Hack and / - Temper Temper
If loving Linux ever became a crime and I were hauled into court, I think the prosecution's argument would go something like this:
Your honor, I need to submit only two pieces of evidence to make my case. First, I present Exhibit A: a stack of Linux Journal magazines of which the defendant is a columnist.
And your second piece of evidence?
Your honor, the defendant's refrigerator is powered by Linux.
(The audience gasps.) Order! I've heard enough! Guilty!
I can't help it. I mean, why wouldn't you power your fridge with Linux if you had the chance? In my case, we recently purchased a new fridge for our house, which meant our spare fridge was headed for the garage where I would use it for beer fermentation. Fridges are well-insulated, and it seemed ideal for the task at hand, but the problem I ran into was that the built-in thermostat for the fridge would go up to only around 45–50°F at its warmest. To ferment ales, I needed to maintain temperatures between 60–72°F.
When most people convert fridges to ferment beer, they purchase a purpose-built device from their local brew shop. Essentially, you plug your fridge in to the device, plug the device in to the wall, and then set the analog thermostat on the device to your desired temperature. A temperature probe goes into your fridge, and when it gets too warm, the fridge is powered on. These devices range from around $70 to more than $100, depending on whether they are analog or digital, and I almost bought one until I realized I could do the same thing with an old Linux laptop, a couple pieces of hardware and a few scripts.
If you are into home automation at all, you are familiar with the X10 suite of home automation gadgets. Essentially, you can connect lamps and appliances to different X10 gadgets and then power them on with a remote control. There's even a remote control that connects to a serial port, so you can control everything from a computer. Linux has a program called bottlerocket that works great with X10 serial port controllers, and I had used one to control my DSL modem for many years, but that's something for another column.
So, I had a laptop and could control the fridge power, but I still needed a thermometer that worked under Linux and was relatively cheap. I discovered a great little USB-powered thermometer made by a company named TEMPer. It's small, cheap (less than $15 shipped), supports temperatures between –40°C and +120°C, and with a little effort, it works under Linux. It turns out many Linux administrators are using these devices to monitor temperatures in their data centers.
Apparently, the older versions of this thermometer showed up as a USB-to-serial interface; however, the newer models, including the one I bought, show up as a USB Human Interface Device when you plug it in:
Apr 16 14:44:33 muriel kernel: [11601.992205] usb 1-1: ↪new low speed USB device using uhci_hcd and address 2 Apr 16 14:44:33 muriel kernel: [11602.182910] usb 1-1: ↪configuration #1 chosen from 1 choice Apr 16 14:44:33 muriel kernel: [11602.188481] usb 1-1: ↪New USB device found, idVendor=1130, idProduct=660c Apr 16 14:44:33 muriel kernel: [11602.188529] usb 1-1: ↪New USB device strings: Mfr=0, Product=2, SerialNumber=0 Apr 16 14:44:33 muriel kernel: [11602.188563] usb 1-1: ↪Product: PCsensor Temper Apr 16 14:44:35 muriel kernel: [11604.090148] usbcore: ↪registered new interface driver hiddev Apr 16 14:44:35 muriel kernel: [11604.119323] input: ↪PCsensor Temper as /class/input/input7 Apr 16 14:44:35 muriel kernel: [11604.140885] input,hidraw0: ↪USB HID v1.10 Keyboard [ PCsensor Temper] ↪on usb-0000:00:07.2-1 Apr 16 14:44:35 muriel kernel: [11604.170151] input: ↪PCsensor Temper as /class/input/input8 Apr 16 14:44:35 muriel kernel: [11604.188677] input,hidraw1: ↪USB HID v1.10 Device [ PCsensor Temper] ↪on usb-0000:00:07.2-1 Apr 16 14:44:35 muriel kernel: [11604.188931] usbcore: ↪registered new interface driver usbhid Apr 16 14:44:35 muriel kernel: [11604.188980] usbhid: ↪v2.6:USB HID core driver
At first I thought I could get the temperature from this thermometer through some /proc or /sys interface, but unfortunately, the thermometer is more proprietary than that. The Linux community is resourceful though, and a quick search turned up a number of guides on how to pull the temperature from Linux (see Resources for the most helpful guide I found). Essentially, you need to install a few custom Perl modules, including a special one created just for this device that depends on Perl 5.10, so you need a relatively new distribution for this to work (I used the latest stable Debian release).
Kyle Rankin is a VP of engineering operations at Final, Inc., the author of a number of books including DevOps Troubleshooting and The Official Ubuntu Server Book, and is a columnist for Linux Journal. Follow him @kylerankin.
Practical Task Scheduling Deployment
July 20, 2016 12:00 pm CDT
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
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With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide