(bash): The most useless commands (11)

After talking about
  1. rev
  2. yes
  3. sl
  4. cowsay
  5. cmatrix
  6. cal
  7. rig 
  8. pi
  9. figlet
here a packages called filters which comes with such commands:

$ echo hello my friend | jethro
hello mah friend
$ echo hello my friend | chef
hellu my freeund
$ echo hello my friend | kraut
hello mein friend
       All  of  these  programs are filters to do all sorts of strange things to text.  No personal, racial,

WLAN management with linux: networkmanager CLI "nmcli"

Configuring WLAN settings with the graphical user interface network manager is really easy.
Nevertheless sometimes it is necessary to configure the WLAN settings via a terminal. And therefore you should use nmcli:

To get a list of all available networks use "nmcli d wifi list"
$ nmcli d wifi list
*  Gastzugang           Infra  12    54 Mbit/s  72      ▂▄▆_  WPA2      
   Napoleon Gastzugang  Infra  36    54 Mbit/s  27      (more...)

Bash: enabling Eclipse for Bash Programming | Plugin basheclipse (debugging) part 2

If you want to debug bash scripts inside eclipse you have to do 2 things:
As i wrote in the last posting, toggling breakpoints was neither possible in Eclipse Neon  nor Eclipse Juno.

First you have to install JDK 1.6 and Eclipse Luna to be able to set breakpoints. (see EDIT at the end of (more...)

(bash): The most useless commands(10)

After talking about
  1. rev
  2. yes
  3. sl
  4. cowsay
  5. cmatrix
  6. cal
  7. rig 
  8. pi
here another pretty useless command:
~$ figlet apt-get update
             _                   _                     _       _      
  __ _ _ __ | |_       __ _  ___| |_   _   _ _ __   __| | __ _| |_ ___
 / _` | '_ \| __|____ / _` |/ _ \ __| | | | | '_ \ / _` |/ _` | __/ _ \
| (_| | (more...)

Customizing a CoreOS image/iso: Ignition

After the first steps with coreos (virtualbox installation) and a successful ssh login, it is clear, that the coreos image has to be customized. If not, every reboot will clean up every configuration provided after reboot.

CoreOS provides a coreos-install script to do this.
coreos-install -help
Usage: ./coreos-install [-C channel] -d /dev/device
    -d DEVICE   Install Container Linux to the given device.
    -V VERSION  Version to install (e.g. current) (more...)

CoreOS: structure of the ISO image

After some first steps with CoreOS ("First step to micorservices: CoreOS on virtualbox") my problem is, how to customize CoreOS. After each reboot all changes are gone (tmpfs / squashfs).

There are some tutorials which recommend the usage of etcd, but even this has to be configured into the CoreOS linux...

The first idea: what about customizing the ISO image...

mount -o loop coreos_production_iso_image.iso /media/iso
Inside this:
$ ls
coreos  isolinux  syslinux

CoreOS: How to login via ssh (default password?!)

After the installation of a coreos you want to login via ssh (because of wrong localization inside your virtualbox/vmware console and no client tools installed (copy/paste not working, etc...)?
If you ask your preferred search engine, you will get many answers that there is not default password...
(Of course! The idea behind containers and container schedulers is, that everything works automatically and typing passwords does not fit in this mantra).

But no worries, only (more...)

Linux Containers – Container LInux: Core OS – a minimal linux? A quick overview: diskspace, mounts, commands, kernel, …

Virtualization techniques can be grouped into two categories
  1. os virtualization like VMware, Virtualbox, etc.
  2. container virtualization like Docker, etc.

Everybody is familiar with the first category. Creation of virtual machines is well known and most of us have created already tens or hundreds of such machines. (and deleted and lost them after some weeks). One of the benefits is, that it is easy to run additional machines on our laptops / workstations.
The second category (more...)

First step to micorservices: CoreOS on virtualbox (1)

I read some articles about microservice architecture and about kubernetes / apache mesos.
My conclusion from these articles is, that lightweigt servers are a key point to this microservice architecture. Just to learn how tiny such a OS could be, i will try to install CoreOS inside virtualbox.

There is an easy way to get CoreOS running ("booting CoreOS container linux from ISO"), but there some limitations stated on the CoreOS website:

  1. There (more...)

(bash): The most useless commands (9)

After talking about
  1. rev
  2. yes
  3. sl
  4. cowsay
  5. cmatrix
  6. cal
  7. rig
here another pretty useless command:

$ pi 10
       The  pi  command  prints  100 decimal digits of Archimedes' constant pi or a number of
       digits specified by an integer parameter on the command line.

Ingress: Level 16 reached…

After long time playing google/niantic's ingress (the predecessor of pokemon go - all the arenas are portals in ingress, most of them created by ingress players) i reached the last level:

And the usual welcome package:

I am wondering, wether i should continue playing or quit the game for now or ever.
Perhaps reading this discussion (What do lvl 16 players play for?) may help me.

(bash): The most useless commands (8)

After talking about

  1. rev
  2. yes
  3. sl
  4. cowsay
  5. cmatrix
  6. cal
 i found another funny command:
Its manpage tells the following:
       Rig  is a utility that will piece together a random first name, last name, street num‐
       ber and address, along with a geographically consistant (ie, they all match  the  same
       area) city, state, ZIP code, and area code.

       It is suitable for such applications as feeding the NY times registration (more...)

OpenJDK 9: Jshell – Using Swing / doing GUI stuff

After the buitin commands of jshell and how to load and save scripts i tried to get swing components running.

I created a script  HelloWorld.java
import javax.swing.*;       

JFrame frame = new JFrame("HelloWorldSwing");
JLabel label = new JLabel("Hello World");
But this does not work with Ubuntu:
jshell HelloWorld.java
# A fatal error has been detected by the Java Runtime Environment:

Bash: enabling Eclipse for Bash Programming | Plugin basheclipse (debugging) part 1

In my last posting i showed how to install the plugin shelled and its configuration options.

Now the next step is to install basheclipse, which enables eclipse in conjunction with shelled to debug bash scripts.

Step 1: Download basheclipse

Step 2: Do not copy the jar file to the plugins directory if you are using Eclipse Neon. Copy them to the dropins directory.

Step 3: Restart eclipse (and wait. I had to wait nearly 5 (more...)

OpenJDK 9: Jshell – how to load scripts and how to save/persist finished snippets

In my last posting i showed the builtin jshell commands and how to start working with the java shell.

What about loading and saving scripts?

I created a file myshell.txt with this content:
class MyClass {
 private int a;
 public MyClass(){a=0;}
 int getA() {return a;};
 void setA(int var) {a=var; return;}
MyClass ZZ;
ZZ = new MyClass();
The help shows the following:
-> /help /open

|  /open

|  Open a (more...)

OpenJDK 9: JShell – an interactive java interpreter shell | builtin commands

One of the new features of java 9 is jshell (JEP 222).

On my ubuntu system the installation was quite easy:
# apt-get install openjdk-9-jdk-headless
and you can find
$ ls /usr/lib/jvm/java-9-openjdk-amd64/bin/
idlj       jcmd    jmap        jstatd       schemagen
jar        jdb     jmod        keytool      serialver
jarsigner  jdeps   jps         orbd         servertool
java       jhsdb   jrunscript  pack200      tnameserv
javac      jimage  jsadebugd   policytool   unpack200
javadoc    jinfo   jshell      rmic         wsgen
javah      jjs     jstack      rmid         wsimport
javap      jlink   jstat       rmiregistry  xjc
 (in the third (more...)

Bash: enabling Eclipse for Bash Programming | Plugin Shelled (shell editor)

After writing several posts about useless shell commands i tried to enable Eclipse for working with the bourne again shell.

First step is to get a plugin for syntax highlighting. The plugin shelled
is very easy to find. Just download the zip

and in Eclipse go to "help --> install new software".
There you have to add the archive:
And all other clicks are straight forward:

After the installation of the plugin you (more...)

(bash): The most useless commands (7)

After talking about
  1. rev
  2. sl
  3. cowsay
  4. cmatrix
here another pretty useless command:
Today with every smartphone having its own calendar app or every e-mail program with integrated time planning function this command is no more needed. The manpage says:
     cal, ncal — displays a calendar and the date of Easter
And here we go:
$ cal 2000

(bash): The most useless commands (6)

After talking about
  1. rev
  2. sl
  3. cowsay
 i found another funny command:
The manpage says:
       CMatrix - simulates the display from "The Matrix"
and it is true:

(bash): The most useless commands (5)

In a comment Albert Godfrind pointed out, that the commands i was talking about like
  1. rev
  2. sl
  3. cowsay
are not really bash commands (in a way that they will be installed within the installation of the bash shell). They are commands, which can be used from on every shell. So my headline is a little bit missleading - thanks for this notice.

Just for clarification here a list with all bash builtin commands: