How to Compile and Install Linux Kernel from the Source Code in an Existing Linux OS

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

Make Better Decisions for Your Businesses with Data Visualization

Header In today’s time, data visualization has become a significant part of the success story of an organization. With the help of right techniques, visualizing data can reveal insights which the management staff can use in their decision-making in order to make sound data-driven decisions. Mapping software is among the robust data visualization tools that you can avail today. With maps, you can find stories, trends, and insights that cannot be found in spreadsheets. » Read more

Are You Wanting to Learn a Programming Language? Read Before Your Make a Choice

Programming LanguagesMaking a career choice is difficult. And, if you have decided on becoming a programmer, the difficulty is just beginning. The most important thing is to first decide the language that you want to learn and this is often the most difficult decision. The good part is that you know you need to focus on learning programming and the bad part is that you might still be thinking which programming language should you begin to learn. » Read more

Vim Tutorial for Beginners: vimtutor

There are many Vim tutorials and Vim tips on the Web. However, I find the vimtutor provides the best tutorial among those so far as I found on the Web while the vimtutor seems usually reachable from a terminal which is not obviously known to Vim beginners who are usually Linux beginners too. This page shows the content of the Vim tutorial from the command vimtutor in a web page which is especially easier for Vim beginners to get and learn. » Read more

How to Install 32-bit Wine on CentOS 7

Since version 7, RHEL has only x86-64 versions. The same thing happens to CentOS 7. In CentOS 7/EPEL, there is only package for Wine x86-64. However, many Windows .exe files are 32-bit. Even there are 64-bit versions for some software, their installation file is 32-bit. And for some certain software such as Office 2007, 32-bit wine is preferred. In this post, we will check how to install 32-bit Wine 1.8 on CentOS 7. » Read more

How to Change Systemd Boot Target on Linux

Many Linux distros, such as RHEL/CentOS 7, Fedora, Ubuntu 16, are now using systemd instead of init as the init system. It is common for Linux users to set Linux to boot to “GUI” or “Text” mode. The old way of changing ‘/etc/inittab’ for choosing Linux runlevels is not working for sytemd. This post will introduce the way for systemd systems to select the “runlevels”. » Read more

How to Keep Linux SSH Session Alive from Disconnecting – Server and Client Side Fixes

SSH is a very common tool for Linux/Unix platforms. One annoying problem when using SSH is that the connection may get disconnected if the SSH connection is idle for some time under common configurations. Users may run an infinite loop like while true; do uptime; sleep 30; done when there is no work to be done in a SSH session. There are better ways as SSH servers and clients already provide such support and we will discuss these methods in this post. » Read more

Which Checksum Tool on Linux is Faster?

It is common practice to calculate the checksums for files to check its integrity. For large files, the checksum computation is slow. Now I am wondering why it is so slow and whether choosing another tool will be better. In this post, I try three common tools md5sum, sha1sum and crc32 to compute checksums on a relatively large file to see which checksum tool on Linux is faster to help us decide the choices of the checksum tool. » Read more

Running a Command Upon Files or Directories Changes on Linux

Doing actions upon changes of files and directories is very useful. Examples like compiling a project after the source code files are changed, sending emails after important configuration files are modified, building the PDF after a TeX file is modified. On Linux, the inotify-tools provide good support for trigger actions after changes. In this post, I will introduce a small tool which continuously runs a command upon certain files and directories change. » Read more

How to Regenerate Grub2 Config Files on Linux

Grub2 config file may need to be re-generated after changing Grub2 configurations such as configuration changes and setting default boot entries. The Grub2’s config file may be at different locations depending on your Linux distro and whether your Linux is booted in BIOS or UEFI mode. This makes regenerating Grub2 config file not easy for Linux users especially beginners. In this post, I will introduce a way that should be portable and easy to use. » Read more

Getting Rid of DTS/AC3 Audio using ffmpeg on Linux to Play MKV Files on iOS or Android

I encountered the problem on iPhone that MKV video files with AC3 are played with no sound. The OPlayer reports to me that “According to DTS patent, DTS is forbidden to play , None of the media player on iPhone/iPad can play DTS”. dts-ac3-on-mobile.png However, the video file can be played in MPlayer on Linux just well. Checking MPlayer’s output: ========================================================================== Opening audio decoder: [ffmpeg] FFmpeg/libavcodec audio decoders [ac3 @ 0x7ff826946dc0]Channel layout '5.1(side)' with 6 channels does not match specified number of channels 2: ignoring specified channel layout AUDIO: 48000 Hz, 2 ch, floatle, 640.0 kbit/20.83% (ratio: 80000->384000) Selected audio codec: [ffac3] afm: ffmpeg (FFmpeg AC-3) ========================================================================== Here, “Selected audio codec: [ffac3] afm: ffmpeg (FFmpeg AC-3)” indicates that the audio is encoded in AC-3. » Read more

Profiling Vim to Find Out Which Plugin Makes Vim Slow

Vim is pretty fast and powerful. However, the core of Vim is (yet) single-threaded (some discussions and tries on porting Vim to be multi-threading, but not yet there). This means some functions that are slow will block Vim there and you have to wait for it. While Vim is fast, some plugins are not. When Vim turns to be slow, it is very likely caused by one or more plugins. » Read more

Blocking JavaScripts from a Site in Chrome in 2 Easy Steps

You may be aware of the GitHub’s largest DDoS attack in history on Mar. 27, 2015 (some context, technical details, and discussions):We've been under continuous DDoS attack for 24+ hours. The attack is evolving, and we're all hands on deck mitigating. — GitHub Status (@githubstatus) March 27, 2015 One important technique when facing this kind of problems is blocking certain sites’ JavaScripts in your browser. » Read more

How to Print PowerPoint Poster by HP Designjet 500 Plotter

First time getting my hand on a plotter (HP Designjet 500) directly to print a poster, I found it was an interesting experience. But configuring the printer settings was not that straightforward compared to using normal office A4 printers. I took photos of how it was configured for reference of my own and also those who may need it. First, here is a picture of the HP Designjet 500 plotter, a pretty big printer. » Read more

Changing iPhone Holiday Calendar to Your Local One

I usually use iPhone in the English language. However, I find the iPhone calendar app includes a US holiday calendar subscribed while I am not in US and displaying US holidays in the iPhone calendar is no use and kind of annoying to me. holiday-calendar-iphone-us.png After some investigation, I find the way to set the iPhone holiday calendar to the local or specific one. » Read more