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  • Posted on Monday December 11, 2017
    Announced at Google for India event, the Android Oreo (Go Edition) has hit a major milestone. It aims to give a unified Google experience to internet users especially on the low-end handsets. Much like Apple’s AirDrop, Files Go lets you transfer files directly between devices (at speeds up to 125Mbps) without it costing mobile data. This means as long as both devices have the app installed, files can be transferred on the direct basis. » 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_2.0Speed: » Read more Continue Reading »
  • Posted on Saturday March 18, 2017
    Building Linux kernel may sound a complex and geek-only thing. However, as Linux kernel itself has much less depended tools/packages compared to other software packages, it is quite easy to compile, build and install a Linux kernel from the source code in an existing Linux OS. Building Linux kernel is needed if you need to build a specific Linux kernel or update your drivers for a kernel by yourself. » Read more Continue Reading »

Latest QA answers

  • 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 targetWay 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 -tulpnRemember 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 »
  • Posted on Sunday November 26, 2017
    To test whether a script's STDERR (or STDOUT) is redirected to a file, check by [[ -f /dev/stderr ]]A process' STDOUT and STDERR are /dev/stdout and /dev/stderr and testing them with -f in Bash can judge whether they are redirected to files. An example: $ cat check-stdout-stderr.sh #!/bin/bash# Author: Eric Zhiqiang Ma[[ -f /dev/stderr ]] && echo "STDERR is a file: $(readlink -f /dev/stderr)" [[ -f /dev/stdout ]] && echo "STDOUT is a file: $(readlink -f /dev/stdout)"Tries: $ ./check-stdout-stderr.shoutputs nothing. $ ./check-stdout-stderr.sh >/tmp/a $ cat /tmp/a Continue Reading »
  • Posted on Sunday November 26, 2017
    The problem is solved by: 1, add at least one section in your main.tex; 2, in your added section, at least have one citation, otherwise there will be error "I found no \citation commands---while reading file main.aux ". Very stupid problem... Continue Reading »
  • Posted on Thursday November 23, 2017
    In a Symmetric Multiprocessor, the architectural “distance” to any memory location is the same for all processors, i.e. “symmetric”. In a NonUniform Memory Access machine, each processor is “closer” to some memory locations than others; i.e. memory is partitioned among them Asymmetrically. From my understanding, most of current architectures are SMP+UNMA if we consider cache is also part of memory hierarchy. Part of above answers are copied from https://www.quora.com/What-is-the-difference-between-SMP-and-NUMA-architectures Continue Reading »
  • Posted on Tuesday November 21, 2017
    Tested on Linux Ubuntu 14.04 Trusty > sudo apt-get install dmidecode > sudo dmidecode -s system-serial-number Continue Reading »
  • Posted on Sunday November 19, 2017
    login without PWD: add PC A's public key to PC B's authorized keys. > a@A:~> cat .ssh/id_rsa.pub | ssh b@B 'cat >> .ssh/authorized_keys' > b@B's password:Run command remotely ssh root@MachineB "ls"NOTE: running commands remotely is dangerous since there might be some ENVIRONMENT conflicts. Continue Reading »
  • Posted on Saturday November 18, 2017
    Copied from https://tex.stackexchange.com/questions/53235/why-does-latex-bibtex-need-three-passes-to-clear-up-all-warnings. The reason is as follows: 1, At the first latex run, all \cite{...} arguments are written in the file document.aux. 2, At the bibtex run, this information is taken by bibtex and the relevant entries are put into the .bbl file, sorted either alphabetically or by citation order (sometimes called "unsorted") and formatted according to the instructions provided by the bibliography style that's in use. 3, At the next run of latex, the .bbl file is included at the point the \bibliography instructions, and the correct labels for \cite{...} Continue Reading »
  • Posted on Friday November 17, 2017
    I would recommend meld for Windows users. Meld is a visual diff and merge tool open source software.meld is available on Linux, Windows and Mac OS X. Continue Reading »
  • Posted on Wednesday November 15, 2017
    In a work-conserving mode, the scheduler must choose one of the pending requests, if any, to dispatch, even if the pending requests are far away from the current disk head position. The rationale for non-work-conserving schedulers, such as the anticipatory scheduler (AS) and Completely Fair Queuing (CFQ), is that a request that is soon to arrive might be much closer to the disk head than the currently pending requests, in which case it may be worthwhile to wait for the future request. In my point view, non-work conserving keeps the locality of synchronous I/O requests so that the system Continue Reading »
  • Posted on Tuesday November 14, 2017
    For example, to change date to 14 Nov 2017 11:57:00, the command would be, $ sudo date --set "14 Nov 2017 11:57:00" Tue Nov 14 11:57:00 HKT 2017 Continue Reading »
  • Posted on Tuesday November 07, 2017
    Your permission bits may be turned off by umask. Try to make umask 000 first: import os# make dirs with mode def mkdir_with_mode(directory, mode): if not os.path.isdir(directory): oldmask = os.umask(000) os.makedirs(directory, 0777) os.umask(oldmask)It will clear the umask first so that the mode provided takes full effect. Continue Reading »
  • Posted on Wednesday October 18, 2017
    alien is already in EPEL and it makes it quite easy to install it in CentOS 7. First, enable EPEL following this tutorials. Then, install alien by # yum install alienThen alien should be ready: # yum info alien Installed Packages Name : alien Arch : noarch Version : 8.95 Release : 3.el7 Size : 223 k Repo : installed From repo : epel Summary : Converter between the rpm, dpkg, stampede slp, and Slackware tgz file formats URL : https://sourceforge.net/projects/alien-pkg-convert/ License : GPLv2+ Description : Alien is a program that converts between the Continue Reading »
  • Posted on Wednesday October 18, 2017
    I don't think GNOME 3 or GNOME 3 classic has this function available or there any plugins that supports so. If you need this function that the panel can hide automatically, you may consider another desktop environment, such as MATE, that supports so. This may not solve your problem. But it's just an alternative way to support the need. Continue Reading »
  • Posted on Thursday September 14, 2017
    2 possible ways: /forcefsck way for / # touch /forcefsckand reboot. Next time the / will be fsck'ed . systemd way Add these 2 kernel boot parameters: fsck.mode=force fsck.repair=yesWhat these 2 kernel parameters do: KERNEL COMMAND LINEsystemd-fsck understands one kernel command line parameter:fsck.mode=One of "auto", "force", "skip". Controls the mode of operation. The default is "auto", and ensures that file system checks are done when the file system checker deems them necessary. "force" unconditionally results in full file system checks. "skip" skips any file system checks.fsck.repair=One of "preen", "yes" Continue Reading »
  • Posted on Tuesday September 12, 2017
    On CentOS 7 Linux it is usually by default /var/lib/mysqlBut here I give you another "hacky" way to find it out. The method is to find out the mysql daemon mysqld' opened files and the paths because it must open the files to read/write data. First, find out the process ID of the mysqld process: # ps aux | grep mysqldmysql 25403 1.0 17.2 1322220 174948 ? Ssl Aug31 178:10 /usr/sbin/mysqldSecond, go to the mysqld process' dir under /proc/. For the above example, # cd /proc/25403/Check the opened files under the directory Continue Reading »
  • Posted on Tuesday September 12, 2017
    You can check this tutorial for how to force a checkpointing of metadata in HDFS: How to force a metadata checkpointing in HDFS Continue Reading »
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