One-way email address

Tired of having to tell your email address every time you register for something on the net? http://wasteland.rfc822.org/faq.html provides receive-only email addresses which direct the incoming emails directly to a virtual trash can.

Password free SSH connection

Of course, using ssh without giving a password each time one logs in to the server heavily affects the security of the whole process. Using keys on both the client and the server machine gives third parties the possibility to copy the client key and be able to log in to the server. While this can be bypassed by specifiying the ip addresses with access to the server, hacking the client machine and logging in to the server from there is still possible. However, in some cases a password free ssh connection is preferable. Therefore, one has to create a public key, which will be given to the server machine, and private one kept on the client machine. The following procedure creates theese keys:

On the client machine, type

$ ssh-keygen -t rsa -b 1024

Enter the path where to save the key, e.g.

$ .ssh/ida_rsa

Leave the password blank.

Now, copy the file ida_rsa.pub to the server and add it to the file ~./.ssh/authorized_keys:

$ ssh-copy-id -i ~/.ssh/id_rsa.pub user@remote-system

Now

$ ssh user@remote-system

establishes the ssh connection without asking for a password anymore.

Evolution crashes and can not be restarted

Switching between categories of contacts leads to a crash of my evolution (2.12.0 on Suse 10.3). Afterwards, it isn’t even possible to restart it. At least the restart problem can be resolved by running

$ /usr/bin/evolution – -force-shutdown

in the shell.

(see original bug report)

Assinging variables via commands in a cshell skript

It is more or less well known that the ouput of a shell command can be redirected to a file via “>”. To assign a variable with the value of the command output, one has to use the quotes ` ` instead of ” ” or ‘ ‘ . For example,

$ set var = ` cat * | grep “text” | cut -d . -f1`

leads to evaluation of the command and assigning the result to the value of the variable var. This makes sense in all cases where the result of the command should not only be stored but is used in further commands.

People who don’t know nothing about the laws of physics

Standing in the queue of the supermarket, I often undergo the following scenario: The person in front of me just wants to buy some bottles of wine and nothing else. So here is the question: Why is it so difficult to put theese bottles in a way that they are aligned with the direction of motion of the conveyor belt which would prevent them from moving and colliding with each other all the time? Some people lay them down perpendicularly to the conveyor belt, some even place them upstanding and do not even seem to recognize that inertia is a phenomenom not beeing restricted to the outside world of the supermarket. One should place signs at the cash desks saying “Be aware of physics!”

gcc options

Use -g to generate debugging information when compiling the source code. This information will be stored in the object file. It describes the type of data of the variables and functions and the correspondence between source line numbers and addresses in the executable code.

I currently start to use the DDD debugger. The manual can be found here.

sshfs

One of the most useful information I got during the last weeks is to use sshfs. Thanks liquidat for the short tip. sshfs serves to mount a directory on a different computer via ssh. This simplifies my work on the Supercomputer HLRB II (SGI Altix 4700) of the Leibniz-Rechnezentrum Muenchen a lot as I can directly use the analysing software of my own computer or easily compare to older data stored on my local machine.

Linux is not Windows

As a relatively new Linux user, I found this article very interesting: http://linux.wordpress.com/linux-is-not-windows/

Meine Diplomarbeit als pdf

diplomarbeit.pdf