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Archive for September, 2017

screenkey

September 30, 2017 Leave a comment

screenkey is a screencast tool to display your keys, thus your viewers can see exactly what keys you pressed.

Here is a screenshot:

And here is a short youtube video about it from gotbletu: link.

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Categories: linux Tags: ,

Setting the number of open files

September 29, 2017 Leave a comment

Problem
I installed Neo4j and when I started the server, I got a warning message: “Max 1024 open files allowed, minimum of 40 000 recommended.”

How to increase the number of open files?

Solution
With “ulimit -n” you can check the current value of the number of open files. By default, it’s 1024. To increase this value, follow these steps:

Open /etc/security/limits.conf and add these lines:

root   soft    nofile  40000
root   hard    nofile  40000
jabba  soft    nofile  40000
jabba  hard    nofile  40000

Here, instead of “jabba” use your account name. I use my Linux box under the user name “jabba”.

Open /etc/pam.d/su and add this line:

session    required   pam_limits.so

Restart your machine so that these changes take effect. Re-run “ulimit -n“; now it should display 40000.

Categories: bash Tags: , ,

Replace your legacy extensions in Firefox

September 27, 2017 Leave a comment

Firefox will switch to a new extension technology and extensions built with the old technology won’t be supported. You must have noticed that several of your add-ons are labeled as “legacy”. More info here.

The site https://mozilla.github.io/extension-finder/ allows you to find a compatible replacement for your Firefox legacy extension.

Categories: firefox Tags: , ,

[windows 7] unauthorized changes on the firmware, operating system, or UEFI drivers

September 25, 2017 Leave a comment

Problem
A friend called me last week that he has a problem with his PC. He has Windows 7 and after installing some updates, the system couldn’t reboot. He got the following error message:

(Screenshot from here.)

Solution
I found the solution here. In a nutshell: enter BIOS -> Boot -> Secure Boot. Next to “OS Type” you must have Windows. Change it to “Other OS”. Save and reboot.

Categories: windows Tags: , , , ,

simplescreenrecorder

September 24, 2017 Leave a comment

Problem
Under Linux you want to do some screen capturing. For instance, you want to do some tutorial videos.

Solution
I used gtk-RecordMyDesktop for a long time, but my current favorite is simplescreenrecorder. With gtk-RecordMyDesktop I could only save in .ogv format that I had to convert to .mp4 with ffmpeg. simplescreenrecorder can save directly in mp4 format.

Adobe Premiere Pro CS6
For editing my videos, I started to use Adobe Premiere Pro CS6. First, I asked my friends, and most of them suggested this. Second, I found some good and detailed tutorial videos for this software. I’m a newbie in video editing, so I needed some tutorials that showed everything step by step.

However, in Premiere Pro I ran into a problem. You need to import a video file and pull it to the timeline if you want to edit it. However, when I pulled an mp4 file, the audio track didn’t appear on the timeline. I had a workaround solution: from my .mp4 I extracted the audio in .wav format (with ffmpeg), and pulled it to the audio track. Strangely, the audio track was often a little bit shorter than the video track. But it was just annoying, it didn’t cause a problem.

So I tried some other screen capturing tools next to gtk-RecordMyDesktop, and that’s how I found simplescreenrecorder. After several trial and errors, I figured out why the audio track was missing. Whether the audio track appears or not depends on the audio codec! If you save the audio in AAC format, then Premiere Pro will like it and the audio track will appear when you pull such an .mp4 on the timeline. The good news is that you can select in simplescreenrecorder what audio codec you want to use!

Screenshots
Here are some screenshots of my simplescreenrecorder setup:

Alternatives
For some more screen capturing tools, see this post: 5 Best Screen Capture Tools for Linux.

Java 9 got a REPL

September 23, 2017 Leave a comment

Java 9 came out a few days ago and it includes a REPL. This is a well-known thing among interpreted languages (e.g. Python), but it’s not very common in the case of compiled languages.

$ jshell
|  Welcome to JShell -- Version 9
|  For an introduction type: /help intro

jshell> int a = 3
a ==> 3

jshell> int b = 2
b ==> 2

jshell> a + b
$3 ==> 5

jshell> $3
$3 ==> 5

jshell>

Here is a more detailed blog post about jshell.

Note
jshell stands for Java Shell, and not for JavaScript Hell!

Categories: java Tags: , ,

Introduction to Linux

September 23, 2017 Leave a comment

I want to start a new video series entitled “Introduction to Linux”. It is intended for beginners who never (or not much) used Linux before. So far I have one video, but I plan to add more videos in the future. I will update this post with the new videos.

Complete playlist: here.

Videos in the series:

Categories: linux, ubuntu Tags: ,