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  • Posted on Sunday December 31, 2017
    Evolution is a great personal information management tool that provides Email, address book and calendar tools. Evolution provides many enterprise friendly feature such as native support to Microsoft Exchange connectivity for Emails, address books and calendars. Evolution uses various ways including plain files and dconf configuration systems. This post will give an introduction to the common locations or paths where Evolution stores its data and configuration files in Linux. » Read more Continue Reading »
  • Posted on Saturday December 16, 2017
    We ever discussed fixing ports used by NFSv3 so that it can be easily exported to external networks. For NFSv4.1 or higher, things are much easier. The ports for mountd, statd, and lockd are not required in a pure NFSv4 environment. We have less ports to control or allow for connections. Only port 111 and 2049 need to be taken care of for NFSv4. » Read more Continue Reading »
  • Posted on Monday December 11, 2017
    This blog will explain about how to add a custom content in a Receipt which will be generated from MPOS in Microsoft Dynamics. Microsoft provides us with certain fields which can be put into the receipt. There are certain fields which a client will ask to show in the receipt. If the desired field is not available in the standard receipt designer, we have to customize it. » Read more Continue Reading »
  • Posted on Saturday November 25, 2017
    Introduction Load balance is used to rebalance the whole system resources (eg, CPU, memory, etc) so that system performance, scalability (in terms of no matter how many processes contend) and usability (in terms of idle resources can be used up immediately) will be improved. In this article, I mainly present how load balance for CPU reosurces works inside operating systems like Linux Kernel (v4.7.4). » Read more Continue Reading »
  • Posted on Tuesday November 21, 2017
    What surprises are awaiting the tech world with .NET Core 2.1 Release in 2018? Technology is one of the most dynamic spheres these days. Every single year you will find a new version of an existing software and .NET Core is not an exception. The intentions of these upgradation is to make online activities seamless, daily work hassle free and to bring the world within our easy reach. » Read more Continue Reading »
  • Posted on Tuesday November 14, 2017
    Quick links to some useful software on Windows including Web browsers, Video/audio player and ssh/scpsftp/vnc tools for connecting to Linux. ssh/scp/sftp/vnc for connecting to Linux For Linux users, it is sometimes unavoidably to use Windows. With Windows, the Linux users will need to connect to Linux for some tasks. Some general software are needed. The most common ones may be ssh/scp/sftp/vnc. » Read more Continue Reading »
  • Posted on Thursday September 21, 2017
    Technology Hibernate Envers is the frameworks for auditing entities. As the name suggests Hibernate Envers is developed on top of Hibernate, it will on Hibernate and Hibernate implemented JPA. Hibernate Envers provides easy auditing, versioning solution for entity classes. Advantages of Hibernate Envers: Auditing of all mappings defined by JPA specification. Auditing Hibernate specific mappings which extends the JPA specification. Logging data for each revision using revision entity. » Read more Continue Reading »
  • Posted on Monday September 18, 2017
    Introduction In this tutorial, we will be learning as how to deploy .NET Core 2.0 MVC web application on Microsoft Public Cloud i.e. Microsoft Azure, using Microsoft Visual Studio 2017 v15.3 For novice Cloud developers, aspiring .NET / Cloud architects, and all other IT professionals associated with the .NET Core framework & Cloud computing, especially with Microsoft Azure, this tutorial will explain the importance and capabilities of newly released . » Read more Continue Reading »
  • Posted on Saturday September 09, 2017
    The encoding of x86 and x86-64 instructions is well documented in Intel or AMD’s manuals. However, they are not quite easy for beginners to start with to learn encoding of the x86-64 instructions. In this post, I will give a list of useful manuals for understanding and studying the x86-64 instruction encoding, a brief introduction and an example to help you get started with the formats and encodings of the x86-64 instructions. » Read more Continue Reading »
  • Posted on Saturday September 09, 2017
    The metadata checkpointing in HDFS is done by the Secondary NameNode to merge the fsimage and the edits log files periodically and keep edits log size within a limit. For various reasons, the checkpointing by the Secondary NameNode may fail. For one example, HDFS SecondaraNameNode log shows errors in its log as follows. 2017-08-06 10:54:14,488 ERROR org.apache.hadoop.hdfs.server.namenode.SecondaryNameNode: Exception in doCheckpoint java.io.IOException: Inconsistent checkpoint fields. » Read more Continue Reading »
  • Posted on Sunday August 27, 2017
    Introduction In general, if we want to debug Linux Kernel, there are lots of tools such as Linux Perf, Kprobe, BCC, Ktap, etc, and we can also write kernel modules, proc subsystems or system calls for some specific debugging aims. However, if we have to instrument kernel to achieve our goals, usually we would not like to pay more efforts like above solutions since we’d like to achieve our aims quickly and easily. » Read more Continue Reading »
  • Posted on Saturday August 26, 2017
    Introduction As we know, network subsystems are important in computer systems since they are I/O systems and need to be optimized with many algorithms and skills. This article will introduce how QEMU/KVM [2] network part works. In order to put everything simple and easy to understand, we will begin with several examples and then understand how it works internally. Examples In this example, we will use TAP device [1] as QEMU/KVM host network device driver and VirtIO driver will be used to send/receive network packets/data between Host OS and Guest OS. » Read more Continue Reading »
  • Posted on Sunday August 20, 2017
    Abstract Most popular task monitor systems (such as top, iotop, proc, etc) can only get tasks’ disk I/O information like tasks’ I/O utilization percentage every seconds due to kernel timer/tick frequency and high time cost of system interfaces. This article presents I/O Microscopy, a new way to get tasks’ disk I/O information with high accuracy. Experiments show that I/O microscopy can filter out I/O intensive tasks effectively. » Read more Continue Reading »
  • Posted on Saturday August 12, 2017
    With Google algorithm becoming more intelligent with each passing day, the margin for errors has significantly reduced over the past decade. Back in the day, you might get away with keyword stuffing but today, the same offense will strike off your website from Google search engine results. No one wants that, right. To save you from such a situation, here are ten common mistakes that most casual followers of the industry are making but should not. » Read more Continue Reading »
  • Posted on Tuesday July 25, 2017
    The word “viral” has received a lot of attention over the last few years and is applied to different types of content to describe how quickly it has spread and gained popularity. Many times, you’ll hear people speak about their idea and how fast it will spread while assuming that it will “go viral”, but they never seem to understand how they’re going to make it go viral. » Read more Continue Reading »
  • Posted on Friday May 12, 2017
    Call forwarding is useful if you are expected to be unavailable for receiving calls or lose cell phone coverage for some time. Call forwarding is not something that is "new" to modern phones. It is a feature which is invented in 1960s (the patent expired in 1980) of some telephone switching systems. But with iPhone/iOS, there is a convenient call forwarding feature in iOS for you to set up call forwarding to forward calls to a landline or other phone by its number or disable the call forwarding. » Read more Continue Reading »
  • Posted on Thursday April 20, 2017
    HTML supports many characters/symbols such as mathematical symbols, and currency symbols. They are not present on a normal keyboard. And some of these characters may have special meanings for formatting text. To add such characters / symbols to an HTML text, you can use an HTML entity name or an entity number in decimal or hexadecimal. This post list many special Characters in HTML as a friendly reference. » Read more Continue Reading »
  • Posted on Tuesday April 18, 2017
    From a small business owner, a blogger, a student or individual with a personal project, the need to create websites has never been more prominent. Having a basic understanding of HTML and canvas knowledge can be helpful, and it is simple to master. The thought of learning to code and programming may seem a long and daunting task, but some people may be surprised to know that it need not be as scary as it sounds. » Read more Continue Reading »
  • Posted on Saturday April 15, 2017
    This post introduces how to install a paravirtualized CentOS 7 DomU on Xen. The very common way of installing DomU does not work for CentOS 7. A little trick to set the repository and the network used by the VM should be used by adding a setting strings to the “extra=” field for this VM. Note that this tutorials was tested with CentOS 7.2 (1511). » Read more Continue Reading »
  • Posted on Sunday April 09, 2017
    The USB standards have evolved to 3.1 and the supported throughput have been increased too. On Linux, the support to USB standards are following the standards development. In this post, we will survey the standards that common hardware support and the support in Linux. USB standards USB 2.0: https://en.wikipedia.org/wiki/USB#USB_2.0 Speed: » Read more Continue Reading »

Latest QA answers

  • Posted on Thursday February 01, 2018
    In C++11, you may let the compiler infer the type for you by using decltype(...) and replace the type declaration with decltype(). For example #include <iostream> #include <string> #include <algorithm> int main () { std::vector<std::string> ss = {"hello", "world"}; std::transform(std::begin(ss), std::end(ss), std::begin(ss), [](decltype(*std::begin(ss)) si) { return si; }); return 0; } decltype(*std::begin(ss)) infers the concrete type automatically for you so that you don't need to manually write the concrete type delcaration. Continue Reading »
  • Posted on Wednesday January 24, 2018
    If a packet is forwarded by iptables (e.g. by a rule in PREROUTING chain) https://www.systutorials.com/816/port-forwarding-using-iptables/ , it will go through the FORWARD chain. Continue Reading »
  • Posted on Sunday January 07, 2018
    To access the data of a const map in C++, use the at() member function, const mapped_type & at (const key_type &__k) const instead of operator[]. The reason why operator[] can not be used for a const map is because that, if the key from operator[] does not exist, a pair with that key is created using default values and then returned, which will actually change the map. Note that at() may throw std::out_of_range exception if no such data is present. For the code in the question, to make it work, change std::int64_t count(const std::map<std::string Continue Reading »
  • Posted on Friday January 05, 2018
    The private IP (lan IP) is likely the Extended HELLO (EHLO) or HELLO (HELO). You can change the HELO message: Go to Thunderbird's about:config page (in Preferences > Advanced > General > Config Editor). Find the mail.smtpserver.default.hello_argument preference (create it by right-clicking > New > String if it doesn't exist yet). Enter localhost as its value. Then that field in the Email header will contains localhost instead of your private IP. One example for your reference: Received: from localhost (example.com [1.3 Continue Reading »
  • Posted on Tuesday January 02, 2018
    You may add these lines to your vimrc for C/C++ to indent lambdas correctly as you listed above setlocal cindent " handle lambda correctly setlocal cino=j1,(0,ws,Ws The key is setting cino (cinoption) to be j1,(0,ws,Ws. jN is new in Vim 7.4 for "indent Java anonymous classes correctly" which improves C/C++ lambda indenting too. Check my vimrc as an example. Continue Reading »
  • Posted on Tuesday January 02, 2018
    In short, use this code snippet: input.erase(std::remove(input.begin(), input.end(), '\n'), input.end()); std::remove() shifts all elements that are equal to the value \n by moving the elements in the range to the end and returns the past-the-end iterator for the new range of values that are not \n. std::erase() removes elements from the container in the range specified and updates the size of the vector. For the above piece of code, the range of elements removed are all \ns. A full example program, #include <iostream> #include <algorithm> int main () { std::string Continue Reading »
  • Posted on Tuesday December 26, 2017
    parted has a unit command to specify the unit to use. unit unit Set unit as the unit to use when displaying locations and sizes, and for interpreting those given by the user when not suffixed with an explicit unit. unit can be one of "s" (sectors), "B" (bytes), "kB", "MB", "MiB", "GB", "GiB", "TB", "TiB", "%" (percentage of device size), "cyl" (cylinders), "chs" (cylinders, heads, sectors), or "compact" (megabytes for input, and a human-friendly form for output). For sectors, the unit is "s". To print the stand and end sections of a disk such as sda Continue Reading »
  • Posted on Tuesday December 26, 2017
    Evolution supports the contact autocompletion. To enable it, do as follows in Evolution. In Evolution Preferences dialog, in the "Contacts" section's "General" tab, select the "Always show address of the autocompleted contact" under the Autocompletion part. Continue Reading »
  • Posted on Tuesday December 26, 2017
    Evolution does not have (so far) "Flowing Text" mode where "the text is soft broken at the composer edge, but those soft breaks aren't translated to hard breaks when the mail is sent" ( Reference: https://mail.gnome.org/archives/evolution-list/2017-April/msg00079.html ) as in other editors or Email clients like Thunderbird. You may have several alternative ways though. Format the Email as Preformated for Plain Text Emails The receiver side Email client and wrap the text as they prefer to. The problem left is that the editing of the Emails for Preformated text in Evolution is painful. 2 possible Continue Reading »
  • Posted on Monday December 25, 2017
    Evolution has a function to "apply the same view settings to all folder" so that the same sorting ways are kept for all folders. To set it, in "Edit" -> "Preference" to open the Evolution Preferences dialog. In the "Mail Preferences" page's "Genera" tab, you can set this to be selected to enable it. Continue Reading »
  • Posted on Saturday December 23, 2017
    Do according to [1]. NOTE: on Ubuntu, remember to restart ssh service like this "sudo restart ssh". [1] https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/v2v_guide/preparation_before_the_p2v_migration-enable_root_login_over_ssh Continue Reading »
  • Posted on Saturday December 23, 2017
    The Litum Info Lite free app (Litum Info full version app) can show you the info of CPU including its frequency. The CPU frequency: You can find the CPU info page from the menu: Continue Reading »
  • Posted on Friday December 22, 2017
    Like you, I want to have one and only one mail filter set. This can be done, at least on Linux. Go to the directory, /home/[username]/.thunderbird/[random].default/ sudo find / -iname "msgFilterRules.dat" will show you all the filters as described by others. Pick whichever one you want to be the main one. I chose ./Mail/Local Folders/msgFilterRules.dat, which is the rule in the Local Folders directory that I don't otherwise use. Copy the one you want every account to use into this directory. Go to each mail directory and enter the command: ln -bsv ../../Mail/Local\ Continue Reading »
  • Posted on Friday December 22, 2017
    Just enter CTRL+r The function of above is: (reverse-i-search)`': It is very fast and efficient. Continue Reading »
  • Posted on Friday December 15, 2017
    In Python 3: To print to STDOUT print("your message") To print to STDERR print("your message", file=sys.stdout) To use Python 3 style print in Python 2: In Python 3: To print to STDOUT from __future__ import print_function print("your message") To print to STDERR from __future__ import print_function print("your message", file=sys.stdout) Continue Reading »
  • Posted on Wednesday December 06, 2017
    The default goal of make is the first target whose name does not start with '.' if .DEFAULT_GOAL is not set. Ref: make manual. To set the default target to 'default' as an example being not the first target in the Makefile, you have at least 2 ways. Way 1. Set the .DEFAULT_GOAL special variable to 'default'. .DEFAULT_GOAL := default # other targets ... default: @ echo default target Way 2. clear the .DEFAULT_GOAL special variable before the 'default' target so that 'default' turns to the first target after .DEFAULT_GOAL is not set. # other targets Continue Reading »
  • Posted on Tuesday December 05, 2017
    # netstat -tulpn Remember to run this program with root permission since some programs can only be accessed by root. Continue Reading »
  • Posted on Tuesday November 28, 2017
    List all shared memories in your Linux Systems > $ ipcs -m Delete specific one > $ ipcrm -M 0x0001869c Continue Reading »
  • Posted on Tuesday November 28, 2017
    UEFI is the advanced BIOS, which solves some limitations in BIOS such as 1, 16-bit processor mode; 2, 1 MB addressable space and PC AT hardware. References: https://en.wikipedia.org/wiki/Unified_Extensible_Firmware_Interface Continue Reading »
  • Posted on Sunday November 26, 2017
    You may try Encdroid a piece of free software released under the GNU General Public License. It is an Android application. It can access EncFS volumes on cloud storage or internal/USB storage devices. Google Play Store Link: https://play.google.com/store/apps/details?id=org.mrpdaemon.android.encdroid&hl=en Source code: https://github.com/mrpdaemon/encdroid Continue Reading »
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