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How to find your IPv4 and IPv6 ip-addresses?

December 7th, 2018

How to check your IPv4 and IPv6 ip-adresses on the command line

Sure you can start up your browser and use Google to find a suitable website, but why not keep it simple and use the command line for this trivial task. Fire up a terminal and type:

> my_ip
> 2001:db8:85a3::8a2e:370:7334

Above IP-addresses are bogus, but you got my drift. To do this simply create the following bash script:

# bin/my_ip

curl -6
curl -4

It will first output your IPv6 address.  If you don’t have one, it it will tell you:

> curl: (7) Couldn't connect to server

The script uses the great curl application with the simple -6 and -4 flags, to connect with IPv6 and IPv4.

Of course you could extend the script a bit to include geographical information:
# bin/my_ip

curl -6
curl -6
curl -6
curl -4
curl -4
curl -4

Now you will get info about your city and country as well.
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How to Make the Music Player Daemon (MPD) Autoplay on a Raspberry Pi

November 13th, 2018

Music Player Daemon (MPD) is a terrific open source music player and maintains a good organized library of your music in an efficient database. MPD is a server so you need a client. That can be your laptop, to your phone, your browser, your whatever, or you can run a client on your Rpi locally (mpc). Or all together.

It does run fine on the cheapest raspberry pi, so your ready to go for 5 euro. The Pi only has a high quality HDMI output, for older Hifi systems with analogue connections  you need something like the HifiBerry.

MPD uses much less CPU then running Kodi, 4% instead of 40% on the original Raspberry Pi.

Furthermore you can put your music on an external USB stick or  NAS with Linux NFS or the slightly inferior Microsoft Windows Samba shares.

If you haven’t installed MPC yet, do that first:

sudo apt install mpc

Normally MPD will resume play after shutting down, but to make MPD auto-play always simply add this to your systemd.service  file:

ExecStartPost=/usr/bin/mpc play

How to do that? Just edit the file:

sudo vi  /etc/systemd/system/

And add it under the line starting with `ExecStart`

ExecStart=/usr/bin/mpd --no-daemon $MPDCONF
ExecStartPost=/usr/bin/mpc play

Save it, stop MPD, and reboot your pi. And the music will play 😉

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Using Krusader with Ubuntu 18.04

June 7th, 2018

Krusader is a very fine two pane file-manager that comes with many powerful inbuild features, while Nautilus or the Mate fork (Caja) lack many of those important features: two panes, open folder in terminal (with keyboard shortcut), a useful bookmark manager, password manager (for remote sites like (S)FTP, configurable user-actions, and its highly configurable (with a lot of keyboard shortcuts).

Once you’ve experienced Krusader from the keyboard, Caja or Nautilus is simply inferior in daily usage. It seems that Gnome’s choice to embrace touch screen devices comes with a cost for heavy keyboard desktop users.

This doesn’t mean I don’t use Nautilus, I do! I simply use both file managers. Remember, everything is a file in the Unix philosophy. So the file-manager, next to the editor, is the most important tool in Linux.

Browsing two panes in Krusader is easy, searching, copying, moving files, or synchronizing panes, browsing archives, it’s all supported, with nice keyboard support.

Some of Krusader’s powerful features:

  • remote mounts (SFTP/SSH/FTP)
  • compare by content
  • batch multi rename
  • synchronize panes
  • split/ combine files
  • verify files checksum
  • visual tool to show folder usage/size
  • user-actions to easily setup  cli based actions for selected files, like resizing images, converting media-files etc, all with keyboard shortcut support.
  • mirror mode, traversing trees

Krusader does need some additional tools to show real power, like krename, kate (for internal viewer), and the some icons are missing with a default install in Ubuntu 18.04. We will fix that.

Start with installing Krusader:

sudo apt install krusader

# and some tools
# krename powerfull batch rename tool)
# kate (editor)
# bookmark manager
sudo apt install keditbookmarks
# saving passwords
sudo apt install kwalletmanager
# PGP encryption for kwallet
sudo apt install kpgp
# support for (s)ftp mounts
sudo apt install kio-extras
# kde terminal, not needed if you tweak the Krusader settings to use gnome-terminal or mate-terminal
sudo apt install konsole
# for visual diff and merge tool
sudo apt install kompare
sudo apt install meld

Now you could start-up Krusader, it will ask you about some path for tools for packing and unpacking, you can install them later if you need them (rar/unrar etc).

Now you will probably notice, Krusader looks weird, it’s missing icons. By default Krusader is using breeze-icons. Unfortunately installing the breeze deb package will not do the trick. It’s a long story how to fix that, but the easiest method I came along was this:

Extract the binary icon-theme from the icon-package (breeze-icon-theme-rcc_5.46.0-1_all.deb), rename it  and place it in the Krusader config folder.

Download the deb, and open the deb with your archive manager and extra this file /usr/share/icons/breeze/breeze-icons.rcc.

Rename and copy it to the Krusader config map:


Restart Krusader, and icons are in place.

If you want  Krusader to  save passwords: Setup a new wallet with kwalletmanager, and Krusader will use that default wallet. Probably you will need a logout/reboot.

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Security by design: following the right principle

April 6th, 2018

Since there was some attention to a CSS driven keylogger, it’s good again to point out the security risks of third party content. That risk is huge.

When a third party CSS Stylesheet can steal your password, it would be a piece of cake for any Javascript script to do the same.

If you follow this blog, it will not surprise you that we’re skeptical to all the JavaScript driven frameworks that are fashionable. In general Javascript is bad for security, privacy, and the planet 🙂 : battery usage. It’s good for tracking, fingerprinting and advertisements, and visual eye-candy.

Yes, JavaScript can be nice, but please adhere to these old principles: graceful degradation and progressive enhancement. And it’s fashionable not to follow those principles.

Don’t force JavaScript, because you’re trying to sell adds, or track users.

Don’t overdo JavaScript: an URL with your contact info should have your contact info (in HTML). Otherwise you should point to another URL. Don’t hide this information behind Javascript and in JSON somewhere. You’re breaking the internet. Keep information accessible.

It’s important to underline again. Every script that is loaded with <script> has access to the DOM, and if the page is a login page, it has access to the password and username.

So a simple principle can be deducted, and it’s a shame that we have to repeat it here.

Never add any (third party) script to a login page. NEVER.

Nobody should be authorized to have access to a plain password, except for the user. Nobody. Limit access by design, not by trust.

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How to run or boot Raspbian on a Raspberry Pi Zero without an SD-card.

March 22nd, 2018

In an earlier post I explained how you can run and connect to a Raspberry Pi Zero with just an USB cable. Still the RPI Zero was using a micro SD card.

Luckily the great minds of the Raspberry Pi Foundation developed new boot modes: ethernet boot and USB Mass Storage Device (MSD) boot for the Raspberry Pi 3.

Now they came up with USBBoot, a tiny program that pushes the bootcode over the USB to the Raspberry Pi Zero (Raspberry Pi model A, Compute Module, Compute module 3 and Raspberry Pi Zero and Raspberry Pi Zero W), so it can boot without a micro SD-card.

Boot a RPI Zero from your laptop without SD card

In this post we will boot the Zero with the latest Raspbian Stretch (lite) from an common Ubuntu laptop, running 16.04LTS. It is surprisingly comfortable once you’ve set it up. And remember we’re running the Zero without any SD card, which costs are higher then a Raspberry Pi Zero. You do not need an SD card at all.

Yes, we use a standard USB cable to power,  connect, provide internet-access, an OS and storage for the Pi Zero.

So we gonna run the poor Raspberry Pi headless (=no monitor), armless (=no keyboard or mouse) and brainless (=no memorycard). And you know what? Back to the basics make the little gem shine!!

Read the rest of this entry »

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How to load an image in HTML/CSS

March 6th, 2018

Using an IMG tag

<img src="path/to/image.jpg" alt="">

Setting a background

<div style="background-image:url(path/to/image.jpg)" ></div>

Using the picture tag

<picture> <source srcset="path/to/mage.webp" type="image/webp" > <img src="path/to/image.jpg" alt=""> </picture>

This will load a webp format in browser that suppport it, and a jpg image as fallback. Webp is a format that offer better compression than jpg combined with transparancy. Unfortunately it is not supported yet by Firefox or Safari.

An IMG tag is needed, the picture tag will not show anything, it will just let you set several `url` choices for image type or media selector.

Setting the background in a pseudo-element

 background-image: url(path/to/image.jpg);

Using an IMAGE tag

<image src="path/to/image.jpg" alt="">

Yes, you can use an image tag as well, this will be interpreted as `img` tag in the DOM.

Using the picture tag with an image tag

 <source srcset="path/to/mage.webp" type="image/webp" >
 <image src="path/to/image.jpg" alt="">

Setting the content in a pseudo-element

 content: url(path/to/image.jpg);

Yes, you can load in image in HTML by setting to content property to an URL.