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Articles indexed in June 2014

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• @CodeStock 2012 Review: Leon Gersing ( @Rubybuddha ) - "You"

  "YOU"Speaker: Leon GersingTwitter: @Rubybuddha Site: http://about.me/leongersing I honestly had no idea what I was getting in to when I sat down in to this session. I basically saw the picture of the speaker and knew that it would be a good session. I was completely wrong; it was the BEST SESSION of CodeStock 2012.  In fact it was so good, I texted another coworker attending the conference to get over and listen to Leon. Leon took on the concept of growth in the software development community. He specifically referred David Hansson in his ability to stick to his beliefs when the development community thought that he was crazy for creating Ruby on Rails. If you do not know this story Ruby on Rails is one of the fastest growing web languages today. In addition, he also touched on the flip side of this argument in that we must be open to others ideas and not discard them so quickly because we all come from differing perspectives and can add value to a project/team/community. This session left me with two very profound concepts/quotes: “In order to learn you must do it badly in front of a crowed and fail.” - @Rubybuddha I can look back on my career so far and say that he is correct; I think I have learned the most after failing, especially when I achieved this failure in front of other. “Experts must be able to fail.” - @Rubybuddha I think we can all learn from our own mistakes but we can also learn from others. When respected experts fail it is a great learning opportunity for the entire team as well as the person who failed. When expert admit mistakes and how they worked through them can be great learning tools for other developers so that they know how to avoid specific scenarios and if they do become stuck in the same issue they will know how to properly work their way out of them.

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• CodeStock 2012 Review: Michael Eaton( @mjeaton ) - 3 Simple Things for Increased Productivity

  3 Simple Things for Increased ProductivitySpeaker: Michael EatonTwitter: @mjeatonBlog: http://mjeaton.net/blog This was the first time I had seen Michael Eaton speak but have hear a lot of really good things about his speaking abilities. Needless to say I was really looking forward to his session. He basically addressed the topic of distractions and how they can decrease or increase your productivity as a developer. He makes the case that in order to become more productive you must block/limit all distractions. For example, he covered his top distractions as a developer. Top Distractions Social Media(Twitter, Reddit, Facebook) Wiki sites Phone Email Video Games Coworkers, Friends, Family Michael stated that he uses various types of music to help him block out these distractions in order for him to get into his coding zone. While he states that music works for him, he also notes that he knows of others that cannot really work with music. I have to say I am in the latter group because I require a quiet environment in order to work. A few session attendees also recommended listening to really loud white noise or music in another language other than your own. This allows for less focus to be placed on words being sung compared to the rhythmic beats being played. I have to say that I have not tried these suggestions yet but will in the near future. However, distractions can be very beneficial to productivity in that they give your mind a chance to relax and not think about the issues at hand. He spoke highly of taking vacations, and setting boundaries at work so that develops prevent the problem of burnout. One way he suggested that developer’s combat distractions is to use the Pomodoro technique. In his example he selects one task to do for 20 minutes and he can only do that task during that time. He ignores all other distractions until this task or time limit is complete. After it is completed he allows himself to relax and distract himself for another 5- 10 minutes before his next Pomodoro. This allows him to stay completely focused on a task and when the time is up he can then focus on other things.

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• CodeStock 2012 Review: Eric Landes( @ericlandes ) - Automated Tests in to automated Builds! How to put the right type of automated tests in to the right automated builds.

  Automated Tests in to automated Builds! How to put the right type of automated tests in to the right automated builds.Speaker: Eric LandesTwitter: @ericlandesBlog: http://ericlandes.com/ This was one of the first sessions I attended during CodeStock 2012. Eric’s talk focused mostly on unit testing, and that the lack of proper unit testing can be compared to stealing from an employer. His point was that if you’re not doing proper unit testing then all of the time wasted on fixing issues that could have been detected with unit tests is like stealing money from employer. He makes the assumption that that time spent on fixing these issues could have been better spent developing new features that drive the business. To a point I can agree with Eric’s argument regarding unit testing and stealing from a company’s perspective. I can see how he relates resources being shifted from new development to bug fixes as stealing based on the fact that the resources used to fix bugs are directly taken from other projects. He also states that Boring/Redundant and Build/Test tasks should be automated because it reduces the changes of errors and frees up developer to do what they do best, DEVELOP! When he refers to testing, he breaks testing down in to four distinct types. Unit Test Acceptance Test (This also includes Integration Tests) Performance Test UI Test With this he also recommends that developers should not go buck wild striving for 100% code coverage because some test my not provide a great return on investment. In his experience he recommends that 70% test coverage was a very acceptable rate.

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• Application Logging needs work

  Application Logging Application logging is the act of logging events that occur within an application much like how a court report documents what happens in court case. Application logs can be useful for several reasons, but the most common use for logs is to recreate steps to find the root cause of applications errors. Other uses can include the detection of Fraud, verification of user activity, or provide audits on user/data interactions. “Logs can contain different kinds of data. The selection of the data used is normally affected by the motivation leading to the logging. “ (OWASP, 2009) OWASP also stats that logging include applicable debugging information like the event date time, responsible process, and a description of the event. “There are many reasons why a logging system is a necessary part of delivering a distributed application. One of the most important is the ability to track exactly how many users are using the application during different time periods.” (Hatton, 2000) Hatton also states that application logging helps system designers determine whether parts of an application aren't being used as designed. He implies that low usage can be used to identify if users like or do not like aspects of a system based on user usage of the application. This enables application designers to extract why users don't like aspects of an application so that changes can be made to increase its usefulness and effectiveness. “Logging memory usage can also assist you in tuning up the internals of your application. If you're experiencing a randomly occurring problem, being able to match activities performed with the memory status at the time may enable you to discover the cause of the problem. It also gives you a good indication of the health of the distributed server machine at the time any activity is performed. “ (Hatton, 2000) Commonly Logged Application Events (Defined by OWASP) Access of Data Creation of Data Modification of Data in any form Administrative Functions  Configuration Changes Debugging Information(Application Events)  Authorization Attempts  Data Deletion Network Communication  Authentication Events  Errors/Exceptions Application Error Logging The functionality associated with application error logging is actually the combination of proper error handling and applications logging.  If we look back at Figure 4 and Figure 5, these code examples allow developers to handle various types of errors that occur within the life cycle of an application’s execution. Application logging can be applied within the Catch section of the TryCatch statement allowing for the errors to be logged when they occur. By placing the logging within the Catch section specific error details can be accessed that help identify the source of the error, the path to the error, what caused the error and definition of the error that occurred. This can then be logged and reviewed at a later date in order recreate the error that was received based data found in the application log. By allowing applications to log errors developers IT staff can use them to recreate errors that are encountered by end-users or other dependent systems.

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• Why do VMs need to be "stack machines" or "register machines" etc.?

  - by Prog

  (This is an extremely newbie-ish question). I've been studying a little about Virtual Machines. Turns out a lot of them are designed very similarly to physical or theoretical computers. I read that the JVM for example, is a 'stack machine'. What that means (and correct me if I'm wrong) is that it stores all of it's 'temporary memory' on a stack, and makes operations on this stack for all of it's opcodes. For example, the source code 2 + 3 will be translated to bytecode similar to: push 2 push 3 add My question is this: JVMs are probably written using C/C++ and such. If so, why doesn't the JVM execute the following C code: 2 + 3..? I mean, why does it need a stack, or in other VMs 'registers' - like in a physical computer? The underlying physical CPU takes care of all of this. Why don't VM writers simply execute the interpreted bytecode with 'usual' instructions in the language the VM is programmed with? Why do VMs need to emulate hardware, when the actual hardware already does this for us? Again, very newbie-ish questions. Thanks for your help

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• Very simple OOP question

  - by Mosty Mostacho

  I was creating and discussing a class diagram with a partner of mine. To simplify things, I've modify the real domain we're working on and made up the following diagram: Basically, a company works on constructions that are quite different one from each other but are still constructions. Note I've added one field for each class but there should be many more. Now, I thought this was the way to go but my partner told me that if in the future new construction classes appear we would have to modify the Company class, which is correct. So the new proposed class diagram would be this: Now I've been wondering: Should the fact that in no place of the application will there be mixed lists of planes and bridges affect the design in any way? When we have to list only planes for a company, how are we supposed to distinguish them from the other elements in the list without checking for their class names? Related to the previous question, is it correct to assume that this type of diagram should be high-level and this is something it shouldn't matter at this stage but rather be thought and decided at implementation time? Any comment will be appreciated.

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• Override a static library's global function

  - by Jason Madux

  Not sure if this question belongs here or on SO, but posting here for now :) I'm trying to override a global function defined in "StaticLib" for my iOS application but the compiler keeps giving me the duplicate symbol error. Relevant code: #import "MyApplication.h" #import "StaticLib.h" NSData* getAllData() { NSLog(@"myGetAllData"); return nil; } @implementation MyApplication ... @end I've looked into Apple's runtime library but that all seems to be class-oriented. Any suggestions or is it just not possible to override global functions from static libraries?

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• Time passage arithmetic explanation

  - by Cyber Axe

  I ported this from http://www.effectgames.com/effect/article.psp.html/joe/Old_School_Color_Cycling_with_HTML5 some time ago. However i'm now wanting to modify it for the purpose of changing it from floating point to fixed point maths for enhanced efficiency (for those who are going to talk about premature optimization and what not, i want to have my entire engine in fixed point both as a learning process for me and so i can port code more easily to systems in the future that dont have native floating points such as arm cpus) My initial conversion to fixed points just resulted in the cycling stuck on either the first or last frame of cycling. Plus it would be nice to understand better how it works so i can add more options and so forth in the future, my maths however sucks and the comments are limited so i don't really know how the maths work for determining the frame it shoud use (cycleAmount) I was also a beginner when i ported it as i had no idea between floating points and integers and what not. So in summary my question is, can anyone give an explination of the arithmatic used for determining the cycleAmount (which determings the "frame" of the cycle) This is the working floating point maths version of the code: public final void cycle(Colour[] sourceColours, double timeNow, double speedAdjust) { // Cycle all animated colour ranges in palette based on timestamp. sourceColours = sourceColours.clone(); int cycleSize; double cycleRate; double cycleAmount; Cycle cycle; for (int i = 0, len = cycles.length; i < len; ++i) { cycle = cycles[i]; cycleSize = (cycle.HIGH - cycle.LOW) + 1; cycleRate = cycle.RATE / (int) (CYCLE_SPEED / speedAdjust); cycleAmount = 0; if (cycle.REVERSE < 3) { // Standard Cycle cycleAmount = DFLOAT_MOD((timeNow / (1000 / cycleRate)), cycleSize); if (cycle.REVERSE < 1) { cycleAmount = cycleSize - cycleAmount; // If below 1 make sure its not reversed. } } else if (cycle.REVERSE == 3) { // Ping-Pong cycleAmount = DFLOAT_MOD((timeNow / (1000 / cycleRate)), cycleSize << 1); if (cycleAmount >= cycleSize) { cycleAmount = (cycleSize * 2) - cycleAmount; } } else if (cycle.REVERSE < 6) { // Sine Wave cycleAmount = DFLOAT_MOD((timeNow / (1000 / cycleRate)), cycleSize); cycleAmount = Math.sin((cycleAmount * 3.1415926 * 2) / cycleSize) + 1; if (cycle.REVERSE == 4) { cycleAmount *= (cycleSize / 4); } else if (cycle.REVERSE == 5) { cycleAmount *= (cycleSize >> 1); } } if (cycle.REVERSE == 2) { reverseColours(sourceColours, cycle); } if (USE_BLEND_SHIFT) { blendShiftColours(sourceColours, cycle, cycleAmount); } else { shiftColours(sourceColours, cycle, cycleAmount); } if (cycle.REVERSE == 2) { reverseColours(sourceColours, cycle); } } colours = sourceColours; } // This utility function allows for variable precision floating point modulus. private double DFLOAT_MOD(final double d, final double b) { return (Math.floor(d * PRECISION) % Math.floor(b * PRECISION)) / PRECISION; }

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• Strict C++ guidelines [on hold]

  - by Banex

  Some time ago I ran across an answer here on Programmers that linked a Wikipedia page about some strict guidelines for C++. The only thing I remember is that it didn't allow exceptions and was in general very strict, and that it was used in many workplaces where most C++ features are not considered useful, or are not available (embedded systems, etc). I'd like to know the name of those guidelines, as I searched the whole internet without finding it.

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• In what order does the Asset-Pipeline in Ruby on Rails load JavaScript Files? [on hold]

  - by psycatham

  So, when I decided to remove the tags <script></script> and benefit from the asset-pipeline instead, complications took place. I am working with Google Maps' API V3, and to benefit from their functions and objects that their code provides, you have load the link first <script src="https://maps.googleapis.com/maps/api/js?v=3.exp&libraries=places"></script> Basically, If I put this line before their code, and put their code in script tags, things work out pretty perfecty, but when I use javascript_include_tag instead of script tag in html and copy my code to the file I pointed at -Like This - <script src="https://maps.googleapis.com/maps/api/js?v=3.exp&libraries=places"></script> <%=javascript_include_tag "map_new_marker_drag"%> , the asset-pipeline seems to load That file before loading the link of Google Maps API, thus I get the error : - Uncaught ReferenceError : google is undefined I tried putting the link in javascript_include_tag too -Like this- <%=javascript_include_tag "https://maps.googleapis.com/maps/api/js?v=3.exp&libraries=places" %> <%=javascript_include_tag "map_new_marker_drag"%> , and it generated this <script src="https://maps.googleapis.com/maps/api/js?v=3.exp&amp;libraries=places"></script> <script src="https://maps.gstatic.com/cat_js/intl/en_us/mapfiles/api-3/17/2/%7Bmain,places%7D.js" type="text/javascript"></script> <script src="/assets/map_new_marker_drag.js?body=1"></script> and the same error Uncaught ReferenceError : google is undefined. Do I have to put it in another order? what am I missing about the asset-pipeline mechanisms? What should I do to make the link load before the code so to benefit from their objects and get rid of the error? PS : I tried using jquery functions and so , but I seem not to make it happen. If you still think this is a proper solution, please provide me some code I can use this is the jquery function I used jQuery(function($) { // Asynchronously Load the map API var script = document.createElement('script'); script.src = "http://maps.googleapis.com/maps/api/js?sensor=false&callback=initialize"; document.body.appendChild(script); var scriptTwo = document.createElement('script'); scriptTwo.src = "https://maps.googleapis.com/maps/api/js?v=3.exp&libraries=places"; document.body.appendChild(scripTwo); });

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• Is the test, which touches the filenames under directory, a kind of unittest? [on hold]

  - by Chen OT

  I was told that unittest is fast and the tests which touches DB, across network, and touches FileSystem are not unittest. In one of my testcases, its input are the file names (amount about 300~400) under a specific folder. Although these input are part of file system, the execution time of this test is very fast. Should I moved this test, which is fast but touches file system, to higher level test?

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• Extract all related class type aliasing and enum into one file or not

  - by Chen OT

  I have many models in my project, and some other classes just need the class declaration and pointer type aliasing. It does not need to know the class definition, so I don't want to include the model header file. I extract all the model's declaration into one file to let every classes reference one file. model_forward.h class Cat; typedef std::shared_ptr<Cat> CatPointerType; typedef std::shared_ptr<const Cat> CatConstPointerType; class Dog; typedef std::shared_ptr<Dog> DogPointerType; typedef std::shared_ptr<const Dog> DogConstPointerType; class Fish; typedef std::shared_ptr<Fish> FishPointerType; typedef std::shared_ptr<const Fish> FishConstPointerType; enum CatType{RED_CAT, YELLOW_CAT, GREEN_CAT, PURPLE_CAT} enum DogType{HATE_CAT_DOG, HUSKY, GOLDEN_RETRIEVER} enum FishType{SHARK, OCTOPUS, SALMON} Is it acceptable practice? Should I make every unit, which needs a class declaration, depends on one file? Does it cause high coupling? Or I should put these pointer type aliasing and enum definition inside the class back? cat.h class Cat { typedef std::shared_ptr<Cat> PointerType; typedef std::shared_ptr<const Cat> ConstPointerType; enum Type{RED_CAT, YELLOW_CAT, GREEN_CAT, PURPLE_CAT} ... }; dog.h class Dog { typedef std::shared_ptr<Dog> PointerType; typedef std::shared_ptr<const Dog> ConstPointerType; enum Type{HATE_CAT_DOG, HUSKY, GOLDEN_RETRIEVER} ... } fish.h class Fish { ... }; Any suggestion will be helpful.

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• Finding most Important Node(s) in a Directed Graph

  - by Srikar Appal

  I have a large (˜ 20 million nodes) directed Graph with in-edges & out-edges. I want to figure out which parts of of the graph deserve the most attention. Often most of the graph is boring, or at least it is already well understood. The way I am defining "attention" is by the concept of "connectedness" i.e. How can i find the most connected node(s) in the graph? In what follows, One can assume that nodes by themselves have no score, the edges have no weight & they are either connected or not. This website suggest some pretty complicated procedures like n-dimensional space, Eigen Vectors, graph centrality concepts, pageRank etc. Is this problem that complex? Can I not do a simple Breadth-First Traversal of the entire graph where at each node I figure out a way to find the number of in-edges. The node with most in-edges is the most important node in the graph. Am I missing something here?

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• Design Application to "Actively" Invite Users (pretend they have privileges)

  - by user3086451

  I am designing an application where users message one another privately, and may send messages to any Entity in the database (an Entity may not have a user account yet, it is a professional database). I am not sure how to best design the database and the API to allow messaging unregistered users. The application should remain secure, and data only accessed by those with correct permissions. Messages sent to persons without user accounts serve as an invitation. The invited person should be able to view the message, act on it, and complete the user registration upon receiving an InviteMessage. In simple terms, I have: User misc user fields (email, pw, dateJoined) Entity (large professional dataset): personalDetails... user->User (may be null) UserMessage: sender->User recipient->User dateCreated messageContent, other fields..... InviteMessage: sender->User recipient->Entity expiringUrl inviteeEmail inviteePhone I plan to alert the user when selecting a recipient that is not registered yet, and inform that he may send the message as an invitation by providing email, phone where we can send the invitation. Invitations will have a unique, one-time-use URL, e.g. uuid.uuid4(). When accessed, the invitee will see the InviteMessage and details about completing his/her registration profile. When registration is complete, InviteMessage details to a new instance of UserMessage (to not lose their data), and assign it to the newly created User. The ability to interact with and invite persons who do not yet have accounts is a key feature of the application, and it seems better to separate the invitation from the private, app messages (easier to keep functionality separate, better if data model changes). Is this a reasonable, good design? If not, what would you suggest? Do you have any improvements? Am I correct to choose to create a separate endpoint for creating invitations via the API?

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• What is a practical way to debug Rails?

  - by Joshua Fox

  I get the impression that in practice, debuggers are rarely used for Rails applications. (Likewise for other Ruby apps, as well as Python.) We can compare this to the usual practice for Java or VisualStudio programmers--they use an interactive debugger in a graphical IDE. How do people debug Rails applications in practice? I am aware of the variety of debuggers, so no need to mention those, but do serious Rails programmers work without them? If so, why do you choose to do it this way? It seems to me that console printing has its limits when debugging complex logic.

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• Cannot execute binary file

  - by user291727

  I am new to Ubuntu and I'm trying to install Popcorn Time. I downloaded 32 bit version and tried to install it but that's where the problem started showing. I duble clicked the executable file and well, nothing happened. It's a official download from their web-site but it doesn't work. Maybe I'm doing something wrong.....Anyway, I found out that you can insatll it from a script, but people keep talking in ubuntu terms and I don't understand it, so I have a few questions: 1.How to make a script? (witch I'm suppose to run in terminal using bash comand), 2.Is it normal that i cannot run the installer, and if that is an installer or just files for the program. 3.If it is an installer, how do I make it work? 4.What does " Cannot execute binary file" mean? Thank you in advance, hope I'm not asking too many questions(please understand that I'm new to ubuntu) and sorry about my English. xD

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• '6' key stuck when outside the graphical interface

  - by Felipe Jacob

  A strange thing has been happening since I installed Ubuntu. Whenever I'm not on the graphical interface, that is, if I do ctrl+alt+f2, or while the system is shutting down, or when I try to reset my password accessing root on security mode, the '6' key seems to be stuck. This doesn't affect my day-to-day usage at all, but whenever I change from the graphical console, I can't do anything because it keeps pressing '666666...'. Does anyone know why that might be happening? My keyboard is a Logitech G710+, and hasn't shown any other possible compatibility issues.

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• XRDP crashes when using xfce desktop

  - by user291721

  I've been struggling with this for a few days. Currently using Ubuntu 14.04. I started out trying to use VNC and could connect but only received a black and white checkered screen when connecting using tightvnc from my windows machine. Seems that applications seem to have issues interpreting the gnome graphics. I then tried XRDP and received the same issue but was able to find enough information to get by this issue. After creating a .xsession file and setting the desktop to spawn an xfce4-session I was able to connect and the desktop displays, at least for a few seconds. After a couple seconds rdp crashes and I'm unable to connect again until I restart the xrdp service. Any help would be appreciated. Thanks

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• Is it possible to hide Launcher for certain apps?

  - by Przemek

  As 14.04LTS has been released I thought I'd try to make larger switch to Ubuntu - especially considering most of the apps I use at work are at last available in Linux versions (with the major exception being Rhino3d v5 - hope that it will be possible to launch it with Wine somehow). But as I use my PC for 3D design I need every damn inch of screen space. And this is where Launcher becomes a pain. While in general I like it (as well as the rest of Unity) when I do office work (emails, docs etc) it has turned out to be a major pain with 3D apps and tablet. I'd like to set launcher to hide when certain apps are maximized. Is it possible? If not is it possible to set it as intellihide/stay in the background globally, so it won't be visible when any app is maximized? Autohide is (sadly) not a good solution - the way Ubuntu handles revealing the hidden bar is tricky to work with when you use a graphic tablet (but to be honest I have gripes with it even when using a mouse). I need the bar to disappear or stay in the background so it won't take screen space - 3D apps have way too much menus that eat valuable screen space already.

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• Bless doesn't fix white boot screen boot delay for single-boot Xubuntu 14.04 on Macbook 4,1

  - by elephant

  I still have a 30-second delay on the white boot-up screen before Xubuntu loads after trying various combinations of bless --device as recommended here: https://help.ubuntu.com/community/MactelSupportTeam/AppleIntelInstallation#Avoid_long_EFI_wait_before_GRUB I wonder if anyone has experienced this before, or can point me to some good steps for troubleshooting this issue? I have cycled my macbook dozens of times, it would be great to be able to boot quicker. I am single-booting Xubuntu 14.04 (no Mac OSX partitions or any other OS, just a GRUB partition at sda1, a main partition at sda2, and a swap at the end of the drive). Suggestions very appreciated.

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• the correct way to deal with gtk_events_pending and gtk_main_iteration

  - by abd alsalam

  I have program that send files and i want to make a progress bar for it, but that progress bar just updated after the transferring complete,so i putted a gtk_events_pending() and gtk_main_iteration() functions in the sending loop to go back to the gtk main loop to update the progress bar but also it seems to not work here is a EDIT: the send function is in a separated thread snippet from my code float Percent = 0.0 ; float Interval = 0.0 ; the sending function gint SendTheFile ( ) { char FileBlockBuffer[512]; bzero(FileBlockBuffer, 512); int FileBlockSize ; FILE * FilePointer ; int filesize = 0 ; FilePointer = fopen(LocalFileName , "r"); struct stat st; stat(LocalFileName, &st); filesize = st.st_size; Interval = (512 / (float)filesize) ; while((FileBlockSize = fread(FileBlockBuffer,sizeof(char),512,FilePointer))>0) { send(SocketDiscriptor , FileBlockBuffer , FileBlockSize,0); bzero(FileBlockBuffer, 512); Percent = Percent + Interval ; if (Percent > 1.0)Percent = 0.0; while(gtk_events_pending() ) { gtk_main_iteration(); } } update progress bar function gint UpdateProgressBar(gpointer data) { gtk_progress_bar_set_fraction(GTK_PROGRESS_BAR(data),Percent); } updating progress bar in the main function g_timeout_add(50,(GSourceFunc)UpdateProgressBar,SendFileProgressBar);

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• ec2 instance won't boot!

  - by TheToolBox

  So I had a server lose connection while updating to 14.04LTS. Foolishly, it ended up getting rebooted, and now I'm here. I disconnected the volume and mounted it on another system, chrooted it, and updated the kernel. Still no dice. Any idea what the problem could be? Thanks in advance! The instance log is below: ******************* BLKFRONT for device/vbd/2049 ********** backend at /local/domain/0/backend/vbd/3005/2049 Failed to read /local/domain/0/backend/vbd/3005/2049/feature-barrier. Failed to read /local/domain/0/backend/vbd/3005/2049/feature-flush-cache. 16777216 sectors of 512 bytes ************************** [H[J Booting 'Ubuntu 14.04 LTS, memtest86+' root (hd0) Filesystem type is ext2fs, using whole disk kernel /boot/memtest86+.bin ============= Init TPM Front ================ Tpmfront:Error Unable to read device/vtpm/0/backend-id during tpmfront initialization! error = ENOENT Tpmfront:Info Shutting down tpmfront xc: error: panic: xc_dom_core.c:621: xc_dom_find_loader: no loader found: Invalid kernel xc_dom_parse_image returned -1 close(3) Error 9: Unknown boot failure Press any key to continue...

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• Unable to record from USB sound card line-in connector

  - by tete

  I've been googling and struggling with this for a while but haven't been able to make this work. I bought a USB sound card (Encore ENMAB 8-CM) to record from its line-in connector. I'm not sure which input to pick in Audicity, but I'me sure I've tested them all. These are all the available inputs I have in Audacity. But there's no sound being recorded at all. I've already checked the device is working, so I really don't know if I'm doing something wrong. Any help will be very appreciated. Cheers.

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• No more internet connection after update in 14.04 with Intel Dual Band Wireless AC 7260

  - by luis

  My Dell XPS 15 (haswell) was working fine until I stupidly accepted recently to apply Ubuntu updates. Since then, my wifi does not work (it shows "device not managed" when clicking wifi icon in toolbar). Even USB to Ethernet adapter does not seem to work. Bluetooth at least "sees" other bluetooth devices around... See below output from dmesg (dmesg |grep iwl) : [ 886.462459] iwlwifi 0000:06:00.0: irq 51 for MSI/MSI-X [ 886.462561] iwlwifi 0000:06:00.0: Direct firmware load failed with error -2 [ 886.462562] iwlwifi 0000:06:00.0: Falling back to user helper [ 886.463284] iwlwifi 0000:06:00.0: loaded firmware version 22.1.7.0 op_mode iwlmvm [ 886.475345] iwlwifi 0000:06:00.0: Detected Intel(R) Dual Band Wireless AC 7260, REV=0x144 [ 886.475433] iwlwifi 0000:06:00.0: L1 Enabled; Disabling L0S [ 886.475684] iwlwifi 0000:06:00.0: L1 Enabled; Disabling L0S [ 886.689214] ieee80211 phy0: Selected rate control algorithm 'iwl-mvm-rs' Below the output from modinfo iwlwifi: filename: /lib/modules/3.13.0-29- generic/kernel/drivers/net/wireless/iwlwifi/iwlwifi.ko license: GPL author: Copyright(c) 2003-2013 Intel Corporation <[email protected]> version: in-tree: description: Intel(R) Wireless WiFi driver for Linux firmware: iwlwifi-100-5.ucode firmware: iwlwifi-1000-5.ucode firmware: iwlwifi-135-6.ucode firmware: iwlwifi-105-6.ucode firmware: iwlwifi-2030-6.ucode firmware: iwlwifi-2000-6.ucode firmware: iwlwifi-5150-2.ucode firmware: iwlwifi-5000-5.ucode firmware: iwlwifi-6000g2b-6.ucode firmware: iwlwifi-6000g2a-5.ucode firmware: iwlwifi-6050-5.ucode firmware: iwlwifi-6000-4.ucode firmware: iwlwifi-3160-7.ucode firmware: iwlwifi-7260-7.ucode srcversion: 1E6912E109D5A43B310FB34 alias: pci:v00008086d0000095Asv*sd00005490bc*sc*i* (a pack of lines of kind "alias: pci:xxxxx...." that I guess are not helpful) alias: pci:v00008086d0000095Bsv*sd00005290bc*sc*i* depends: cfg80211 intree: Y vermagic: 3.13.0-29-generic SMP mod_unload modversions signer: Magrathea: Glacier signing key sig_key: 66:02:CB:36:F1:31:3B:EA:01:C4:BD:A9:65:67:CF:A7:23:C9:70:D8 sig_hashalgo: sha512 parm: swcrypto:using crypto in software (default 0 [hardware]) (int) parm: 11n_disable:disable 11n functionality, bitmap: 1: full, 2: disable agg TX, 4: disable agg RX, 8 enable agg TX (uint) parm: amsdu_size_8K:enable 8K amsdu size (default 0) (int) parm: fw_restart:restart firmware in case of error (default true) (bool) parm: antenna_coupling:specify antenna coupling in dB (defualt: 0 dB) (int) parm: wd_disable:Disable stuck queue watchdog timer 0=system default, 1=disable, 2=enable (default: 0) (int) parm: nvm_file:NVM file name (charp) parm: bt_coex_active:enable wifi/bt co-exist (default: enable) (bool) parm: led_mode:0=system default, 1=On(RF On)/Off(RF Off), 2=blinking, 3=Off (default: 0) (int) parm: power_save:enable WiFi power management (default: disable) (bool) parm: power_level:default power save level (range from 1 - 5, default: 1) (int) I downloaded the latest versions of iwlwifi firmware from git (git clone git://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git; copy iwlwifi-3160-9.ucode iwlwifi-7260-9.ucode iwlwifi-7265-9.ucode to /lib/firmware and reboot) but as you can imagine it did not help. Update #1: Downloaded from http://wireless.kernel.org/en/users/Drivers/iwlwifi?action=AttachFile&do=get&target=iwlwifi-7260-ucode-22.15.8.0.tgz and copied the file into /lib/firmware. After reloading it with modprobe, it seems to be OK: [ 14.761283] iwlwifi 0000:06:00.0: enabling device (0000 -> 0002) [ 14.761472] iwlwifi 0000:06:00.0: irq 51 for MSI/MSI-X [ 14.772478] iwlwifi 0000:06:00.0: loaded firmware version 22.15.8.0 op_mode iwlmvm [ 14.800274] iwlwifi 0000:06:00.0: Detected Intel(R) Dual Band Wireless AC 7260, REV=0x144 [ 14.800349] iwlwifi 0000:06:00.0: L1 Enabled; Disabling L0S [ 14.800657] iwlwifi 0000:06:00.0: L1 Enabled; Disabling L0S [ 15.007048] ieee80211 phy0: Selected rate control algorithm 'iwl-mvm-rs' However, clicking in wifi in the toolbar still shows "device not managed". Any clues? Many thanks! Luis

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• Ubuntu 14.04 upgrade succeeded partially - I would like to use a different mirror; how can I do that?

  - by user290648

  When I wanted to upgrade from Ubuntu 13.10 to 14.04 the update manager told me that there was an unresolvable problem with calculating the upgrade. In order to see more details I performed the following on the command line: apt-get update apt-get upgrade apt-get dist-upgrade apt-get install update-manager-core do-release-upgrade Now do-release-upgrade tells me that no newer version is available but the "about" box in the main menu tells me I am still on 13.10. I think the latter is right, as for instance in the "system settings" there is no way to select local menus, which is present in 14.04 (I tried with a DVD, and there it is). Maybe the problem is related to the fact that "apt-get update" cannot get two resources called "saucy/InRelease" and "saucy/main/binary-i386/Packages" from the mirror (mirror.informatik.uni-mannheim.de; 404 not found). I would like to use a different mirror; how can I do that? Any help appreciated, thanks in advance.

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