the use of IE for browser access. While on the Windows 7 system I did a quick email check and responded to one of our contacts at a remote site. He was having "difficulty" with file from an external site downloaded on his Windows 7 system. I took the opportunity in my email reply to comment on the great safety and stability of Linux systems.
After about two hours I returned to the CentOS 6.7 system to check on the charging status and move the photo files. Yellow lights were showing on both computer and monitor. The system display, and the optical mouse would not return to normal operation as they usually do with a quick push on the front power button. The power button light did turn green and I was able to log in via ssh from a Cygwin shell on the Windows 7 system. It took two reboots executed remotely to bring back full display and mouse functionality.
I believe that this was the first time anyone has plugged in a USB device into the CentOS 6.7 system while it is in power save mode.We now have a warning tag hanging over the USB ports on the system. Is there some characteristic of CentOS systems that we should have known about that could have caused this problem? Does Yahoo web mail have an easy way to retract my gloating email?