Beginning version 7, Vim started to introduce its auto-complete feature. By default it works by being able to auto-complete words that already existed in the file being edited. If enabled, it can also auto-complete syntax for various programming languages.

To use the Vim auto-complete feature, just hit Ctrl + n while in insert mode, and you’ll get a list of word suggestions as in the following example;

To make the list cycle backwards, hit Ctrl + p. You can also use the arrow keys to move up and down the list.

A network switch doesn’t foward packets to everyone in the network the same way as a network hub do, and so theoretically a person in the network cannot look at other person’s traffic. There are ways however to get through this problem, which is by performing arp spoofing.

tar.bz2 is normally the default extension for bzip2-compressed tar archive. bzip2 compression produces smaller files but requires higher CPU power to compress and extract compared to most other compression algorithms.

You can extract tar.bz2 files using tar command which is included by default in all major Linux distribtions.;

The following example will extract the file to your current directory;

tar xf /path/to/filename.tar.bz2

To extract the file to other directory, use the -C option as the following;

tar xjf /path/to/filename.tar.bz2 -C /path/to/target

Certain SSH server is configured to not allow root login mainly due to security and audit reason. You can disallow root login to your server with these simple steps;

1. Set PermitRootLogin to no in /etc/ssh/sshd_config

   PasswordAuthentication no

2. Reload or restart SSH

   How to restart SSH service

PNG or Portable Network Graphics is a file format for image that employs lossless data compression. It is meant to replace patent encumbered GIF file format, hence the acronym itself is optionally recursive, which unofficially stands for PNG’s Not Gif.

Employing a lossless data compression, PNG’s images while being sharp can sometimes relatively be big in size. To keep the file size small while maintaining the sharpness of the image, there is a tool available that can further compress a PNG image, losslessly.

The command line based program is called Pngcrush, and is available for both Windows and Linux. The program can reduce the file size for up to 40% less from the original by trying various compression levels of PNG filter methods.

Running the program is as simple as supplying the input and output file, as in the following example;

$ pngcrush  input.png output.png

 | pngcrush 1.6.6
 |    Copyright (C) 1998-2002,2006-2008 Glenn Randers-Pehrson
 |    Copyright (C) 2005      Greg Roelofs
 | This is a free, open-source program.  Permission is irrevocably
 | granted to everyone to use this version of pngcrush without
 | payment of any fee.
 | Executable name is pngcrush
 | It was built with libpng version 1.2.27, and is
 | running with  libpng version 1.2.27 - April 29, 2008

 |    Copyright (C) 1998-2004,2006-2008 Glenn Randers-Pehrson,
 |    Copyright (C) 1996, 1997 Andreas Dilger,
 |    Copyright (C) 1995, Guy Eric Schalnat, Group 42 Inc.,
 | and zlib version 1.2.3.3, Copyright (C) 1998-2002 (or later),
 |    Jean-loup Gailly and Mark Adler.
 | It was compiled with gcc version 4.3.1 and gas version 2.18.50.20080610.

   Recompressing input.png
   Total length of data found in IDAT chunks    =    90188
unknown chunk handling done.
   IDAT length with method   1 (fm 0 zl 4 zs 0) =    94524
   IDAT length with method   2 (fm 1 zl 4 zs 0) =    94871
   IDAT length with method   3 (fm 5 zl 4 zs 1) =    93666
   IDAT length with method   9 (fm 5 zl 2 zs 2) =   181820
   IDAT length with method  10 (fm 5 zl 9 zs 1) =    88388
   Best pngcrush method = 10 (fm 5 zl 9 zs 1) for output.png
     (2.00% IDAT reduction)
     (2.14% filesize reduction)

   CPU time used = 0.510 seconds (decoding 0.060,
          encoding 0.450, other 0.000 seconds)

Pngcrush can also run in batch mode, where running the following command will compress all the PNG files in the current folder, and save it to a folder named compressed, adding the suffix -compr to the file name.

$ pngcrush -d compressed -e -compr.png *.png

Kubuntu and any KDE based distribution in general uses system title bar for Chromium by default. It seems redundant and take up precious screen real estate.

It can be disabled with these simple steps;

1. Open Settings by selecting Settings from the hamburger menu on the top right of Chromium window.
   
2. Search for Use system title bar and borders in the Appearance section.
   
3. Toggle the option and you’re done.
   

DokuWiki by default returns 200 HTTP status code for non-existing pages. This might trigger duplicate content alert to search engines and would somehow affect the site’s SEO. There’s an option to still give the nice DokuWiki Not found page yet still returning the 200 HTTP code.

Pointing your browser to the root directory of your Symfony project will bring you to the module default of the first app you created for the project. The following is the content of the file web/index.php in your Symfony’s project folder;

<?php


require_once(dirname(__FILE__).'/../config/ProjectConfiguration.class.php');

$configuration = ProjectConfiguration::getApplicationConfiguration('admin', 'prod', false);
sfContext::createInstance($configuration)->dispatch();

In the example, the default app is admin. To make it load the app frontend for example, just replace admin in the file with frontend, and you’re all set.

You can easily create an SSH key pair by using ssh-keygen as in the following example.

$ ssh-keygen 
Generating public/private rsa key pair.
Enter file in which to save the key (/home/user/.ssh/id_rsa): 
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/user/.ssh/id_rsa.
Your public key has been saved in /home/user/.ssh/id_rsa.pub.
The key fingerprint is:
1a:6c:a4:94:df:e0:19:ec:85:b0:3f:27:e4:a1:de:65 user@host
The key's randomart image is:
+--[ RSA 2048]----+
|                 |
|   .             |
|    o E          |
|     O o         |
|    c @ S        |
|   o A @         |
|    . E .        |
|   . =           |
|    .            |
+-----------------+

There are a few things that you might want need to take note;

1. A 2048 bit RSA key pair will be generated by default. You can use different key type by using -t option and specify any of the supported key types

   dsa ecdsa ed25519 rsa rsa1

2. The private key will be stored in ~/.ssh/id_rsa while the public key will be stored in ~/.ssh/id_rsa.pub. You can specify other location when prompted during the key generation process if you already have a key pair at the default location
3. You can specify passphrase for your key pair when prompted but you’ll have to not set the passphrase to use passwordless SSH login

   How to configure passwordless SSH login

   How to add or remove passphrase on SSH key