Category Archives: Linux

Stuff about Linux

Linux: Use X11 forwarding with putty and su/sudo


when you use X11 forwarding with PuTTY or ssh -X a TCP Socket is opened to which each user can connect. The connection to the X11 itself is protected by an authentification cookie.

Means when you add this cookie to the session launched by su you could use X11 forwarding.

An example. Connect to a linux machine as user michael (by putty or from another linux machine)

michael@debdev ~ # ssh -X michael@debdev1 

In the session of debdev1 list all xauth cookies.

michael@debdev1 ~ # xauth list
debdev1/unix:10  MIT-MAGIC-COOKIE-1  7ea68cc88e74c1697aa6c757504fc0d7 

Note: these cookies are stored the users home directory in file .Xauthority => ~/.Xauthority

Then switch to another user on this machine

michael@debdev1 ~ # sudo su helena

When you try to start a X11 client you got some errors like this

helena@debdev1 ~ # xterm
Can't connect to X11 window server using 'localhost:10.0' as the value of the DISPLAY variable.

Then verify you already have a ~/.Xauthority file

helena@debdev1 ~ # ls -l ~/.Xauthority

If not create a new file

helena@debdev1 ~ # touch ~/.Xauthority

and add the authentification cookie

helena@debdev1 ~ # xauth add debdev1/unix:10  MIT-MAGIC-COOKIE-1  7ea68cc88e74c1697aa6c757504fc0d7

Then you should be able to start X11 programs


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Linux: Call a phone and play a message with asterisk


asterisk is a complete VoIP/SIP solution but can also be used as a SIP client to send a prerecorded message. In this example I will use a Fritz!box as the upstream SIP Server for asterisk.
Continue reading Linux: Call a phone and play a message with asterisk

Youtube: Save the audio stream of a youtube video as mp3


there is a python module if you want to save an audio stream of a youtube. youtube-dl is the choice for such tasks.
Continue reading Youtube: Save the audio stream of a youtube video as mp3

Linux: ip command line examples


the old style ifconfig, route and netstat commands does not support all network, especially IPv6, features shipped with modern linux distributions.

Replacement are ip (ifconfig, route) and ss (netstat). Here are some examples.
Continue reading Linux: ip command line examples

Linux: Change working directory to script directory in bash


short post. You start a bash script and want to change the working directory to the directory where the script is stored

Use this:

cd "$(dirname "$0")"