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  • How to create a shared folder using command line on a server

    - by sadmicrowave
    After following the tutorial here I ran into a problem. Here is what I did. On my server I installed nfs-kernel-server and edited the /etc/exports file to include the folder I want to share: /var *(rw,sync) On my client machine I edited my fstab file to include share: //128.251.xxx.xxx/var/ ~/uslonsweb003 nfs #username=[username],password=[password], 0 0 Entered command: sudo mount -a which gives this error: mount.nfs: remote share not in 'host:dir' format Where did I go wrong with this setup? Also if there is a better way (using command line) to setup a folder share on an Ubuntu 10.10 server that will be accessed by other linux and windows machines please let me know. UPDATE: The mapped drive is now not letting me create,edit,delete files or folders (readonly access) my configuration is as follows: client fstab file: 128.251.xxx.xxx:/var /home/coreyf/uslonsweb003 nfs rw,hard,intr, 0 0 server exports file: /var *(rw,no_root_squash,sync,no_subtree_check) UPDATE 2: Using Allans solution my drive mounted correctly however after putting rw,intr as my additional parameters I cannot create, edit and delete folders/files.

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  • API design and versioning using EJB

    - by broschb
    I have an API that is EJB based (i.e. there are remote interfaces defined) that most of the clients use. As the client base grows there are issues with updates to the API and forcing clients to have to update to the latest version and interface definition. I would like to possibly look at having a couple versions of the API deployed at a time (i.e. have multiple EAR files deployed with different versions of the API) to support not forcing the clients to update as frequently. I am not concerned about the actual deployment of this, but instead am looking for thoughts and experiences that others have on using EJB's as an API client. How do you support updating versions, are clients required to update? Does anyone run multiple versions in a production environment? Are there pro's cons? Any other experiences or thoughts on this approach, and having an EJB centric API?

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  • Ops Center Update 2 is available!

    - by Owen Allen
    Oracle Enterprise Manager Ops Center Release 1, Update 2 (12.1.2.0.0) is available. This release includes support for Oracle Solaris 11.1 and Oracle Linux 6.3, the ability to attach a network multiple times to an LDom guest using the same vswitch, support for HMP 2.2.3, improved options for adding users from remote directory servers, and a few other useful features. A list of new features is in What's New. You can view the documentation online, or you can download a zip file of the library from the Overview tab. If you're running Ops Center in connected mode, the updates are delivered to the UI. If you are in disconnected mode or have not yet installed Ops Center, you can go to the Ops Center download page to get the latest release. Before installing or upgrading to Ops Center 12c Update 2, review the Release Notes for things to watch out for, then see the upgrade instructions in the Administration Guide.

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  • All video players display black screen.

    - by Dennis
    I'm working in 10.04 Lucid. All my video players (Movie Player and VLC) and the preview windows in editors (OpenShot and Pitivi) will only display a black screen when playing a video. The sound is fine and the videos work fine on other computers. I have tried multiple formats from varying sources .MOV taken from old ffmpeg projects, .AVI straight from a camera, .MP4 using h.264 from OpenShot on another system, .OGV from a gtk-recordmydesktop session on this very computer. I even get a pure black screen in the viewer when starting a remote session in VNC. This box has a GeForce 8400 GS using the Nvidia drivers in case it may be a card problem or setting.

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  • Notifications for Expiring DBSNMP Passwords

    - by Courtney Llamas
    Most user accounts these days have a password profile on them that automatically expires the password after a set number of days.   Depending on your company’s security requirements, this may be as little as 30 days or as long as 365 days, although typically it falls between 60-90 days. For a normal user, this can cause a small interruption in your day as you have to go get your password reset by an admin. When this happens to privileged accounts, such as the DBSNMP account that is responsible for monitoring database availability, it can cause bigger problems. In Oracle Enterprise Manager 12c you may notice the error message “ORA-28002: the password will expire within 5 days” when you connect to a target, or worse you may get “ORA-28001: the password has expired". If you wait too long, your monitoring will fail because the password is locked out. Wouldn’t it be nice if we could get an alert 10 days before our DBSNMP password expired? Thanks to Oracle Enterprise Manager 12c Metric Extensions (ME), you can! See the Oracle Enterprise Manager Cloud Control Administrator’s Guide for more information on Metric Extensions. To create a metric extension, select Enterprise / Monitoring / Metric Extensions, and then click on Create. On the General Properties screen select either Cluster Database or Database Instance, depending on which target you need to monitor.  If you have both RAC and Single instance you may need to create one for each. In this example we will create a Cluster Database metric.  Enter a Name for the ME and a Display Name. Then select SQL for the Adapter.  Adjust the Collection Schedule as desired, for this example we will collect this metric every 1 day. Notice for metric collected every day, we can determine the exact time we want to collect. On the Adapter page, enter the query that you wish to execute.  In this example we will use the query below that specifically checks for the DBSNMP user that is expiring within 10 days. Of course, you can adjust this query to alert for any user that can cause an outage such as an application account or service account such as RMAN. select username, account_status, trunc(expiry_date-sysdate) days_to_expirefrom dba_userswhere username = 'DBSNMP'and expiry_date is not null; The next step is to create the columns to store the data returned from the query.  Click Add and add a column for each of the fields in the same order that data is returned.  The table below will help you complete the column additions. Name Display Name Column Type Value Type Metric Category Unit Username User Name Key String Security AccountStatus Account Status Data String Security DaysToExpire Days Until Expiration Data Number Security Days When creating the DaysToExpire column, you can add a default threshold here for Warning and Critical (say < 10 and 5).  When all columns have been added, click Next. On the Credentials page, you can choose to use the default monitoring credentials or specify new credentials.  We will use the default credentials established for our target (dbsnmp). The next step is to test your Metric Extension.  Click on Add to select a target for testing, then click Select. Now click the button Run Test to execute the test against the selected target(s). We can see in the example below that the Metric Extension has executed and returned a value of 68 days to expire. Click Next to proceed. Review the metric extension in the final screen and click Finish. The metric will be created in Editable status.  Select the metric, click Actions and select Deployable Draft. You can do this once more to move to Published. Finally, we want to apply this metric to a target. When managing many targets, it’s best to add your metric to a template, for details on adding a Metric Extension to a template see the Administrator’s Guide. For this example, we will deploy this to a target directly. Select Actions / Deploy to Targets. Click Add and select the target you wish to deploy to and click Submit.  Once deployment is complete, we can go to the target and view the Metric & Collection Settings to see the new metric and its thresholds.   After some time, you will find the metric has collected and the days to expiration for DBSNMP user can be seen in the All Metrics view.   For metrics collected once per day, you may have to wait up to 24 hours to see the metric and current severity. In the example below, the current severity is Clear (green check) as it is not scheduled to expire within 10 days. To test the notification, we can edit the thresholds for the new metric so they trigger an alert.  Our password expires in 139 days, so we’ll change our Warning to 140 and leave Critical at 5, in our example we also changed the collection time to every 5 minutes.  At the next collection, you’ll find that the current severity changes to a Warning and any related Incident Rules would be triggered to create an Incident or Notification as desired. Now that you get a notification that your DBSNMP passwords is about to expire, you can use OEM Command Line Interface (EM CLI) verb update_db_password to change it at both the database target and the OEM target in one step.  The caveat is you must know the existing password to use the update_db_password command.  To learn more about EM CLI, see the Oracle Enterprise Manager Command Line Interface Guide.  Below is an example of changing the password with the update_db_password verb.  $ ./emcli update_db_password -target_name=emrep -target_type=oracle_database -user_name=dbsnmp -change_at_target=yes -change_all_references=yes Enter value for old_password :Enter value for new_password :Enter value for retype_new_password :Successfully submitted a job to change the password in Enterprise Manager and on the target database: "emrep"Execute "emcli get_jobs -job_id=FA66C1C4D663297FE0437656F20ACC84" to check the status of the job.Search for job name "CHANGE_PWD_JOB_FA66C1C4D662297FE0437656F20ACC84" on the Jobs home page to check job execution details. The subsequent job created will typically run quickly enough that a blackout is not needed, however if you submit a script with many targets to change, your job may run slower so adding a blackout to the script is recommended. $ ./emcli get_jobs -job_id=FA66C1C4D663297FE0437656F20ACC84 Name Type Job ID Execution ID Scheduled Completed TZ Offset Status Status ID Owner Target Type Target Name CHANGE_PWD_JOB_FA66C1C4D662297FE0437656F20ACC84 ChangePassword FA66C1C4D663297FE0437656F20ACC84 FA66C1C4D665297FE0437656F20ACC84 2014-05-28 09:39:12 2014-05-28 09:39:18 GMT-07:00 Succeeded 5 SYSMAN oracle_database emrep After implementing the above Metric Extension and using the EM CLI update_db_password verb, you will be able to stay on top of your DBSNMP password changes without experiencing an unplanned monitoring outage.  

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  • Code review process when using GIT as a repository?

    - by Sid
    What is the best process for code review when using GIT? Current process: We have a GIT server with a master branch to which everyone commits Devs work off the local master mirror or a local feature branch Devs commit to server's master branch Devs request code review on last commit Problem: Any bug in code review are already in master by the time it's caught. Worse, usually someone has burnt a few hours trying to figure out what happened... So, we would like To do code review BEFORE delivery into the 'master'. Have a process that works with a global team (no over the shoulder reviews!) something that doesn't require an individual dev to be at his desk/machine to be powered up so someone else can remote in (remove human dependency, devs go home at different timezones) We use TortoiseGIT for a visual representation of a list of files changed, diff'ing files etc. Some of us drop into a GIT shell when the GUI isn't enough, but ideally we'd like the workflow to be simple and GUI based (I want the tool to lift any burden, not my devs).

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  • Finding Telecommuting Opportunities as a Recent College Graduate

    - by stanigator
    Reading the answers to hiring practices of remote vs. local employees and freelance programming sites, I would like to add this question to the mix. I am a recent college graduate from an electrical engineering background with 2 years worth of work terms in programming (C, C++, VBA, Matlab, etc.) while I was still in school. While I am interested in learning other software tools (such as Python, Ruby on Rails, Javascript, etc.), I want to use the tools I have now in a telecommuting role while I grow my toolset. Despite having 2 years of work experience (and I've lost track of when I have started programming), my status as a recent college graduate may be an obstacle of my credibility to compete for telecommuting (or in fact any) programming opportunities. I don't know how I can go about finding telecommute programming opportunities for someone with my situation. Overall, many of previous places I've worked at liked my work. What are your suggestions? Thanks in advance!

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  • How do I share different files in a git repo with different people?

    - by David Faux
    In a single directory with a Git root folder, I have a bunch of files. I am working on one of those files, X.py, with my friend Alice. The other files I am working on with other people. I want Alice (and everyone else) to have access to X.py. I want Alice to only have access to X.py though. How can I achieve this with Git? Is there a way I can split a directory into two repos? That sounds rather cumbersome. Maybe I could add a remote repo that Alice can access containing X.py?

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  • Simulating Smartphones on PC with Unity

    - by Cengiz Frostclaw
    I want to make a game that depends on the phone orientation (changing shoot direction with tilt), however I need to test this on PC. So is there any tool I can use to simulate the orientation of the phone with mouse or keyboard of my PC? Something like joysticks on the screen. Thanks for any help! Edit : Thanks to @jhocking for his suggestion of Unity Remote. I, however still can accept a solution with using only PC, since I'm afraid of shortening my phone's battery life, for some reason.

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  • How to prevent code from leaking outside work?

    - by AeroCross
    I'm working on an institution that has a really strong sense of "possession" - each line of software we write should be only ours. Ironically, I'm the only programmer (ATM), but we're planning in hiring others. Since my bosses wouldn't count the new programmers as people they can trust, they have an issue with the copies of the source code. We use Git, so they would have a entire copy of each of the projects they work on, when they clone the repository. We can restrict access to them to a single key with Gitolite and bind that to their PC's, but they can copy those keys to another computer and they would have the repository access in another PC. Also (and the most obvious method) they could just upload the files somewhere else, add another remote, or just copy the files to an USB drive. Is there any (perhaps clever) way to prevent events like these?

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  • SQL Peer-to-Peer Dynamic Structured Data Processing Collaboration

    Unstructured and XML semi-structured data is now used more than structured data. But fixed structured data still keeps businesses running day in and day out, which requires consistent predictable highly principled processing for correct results. For this reason, it would be very useful to have a general purpose SQL peer-to-peer collaboration capability that can utilize highly principled hierarchical data processing and its flexible and advanced structured processing to support dynamically structured data and its dynamic structured processing. This flexible dynamic structured processing can change the structure of the data as necessary for the required processing while preserving the relational and hierarchical data principles. This processing will perform freely across remote unrelated peer locations anytime and transparently process unpredictable and unknown structured data and data type changes automatically for immediate processing using automatic metadata maintenance.

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  • Working on a virtual machine as a developer

    - by Johnny000
    In the company I'm currently working in, they decided that each developer will move to a VM desktop (Citrix/WinServer2012) an develop/test from there with restricted/no rights to install new software. The Server we will be working on are in a remote Datacenter. So i.e. if for some reason or another the internet brake down, we can't work till the connection is up again. As a developer I don't want to use windows as OS for my working/development environment as there is no need because we don't develop OS specific software. What good points could I raise in an argumentation against moving to the VMs beside the loss/restriction of freedom and the loss of connection to the internet?

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  • Discussion of a Distributed Data Storage implementation

    - by fegol
    I want to implement a distributed data storage using a client/server architecture. Each data item will be stored persistently in disk in one of several remote servers. The client uses a library to update and query the data, shielding the client from its actual location. This should allow a client to associate keys (String) to values(byte[]), much as a Map does. The system must ensure that the amount of data stored in each server is approximately the same. The set of servers is known beforehand by other servers and clients. Both the client and the server will be written in Java, using sockets, threads, and files. I open this topic with the objective of discussing the best way to implement this idea, assuming simplicity, what are the issues of this implementation, performance measurements and discussion of the limitations.

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  • JavaDay Taipei 2014 Trip Report

    - by reza_rahman
    JavaDay Taipei 2014 was held at the Taipei International Convention Center on August 1st. Organized by Oracle University, it is one of the largest Java developer events in Taiwan. This was another successful year for JavaDay Taipei with a fully sold out venue packed with youthful, energetic developers (this was my second time at the event and I have already been invited to speak again next year!). In addition to Oracle speakers like me, Steve Chin and Naveen Asrani, the event also featured a bevy of local speakers including Taipei Java community leaders. Topics included Java SE, Java EE, JavaFX, cloud and Big Data. It was my pleasure and privilege to present one of the opening keynotes for the event. I presented my session on Java EE titled "JavaEE.Next(): Java EE 7, 8, and Beyond". I covered the changes in Java EE 7 as well as what's coming in Java EE 8. I demoed the Cargo Tracker Java EE BluePrints. I also briefly talked about Adopt-a-JSR for Java EE 8. The slides for the keynote are below (click here to download and view the actual PDF): It appears your Web browser is not configured to display PDF files. No worries, just click here to download the PDF file. In the afternoon I did my JavaScript + Java EE 7 talk titled "Using JavaScript/HTML5 Rich Clients with Java EE 7". This talk is basically about aligning EE 7 with the emerging JavaScript ecosystem (specifically AngularJS). The talk was completely packed. The slide deck for the talk is here: JavaScript/HTML5 Rich Clients Using Java EE 7 from Reza Rahman The demo application code is posted on GitHub. The code should be a helpful resource if this development model is something that interests you. Do let me know if you need help with it but the instructions should be fairly self-explanatory. I am delivering this material at JavaOne 2014 as a two-hour tutorial. This should give me a little more bandwidth to dig a little deeper, especially on the JavaScript end. I finished off Java Day Taipei with my talk titled "Using NoSQL with ~JPA, EclipseLink and Java EE" (this was the last session of the conference). The talk covers an interesting gap that there is surprisingly little material on out there. The talk has three parts -- a birds-eye view of the NoSQL landscape, how to use NoSQL via a JPA centric facade using EclipseLink NoSQL, Hibernate OGM, DataNucleus, Kundera, Easy-Cassandra, etc and how to use NoSQL native APIs in Java EE via CDI. The slides for the talk are here: Using NoSQL with ~JPA, EclipseLink and Java EE from Reza Rahman The JPA based demo is available here, while the CDI based demo is available here. Both demos use MongoDB as the data store. Do let me know if you need help getting the demos up and running. After the event the Oracle University folks hosted a reception in the evening which was very well attended by organizers, speakers and local Java community leaders. I am extremely saddened by the fact that this otherwise excellent trip was scarred by terrible tragedy. After the conference I joined a few folks for a hike on the Maokong Mountain on Saturday. The group included friends in the Taiwanese Java community including Ian and Robbie Cheng. Without warning, fatal tragedy struck on a remote part of the trail. Despite best efforts by us, the excellent Taiwanese Emergency Rescue Team and World class Taiwanese physicians we were unable to save our friend Robbie Cheng's life. Robbie was just thirty-four years old and is survived by his younger brother, mother and father. Being the father of a young child myself, I can only imagine the deep sorrow that this senseless loss unleashes. Robbie was a key member of the Taiwanese Java community and a Java Evangelist at Sun at one point. Ironically the only picture I was able to take of the trail was mere moments before tragedy. I thought I should place him in that picture in profoundly respectful memoriam: Perhaps there is some solace in the fact that there is something inherently honorable in living a bright life, dying young and meeting one's end on a beautiful remote mountain trail few venture to behold let alone attempt to ascend in a long and tired lifetime. Perhaps I'd even say it's a fate I would not entirely regret facing if it were my own. With that thought in mind it seems appropriate to me to quote some lyrics from the song "Runes to My Memory" by legendary Swedish heavy metal band Amon Amarth idealizing a fallen Viking warrior cut down in his prime: "Here I lie on wet sand I will not make it home I clench my sword in my hand Say farewell to those I love When I am dead Lay me in a mound Place my weapons by my side For the journey to Hall up high When I am dead Lay me in a mound Raise a stone for all to see Runes carved to my memory" I submit my deepest condolences to Robbie's family and hope my next trip to Taiwan ends in a less somber note.

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  • My ubuntuone is broken, what is the problem?

    - by user6962
    I am on 10.10 and u1sdtool seems to be completely broken. I reinstalled it, no change. I can add my PC to the account, but it is added twice(!) every time I tried. So I have my netbook and two times my PC in the account. The netbook with 10.04 has no problems. Below is the error msg I get when attempting to startup Ubuntu One on the command line. desktop:~$ u1sdtool --status Oops, an error ocurred: Traceback (most recent call last): Failure: dbus.exceptions.DBusException: org.freedesktop.DBus.Error.NoReply: Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken. desktop:~$ Starting it from the Me Menu has the same effect, the HDD will get really busy for a minute and then nothing happens, the client will not start. Nothing in the syslog or anywhere.

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  • parallel_for_each from amp.h – part 1

    - by Daniel Moth
    This posts assumes that you've read my other C++ AMP posts on index<N> and extent<N>, as well as about the restrict modifier. It also assumes you are familiar with C++ lambdas (if not, follow my links to C++ documentation). Basic structure and parameters Now we are ready for part 1 of the description of the new overload for the concurrency::parallel_for_each function. The basic new parallel_for_each method signature returns void and accepts two parameters: a grid<N> (think of it as an alias to extent) a restrict(direct3d) lambda, whose signature is such that it returns void and accepts an index of the same rank as the grid So it looks something like this (with generous returns for more palatable formatting) assuming we are dealing with a 2-dimensional space: // some_code_A parallel_for_each( g, // g is of type grid<2> [ ](index<2> idx) restrict(direct3d) { // kernel code } ); // some_code_B The parallel_for_each will execute the body of the lambda (which must have the restrict modifier), on the GPU. We also call the lambda body the "kernel". The kernel will be executed multiple times, once per scheduled GPU thread. The only difference in each execution is the value of the index object (aka as the GPU thread ID in this context) that gets passed to your kernel code. The number of GPU threads (and the values of each index) is determined by the grid object you pass, as described next. You know that grid is simply a wrapper on extent. In this context, one way to think about it is that the extent generates a number of index objects. So for the example above, if your grid was setup by some_code_A as follows: extent<2> e(2,3); grid<2> g(e); ...then given that: e.size()==6, e[0]==2, and e[1]=3 ...the six index<2> objects it generates (and hence the values that your lambda would receive) are:    (0,0) (1,0) (0,1) (1,1) (0,2) (1,2) So what the above means is that the lambda body with the algorithm that you wrote will get executed 6 times and the index<2> object you receive each time will have one of the values just listed above (of course, each one will only appear once, the order is indeterminate, and they are likely to call your code at the same exact time). Obviously, in real GPU programming, you'd typically be scheduling thousands if not millions of threads, not just 6. If you've been following along you should be thinking: "that is all fine and makes sense, but what can I do in the kernel since I passed nothing else meaningful to it, and it is not returning any values out to me?" Passing data in and out It is a good question, and in data parallel algorithms indeed you typically want to pass some data in, perform some operation, and then typically return some results out. The way you pass data into the kernel, is by capturing variables in the lambda (again, if you are not familiar with them, follow the links about C++ lambdas), and the way you use data after the kernel is done executing is simply by using those same variables. In the example above, the lambda was written in a fairly useless way with an empty capture list: [ ](index<2> idx) restrict(direct3d), where the empty square brackets means that no variables were captured. If instead I write it like this [&](index<2> idx) restrict(direct3d), then all variables in the some_code_A region are made available to the lambda by reference, but as soon as I try to use any of those variables in the lambda, I will receive a compiler error. This has to do with one of the direct3d restrictions, where only one type can be capture by reference: objects of the new concurrency::array class that I'll introduce in the next post (suffice for now to think of it as a container of data). If I write the lambda line like this [=](index<2> idx) restrict(direct3d), all variables in the some_code_A region are made available to the lambda by value. This works for some types (e.g. an integer), but not for all, as per the restrictions for direct3d. In particular, no useful data classes work except for one new type we introduce with C++ AMP: objects of the new concurrency::array_view class, that I'll introduce in the post after next. Also note that if you capture some variable by value, you could use it as input to your algorithm, but you wouldn’t be able to observe changes to it after the parallel_for_each call (e.g. in some_code_B region since it was passed by value) – the exception to this rule is the array_view since (as we'll see in a future post) it is a wrapper for data, not a container. Finally, for completeness, you can write your lambda, e.g. like this [av, &ar](index<2> idx) restrict(direct3d) where av is a variable of type array_view and ar is a variable of type array - the point being you can be very specific about what variables you capture and how. So it looks like from a large data perspective you can only capture array and array_view objects in the lambda (that is how you pass data to your kernel) and then use the many threads that call your code (each with a unique index) to perform some operation. You can also capture some limited types by value, as input only. When the last thread completes execution of your lambda, the data in the array_view or array are ready to be used in the some_code_B region. We'll talk more about all this in future posts… (a)synchronous Please note that the parallel_for_each executes as if synchronous to the calling code, but in reality, it is asynchronous. I.e. once the parallel_for_each call is made and the kernel has been passed to the runtime, the some_code_B region continues to execute immediately by the CPU thread, while in parallel the kernel is executed by the GPU threads. However, if you try to access the (array or array_view) data that you captured in the lambda in the some_code_B region, your code will block until the results become available. Hence the correct statement: the parallel_for_each is as-if synchronous in terms of visible side-effects, but asynchronous in reality.   That's all for now, we'll revisit the parallel_for_each description, once we introduce properly array and array_view – coming next. Comments about this post by Daniel Moth welcome at the original blog.

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  • how to make Chromium-browser start on vnc display?

    - by Oleksandr Dudchenko
    I have started Tightvncserver on Lubuntu 12.04 via the command $ tightvncserver -geometry 800x600 -depth 16 :2 VNC server successfully started and I got message like follows. New 'X' desktop is gateway:2 Starting applications specified in /home/dolv/.vnc/xstartup Log file is /home/dolv/.vnc/gateway:2.log Then I've successfully loged in from remote PC using realvncclient. Trying to start Chromium-browser from menu... no luck. There was one more attempt: I opened the LXTerminal from menu. Trying to start is from terminal with the command /usr/bim/chromium-browser & it returned the message like follows: Xlib: extention "RANDR" missing on desktop :2 I have also discovered that after my two attampts the chromium-browser has created 2 new windows on the host on which was session running on display :0 The Question: How to make the browser start on that display from which it was called (in my occasion from vnc session display)?

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  • Online ALTER TABLE in MySQL 5.6

    - by Marko Mäkelä
    This is the low-level view of data dictionary language (DDL) operations in the InnoDB storage engine in MySQL 5.6. John Russell gave a more high-level view in his blog post April 2012 Labs Release – Online DDL Improvements. MySQL before the InnoDB Plugin Traditionally, the MySQL storage engine interface has taken a minimalistic approach to data definition language. The only natively supported operations were CREATE TABLE, DROP TABLE and RENAME TABLE. Consider the following example: CREATE TABLE t(a INT); INSERT INTO t VALUES (1),(2),(3); CREATE INDEX a ON t(a); DROP TABLE t; The CREATE INDEX statement would be executed roughly as follows: CREATE TABLE temp(a INT, INDEX(a)); INSERT INTO temp SELECT * FROM t; RENAME TABLE t TO temp2; RENAME TABLE temp TO t; DROP TABLE temp2; You could imagine that the database could crash when copying all rows from the original table to the new one. For example, it could run out of file space. Then, on restart, InnoDB would roll back the huge INSERT transaction. To fix things a little, a hack was added to ha_innobase::write_row for committing the transaction every 10,000 rows. Still, it was frustrating that even a simple DROP INDEX would make the table unavailable for modifications for a long time. Fast Index Creation in the InnoDB Plugin of MySQL 5.1 MySQL 5.1 introduced a new interface for CREATE INDEX and DROP INDEX. The old table-copying approach can still be forced by SET old_alter_table=0. This interface is used in MySQL 5.5 and in the InnoDB Plugin for MySQL 5.1. Apart from the ability to do a quick DROP INDEX, the main advantage is that InnoDB will execute a merge-sort algorithm before inserting the index records into each index that is being created. This should speed up the insert into the secondary index B-trees and potentially result in a better B-tree fill factor. The 5.1 ALTER TABLE interface was not perfect. For example, DROP FOREIGN KEY still invoked the table copy. Renaming columns could conflict with InnoDB foreign key constraints. Combining ADD KEY and DROP KEY in ALTER TABLE was problematic and not atomic inside the storage engine. The ALTER TABLE interface in MySQL 5.6 The ALTER TABLE storage engine interface was completely rewritten in MySQL 5.6. Instead of introducing a method call for every conceivable operation, MySQL 5.6 introduced a handful of methods, and data structures that keep track of the requested changes. In MySQL 5.6, online ALTER TABLE operation can be requested by specifying LOCK=NONE. Also LOCK=SHARED and LOCK=EXCLUSIVE are available. The old-style table copying can be requested by ALGORITHM=COPY. That one will require at least LOCK=SHARED. From the InnoDB point of view, anything that is possible with LOCK=EXCLUSIVE is also possible with LOCK=SHARED. Most ALGORITHM=INPLACE operations inside InnoDB can be executed online (LOCK=NONE). InnoDB will always require an exclusive table lock in two phases of the operation. The execution phases are tied to a number of methods: handler::check_if_supported_inplace_alter Checks if the storage engine can perform all requested operations, and if so, what kind of locking is needed. handler::prepare_inplace_alter_table InnoDB uses this method to set up the data dictionary cache for upcoming CREATE INDEX operation. We need stubs for the new indexes, so that we can keep track of changes to the table during online index creation. Also, crash recovery would drop any indexes that were incomplete at the time of the crash. handler::inplace_alter_table In InnoDB, this method is used for creating secondary indexes or for rebuilding the table. This is the ‘main’ phase that can be executed online (with concurrent writes to the table). handler::commit_inplace_alter_table This is where the operation is committed or rolled back. Here, InnoDB would drop any indexes, rename any columns, drop or add foreign keys, and finalize a table rebuild or index creation. It would also discard any logs that were set up for online index creation or table rebuild. The prepare and commit phases require an exclusive lock, blocking all access to the table. If MySQL times out while upgrading the table meta-data lock for the commit phase, it will roll back the ALTER TABLE operation. In MySQL 5.6, data definition language operations are still not fully atomic, because the data dictionary is split. Part of it is inside InnoDB data dictionary tables. Part of the information is only available in the *.frm file, which is not covered by any crash recovery log. But, there is a single commit phase inside the storage engine. Online Secondary Index Creation It may occur that an index needs to be created on a new column to speed up queries. But, it may be unacceptable to block modifications on the table while creating the index. It turns out that it is conceptually not so hard to support online index creation. All we need is some more execution phases: Set up a stub for the index, for logging changes. Scan the table for index records. Sort the index records. Bulk load the index records. Apply the logged changes. Replace the stub with the actual index. Threads that modify the table will log the operations to the logs of each index that is being created. Errors, such as log overflow or uniqueness violations, will only be flagged by the ALTER TABLE thread. The log is conceptually similar to the InnoDB change buffer. The bulk load of index records will bypass record locking. We still generate redo log for writing the index pages. It would suffice to log page allocations only, and to flush the index pages from the buffer pool to the file system upon completion. Native ALTER TABLE Starting with MySQL 5.6, InnoDB supports most ALTER TABLE operations natively. The notable exceptions are changes to the column type, ADD FOREIGN KEY except when foreign_key_checks=0, and changes to tables that contain FULLTEXT indexes. The keyword ALGORITHM=INPLACE is somewhat misleading, because certain operations cannot be performed in-place. For example, changing the ROW_FORMAT of a table requires a rebuild. Online operation (LOCK=NONE) is not allowed in the following cases: when adding an AUTO_INCREMENT column, when the table contains FULLTEXT indexes or a hidden FTS_DOC_ID column, or when there are FOREIGN KEY constraints referring to the table, with ON…CASCADE or ON…SET NULL option. The FOREIGN KEY limitations are needed, because MySQL does not acquire meta-data locks on the child or parent tables when executing SQL statements. Theoretically, InnoDB could support operations like ADD COLUMN and DROP COLUMN in-place, by lazily converting the table to a newer format. This would require that the data dictionary keep multiple versions of the table definition. For simplicity, we will copy the entire table, even for DROP COLUMN. The bulk copying of the table will bypass record locking and undo logging. For facilitating online operation, a temporary log will be associated with the clustered index of table. Threads that modify the table will also write the changes to the log. When altering the table, we skip all records that have been marked for deletion. In this way, we can simply discard any undo log records that were not yet purged from the original table. Off-page columns, or BLOBs, are an important consideration. We suspend the purge of delete-marked records if it would free any off-page columns from the old table. This is because the BLOBs can be needed when applying changes from the log. We have special logging for handling the ROLLBACK of an INSERT that inserted new off-page columns. This is because the columns will be freed at rollback.

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  • sbackup: can not mount FTP automatically

    - by ledy
    In the sbackup configuration GUI i set the ftp://user:pw@online/storage and it's marked as successfully connected. After daily backup time, I checked the ftp and it was empty. In the error mail it says: Error in _do_mount: volume doesn't implement mount [ERROR_NOT_SUPPORTED - Operation not supported for the current backend.] Unable to mount: volume doesn't implement mount File access manager not initialized When restarting the sbackup GUI, it is no longer connected to the ftp and i have to click the button again to connect the remote directory - although it still knows my user/pw. How to save this permanently?

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  • PXE-boot for Ubuntu 10.04 Desktop version

    - by omkar
    My aim is to Install the Ubuntu 10.04 desktop version on a remote machine using PXE-BOOT. I'm trying to apply the steps given in PXE-BOOT for Ubuntu 9.10 . (I know this is for 9.10). In "Step 8. Setting Up Boot Files", it says cp -a /media/cdrom/install/netboot/* /tftpboot/ but I wasn't able to find the netboot folder in my Ubuntu 10.04 Desktop CD-Rom. Does that folder only exist in Ubuntu Server edition? Is it possible to do this in the Desktop edition?

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  • Sound notification over SSH

    - by Lekensteyn
    I just switched from the Konversation IRC client to the terminal based IRSSI. I'm starting IRSSI on a remote machine using GNU screen + SSH. I do not get any sound notification on new messages, which means that I've to check out IRSSI once in a while for new messages. That's not really productive, so I'm looking for an application / script that plays a sound (preferably /usr/share/sounds/KDE-Im-Irc-Event.ogg and not the annoying beep) on my machine if there is any activity. It would be great if I can disable the notification for certain channels. Or, if that's not possible, some sort of notification via libnotify, thus making it available to GNOME and KDE.

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  • WebLogic Application Server: free for developers!

    - by Bruno.Borges
    Great news! Oracle WebLogic Server is now free for developers! What does this mean for you? That you as a developer are permited to: "[...] deploy the programs only on your single developer desktop computer (of any type, including physical, virtual or remote virtual), to be used and accessed by only (1) named developer." But the most interesting part of the license change is this one: "You may continue to develop, test, prototype and demonstrate your application with the programs under this license after you have deployed the application for any internal data processing, commercial or production purposes" (Read the full license agreement here) If you want to take advantage of this licensing change and start developing Java EE applications with the #1 Application Server in the world, read now the previous post, How To Install WebLogic Zip on Linux!

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  • Android application Database Framework

    - by Marek Sebera
    When creating mobile (specially Android) application, I usually come to touch with similar pattern of working with data. Usually I need to fetch some remote data (covered by authorization process) to local cache. And on next request: Check networking Check presence of cache file Check version of cache file (if networking) Get new version and save cache (if networking and file not in cache, or outdated) Data store is no-SQL JSON Document-Based (and yes, I know about CouchDB Android version, but it doesn't fit my needs yet.) Process of authorizing to data source and code for check version of local cache is adapted to application. But the other code (handling network, saving cache, handling exceptions,...) is always the same. Is there any Data Store helper I can use, which provides functions I described above?

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  • How to create a restricted SSH user for port forwarding?

    - by Lekensteyn
    ændrük suggested a reverse connection for getting an easy SSH connection with someone else (for remote help). For that to work, an additional user is needed to accept the connection. This user needs to be able to forward his port through the server (the server acts as proxy). How do I create a restricted user that can do nothing more than the above described? The new user must not be able to: execute shell commands access files or upload files to the server use the server as proxy (e.g. webproxy) access local services which were otherwise not publicly accessible due to a firewall kill the server Summarized, how do I create a restricted SSH user which is only able to connect to the SSH server without privileges, so I can connect through that connection with his computer?

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  • Code to simulate a users actions, such as logging in

    - by Gortron
    I've recently begun working on a PHP application, replacing another developer. I believed the application was using an API to communicate with a remote service but when I looked through the code I found that it was using a set of functions to actually log in, fill out forms and submit them as a user might do in a browser. My intention is to replace this code, to use the services API instead. I've considered leaving the code as is and not replace it. It makes me wonder though is this a common practice in the software industry? To have a programme simulate a users actions in a browser to perform a set of actions? It feels to me that this is clever but poor programming, Have any other developers seen this?

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