Write Concurrent Apps in C with libmill ™ WATCH: ISSUE OVERVIEW V AUGUST 2016 | ISSUE 268 http://www.linuxjournal.com Since 1994: The Original Magazine of the Linux Community CREATE YOUR OWN TINY INTERNET Technology Make Qubes Travel Tips +A New Project Even More Secure for Linux at 25 LJ268-Aug2016.indd 1 7/20/16 10:32 AM NEW! Beyond Cron, Machine Part II: Learning Deploying with Python a Modern Practical books Author: Scheduling Reuven M. Lerner Alternative Sponsor: for the most technical Intel Author: Mike Diehl people on the planet. Sponsor: Skybot Linux on Hybrid Cloud Power: Security with Why Open z Systems Architecture Author: GEEK GUIDES Matters Petros Koutoupis Author: Sponsor: Ted Schmidt IBM Sponsor: IBM LinuxONE: Ceph: the Ubuntu Open-Source Monster SDS Author: Author: John S. Tonello Ted Schmidt Sponsor: Sponsor: IBM SUSE Download books for free with a Linux on SSH: a simple one-time registration. Power Modern Author: Lock for http://geekguide.linuxjournal.com Ted Schmidt Your Server? Sponsor: Author: HelpSystems Federico Kereki Sponsor: Fox Technologies LJ268-Aug2016.indd 2 7/20/16 10:32 AM NEW! Beyond Cron, Machine Part II: Learning Deploying with Python a Modern Practical books Author: Scheduling Reuven M. Lerner Alternative Sponsor: for the most technical Intel Author: Mike Diehl people on the planet. Sponsor: Skybot Linux on Hybrid Cloud Power: Security with Why Open z Systems Architecture Author: GEEK GUIDES Matters Petros Koutoupis Author: Sponsor: Ted Schmidt IBM Sponsor: IBM LinuxONE: Ceph: the Ubuntu Open-Source Monster SDS Author: Author: John S. Tonello Ted Schmidt Sponsor: Sponsor: IBM SUSE Download books for free with a Linux on SSH: a simple one-time registration. Power Modern Author: Lock for http://geekguide.linuxjournal.com Ted Schmidt Your Server? Sponsor: Author: HelpSystems Federico Kereki Sponsor: Fox Technologies LJ268-Aug2016.indd 3 7/20/16 10:32 AM AUGUST 2016 CONTENTS ISSUE 268 Cover Image: © Can Stock Photo Inc. / crstrbrt FEATURES 80 The Tiny 112 Coroutines and Internet Project, Channels in Part III C Using libmill Learn Linux by doing: the Love Golang’s goroutines and conclusion to the building an channels? Learn how you can internet-in-a-box project explore them in C using libmill. John S. Tonello Amit Saha 4 | August 2016 | http://www.linuxjournal.com LJ268-Aug2016.indd 4 7/20/16 10:32 AM CONTENTS COLUMNS 38 Reuven M. Lerner’s At the Forge Transitioning to Python 3 46 Dave Taylor’s 30 Work the Shell Finishing Up the Content Spinner 52 Kyle Rankin’s Hack and / Secure Desktops with Qubes: Extra Protection 60 Shawn Powers’ The Open-Source Classroom 60 Sometimes My Office Goes with Me 134 Doc Searls’ EOF A New Project for Linux at 25 IN EVERY ISSUE 8 Current_Issue.tar.gz 10 Letters 80 18 UPFRONT ON THE COVER 36 Editors’ Choice >YP[L*VUJ\YYLU[(WWZPU*^P[OSPITPSSW *YLH[L@V\Y6^U;PU`0U[LYUL[W 72 New Products 4HRL8\ILZ,]LU4VYL:LJ\YLW ;LJOUVSVN`;YH]LS;PWZW 143 Advertisers Index (5L^7YVQLJ[MVY3PU\_H[W LINUX JOURNAL (ISSN 1075-3583) is published monthly by Belltown Media, Inc., PO Box 980985, Houston, TX 77098 USA. Subscription rate is $29.50/year. Subscriptions start with the next issue. 5 | August 2016 | http://www.linuxjournal.com LJ268-Aug2016.indd 5 7/20/16 10:32 AM Executive Editor Jill Franklin [email protected] Senior Editor Doc Searls [email protected] Associate Editor Shawn Powers [email protected] Art Director Garrick Antikajian [email protected] Products Editor James Gray [email protected] Editor Emeritus Don Marti [email protected] Technical Editor Michael Baxter [email protected] Senior Columnist Reuven Lerner [email protected] Security Editor Mick Bauer [email protected] Hack Editor Kyle Rankin lj@greenfly.net Virtual Editor Bill Childers [email protected] Contributing Editors )BRAHIM (ADDAD s 2OBERT ,OVE s :ACK "ROWN s $AVE 0HILLIPS s -ARCO &IORETTI s ,UDOVIC -ARCOTTE 0AUL "ARRY s 0AUL -C+ENNEY s $AVE 4AYLOR s $IRK %LMENDORF s *USTIN 2YAN s !DAM -ONSEN President Carlie Fairchild [email protected] Publisher Mark Irgang [email protected] Associate Publisher John Grogan [email protected] Director of Digital Experience Katherine Druckman [email protected] Accountant Candy Beauchamp [email protected] Linux Journal is published by, and is a registered trade name of, Belltown Media, Inc. 0/ "OX (OUSTON 48 53! Editorial Advisory Panel Nick Baronian Kalyana Krishna Chadalavada "RIAN #ONNER s +EIR $AVIS -ICHAEL %AGER s 6ICTOR 'REGORIO $AVID ! ,ANE s 3TEVE -ARQUEZ $AVE -C!LLISTER s 4HOMAS 1UINLAN #HRIS $ 3TARK s 0ATRICK 3WARTZ Advertising % -!),: [email protected] 52,: www.linuxjournal.com/advertising 0(/.% EXT Subscriptions % -!),: [email protected] 52,: www.linuxjournal.com/subscribe -!), 0/ "OX (OUSTON 48 53! LINUX IS A REGISTERED TRADEMARK OF ,INUS 4ORVALDS LJ268-Aug2016.indd 6 7/20/16 10:32 AM Manage data expansion You with SUSE Enterprise cannot Storage. SUSE Enterprise Storage, the leading open source storage solution, is highly keep up scalable and resilient, enabling high-end functionality at a fraction of with data the cost. explosion. suse.com/storage Data LJ268-Aug2016.indd 7 7/20/16 10:32 AM Current_Issue.tar.gz Linux: Just Do It! SHAWN I recently had a conversation with a person in the POWERS TECH WORLD WHO DOES A LOT OF HIRING (E STARTED OUR CONVERSATION WITH A PRETTY OPEN ENDED REQUEST Shawn Powers is the Associate Editor for “Shawn, talk to me about Linux and how it matters Linux Journal. He’s TO PEOPLE LOOKING FOR A JOBv ) ASSUMED HE WAS also the Gadget Guy asking me why people should or shouldn’t add Linux for LinuxJournal.com, and he has an expertise to their résumés. Or, perhaps he was trying interesting collection TO GET ME TO EXPLAIN WHY A ,INUX PROFESSIONAL IS A of vintage Garfield value even in an environment largely containing coffee mugs. Don’t let his silly hairdo -ICROSOFT PRODUCTS ) WAS ABSOLUTELY INCORRECT 4HE fool you, he’s a VALUE OF ,INUX ALREADY WAS ASSUMED (E WAS ASKING pretty ordinary guy how people should go about gaining training and and can be reached via email at experience! Let me say that again, the value of [email protected]. Linux was already assumed. It’s like we’re living in Or, swing by the THE FUTURE /N THAT NOTE LETS LEARN ABOUT ,INUX #linuxjournal IRC channel on 2EUVEN - ,ERNER STARTS OFF THIS ISSUE WITH A Freenode.net. HOW TO ON MIGRATING FROM 0YTHON TO 0YTHON 4HE TRANSITION WAS SUCH THAT CODE DOESNT AUTOMATICALLY WORK IN VERSION IF IT WORKED IN V VERSION 4HATS NOT TO SAY ITS NOT WORTH MOVING TO JUST THAT IT REQUIRES WORK 2EUVEN GIVES TIPS ON VIDEO: working through that process incrementally. Shawn .EXT $AVE 4AYLOR FINISHES HIS SERIES ON hSPINNINGv Powers runs text, creating automated, personalized messages. It’s through A FASCINATING LOOK AT HOW COMPUTERS ARE BEING USED the latest issue. TO DO THE SORTS OF THINGS THAT USED TO REQUIRE A HUMAN touch. Plus, it’s just really awesome to see in action! 8 | August 2016 | http://www.linuxjournal.com LJ268-Aug2016.indd 8 7/20/16 10:32 AM Current_Issue.tar.gz Let me say that again, the value of Linux was already assumed. It’s like we’re living in the future! #ONTINUING HIS SERIES ON 1UBES +YLE 2ANKIN IS BACK THIS MONTH EXPLAINING HOW TO SECURE THE SECURITY FOCUSED DISTRIBUTION EVEN FURTHER &IGURING OUT THE ADVANCED FEATURES OF 1UBES IS JUST ONE MORE WAY TO MAKE YOUR SECURE ENVIRONMENT CUSTOMIZED FOR YOUR SECURITY NEEDS -Y COLUMN THIS ISSUE IS MORE INFORMATIONAL THAN EDUCATIONAL ) OFTEN AM asked about what I use on a daily basis, and I’m traveling this month, so ) FIGURED IT WAS THE PERFECT TIME TO TALK ABOUT HOW ) WORK WHEN TRAVELING )M PROBABLY DRASTICALLY DIFFERENT FROM ANYONE ELSE BUT PERHAPS ONE OR TWO THINGS ) DO MIGHT BE USEFUL FOR MY FELLOW NERDY TRAVELERS *OHN 3 4ONELLO PROVIDES PART OF HIS h4INY )NTERNET 0ROJECTv WHERE HE TEACHES HOW TO CREATE YOUR OWN DIVERSE NETWORK INFRASTRUCTURE USING VIRTUALIZATION AND ELBOW GREASE 4HIS MONTH YOULL LEARN HOW TO GET THOSE installed systems going, so you can do whatever experimentation or LEARNING YOU DESIRE )F YOUVE BEEN FOLLOWING ALONG WITH THIS PROJECT YOU won’t want to miss this conclusion. Finally, Amit Saha delves deep into development with a look AT COROUTINES AND CHANNELS IN THE # LANGUAGE )F YOU ARE WRITING concurrent applications in C, you’ll want to check out the libmill library, and Amit walks through its usage. Just like every month, we have extensive looks at new products, REVIEWS OF EXISTING TECHNOLOGY TIPS AND TRICKS 0LUS WE HAVE A LOOK AT THE IMPLICATIONS OF ,INUX AND OPEN SOURCE IN OUR SOCIETY WITH $OC 3EARLS %/& 7HETHER YOU ARE JUST LEARNING ,INUX TO MAKE YOUR RÏSUMÏ SPARKLE OR are trying to learn even better ways to utilize Linux in your environment, THIS ISSUE IS BOUND TO PLEASE 7E HOPE YOU ENJOY IT AS MUCH AS WEVE enjoyed putting it together!Q RETURN TO CONTENTS 9 | August 2016 | http://www.linuxjournal.com LJ268-Aug2016.indd 9 7/20/16 10:32 AM LETTERS[ LETTERS ] PREVIOUS NEXT V V Current_Issue.tar.gz UpFront Doc Searls’ June 2016 Column ) AGREE WITH MOST OF $OCS COMMENTS ) STARTED WITH )"- ALMOST YEARS AGO AND ) HAVE SEEN THE COMPUTER INFRASTRUCTURE EXPAND AND CONTRACT IN AN ENDLESS CYCLE OF CENTRALIZED AND DISTRIBUTED EXTREMES !S AN EARLY USER OF #OMPU3ERVE ) CAN RECALL THE FRUSTRATION WITH BOTH THE EXPENSE AND LIMITATIONS OF ITS IDEA OF hEMAILv AND hNETWORKINGv !LTHOUGH ) CAN SEE SOME POSITIVE ATTRIBUTES OF THE SOCIAL MEDIA ENGINES to me, they don’t really have a product other than trapping me into their MAZE OF ADVERTISING %VEN THE INTERNET IS BECOMING MORE AND MORE FRUSTRATING ) WOULD MUCH RATHER SUBSCRIBE TO MY FAVORITE SITES THAN DEAL WITH THE BARRAGE OF unwanted ads.