Archive for the ‘operating_systems’ Category

Quick overview over nearby wireless lan hotspots

Thursday, March 6th, 2014

Here is a useful little command to get a quick overview over nearby hotspots:

 iw dev wlan0 scan  | grep 'SSID\|signal\|primary channel'
        SSID: 5g_station
                 * primary channel: 36
        signal: -42.00 dBm
        SSID: 2g_station
                 * primary channel: 6
        signal: -72.00 dBm

vimrc for latex

Wednesday, March 5th, 2014

Ah yes – finally – blog post time again :)

Since I am currently writing a lot of latex with vim I thought I backup share my ~/.gvimrc on my blog:

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:setlocal spell spelllang=en_us " enable spell checking (Ctrl x + s for suggestions)
:set wrap			" wrap too long lines
:set guioptions-=m 		" disable menu bar
:set guioptions-=T		" disable toolbar
:set spellfile=/path/to/spellfile-en.utf-8.add
:set colorcolumn=80		" show a red bar in column 80
:set textwidth=80		" automatically break after column 80
:set encoding=utf-8  		" The encoding displayed.
:set fileencoding=utf-8  	" The encoding written to file. Use file -bi  <file> to verify

Puppet

Tuesday, August 7th, 2012

I started to roll out puppet to manage our servers at work and have to say I am impressed. It really changed the way I think about managing systems and is so much cleaner and easier to understand than the ‘traditional’ way.
Just being able to automate often repeated steps like enabling LDAP access or distributing config files makes puppet worthwhile. That the configuration is self documenting and versioned makes puppet priceless.
I will not post a tutorial here, just links to a few I found useful:

If you have to manage more than two or three servers, read up on puppet and consider using it (or any other configuration management tool).  It will be worth the time learning it.

Connecting two monitor to a NVIDIA card without the proprietary driver

Sunday, November 16th, 2008

For a long time I searched for a way to connect two monitors to an NVIDIA graphic card without using the proprietary nvidia driver (mainly because I wanted to try use OpenBSD and 64bit FreeBSD).

Somehow I never read nv’s (the free Xorg driver) man page – until today. And there it is, clear as crystal:

Option "Dualhead" "boolean"
    Enables simple VBE-based dual head mode.  This sets the same resolution on both outputs and lays them out
    side-by-side.   The screens will be panned together as one big metamode if the virtual desktop is larger than both
    screens combined.

So I just had to change my Xorg config from:

Section "Device"
    Identifier     "Card0"
    Driver         "nvidia"
    Option        "TwinView"
EndSection

to

Section "Device"
    Identifier     "Card0"
    Driver "nv"
    Option	"Dualhead"
EndSection

So simple!

Ken Thompson on Security

Friday, July 11th, 2008

I just stumbled on a very good article by Ken Thompson on computer security:

Reflections on Trusting Trust

In this article Ken shows how easy it is to alter a compiler  to compromise all binaries created with it. Although 24 years old this article is a very interesting read.

us_de Keyboardlayout

Thursday, July 10th, 2008

The more I used it, the more unhappy I became with the us-intl keyboard layout. Especially all the dead keys (keys that may modify the following key e.g. ” + a to write ä) made typing tiresome. Always typing a space after double quotes is really not suited for programming.

I found a good tutorial on writing your own Xorg keyboard layouts:
Creating custom keyboard layouts for X11 using XKB

Using these instructions I created a us_de layout, that uses the us layout and bind alt + a/u/o/s to the german  umlauts ä/ü/ö/ß.

To install the file, just copy it to /etc/X11/xkb/symbols/ and edit your /etc/X11/xorg.conf (or type setxkbmap -layout us_de -variant basic into a shell): us_de

cups woes

Tuesday, March 4th, 2008

I just tried to get cups working and had the following problem:

I have a Lexmark Optra E+ parallel port printer and usually cups shows the parallel port as Device: on the second configuration screen. Only this time cups did not recognize the parallel port. lptest > /dev/lpt0 worked fine, just cups could not see the parallel port.

After about half an hour I finally found the solution:

# ls -l /dev/lpt0
crw——-  1 root  wheel    0,  57 Mar  4 20:00 /dev/lpt0

The rights on /dev/lpt0 were not set correctly. After changing them, everything worked fine:

# chmod 666 /dev/lpt0
# ls -l /dev/lpt0
crw-rw-rw-  1 root  wheel    0,  57 Mar  4 20:00 /dev/lpt0

Always compile audacious with dbus

Tuesday, March 4th, 2008

When I compiled audacious without dbus support yesterday I did not know it would break all application options (i.e. entering audacious -f on a shell skips to the next track) . Today I read a bit in the audacious sources and found that it has to be compiled with dbus support in order to work.

k3b on FreeBSD

Tuesday, March 4th, 2008

Today I configured k3b on FreeBSD. The building from ports works fine (although it took almost all morning. But then again k3b depends on most of KDE ;-)).

Turns out all I had to do was to enable the ATAPI/CAM Driver: link

Running ion3 on FreeBSD

Sunday, March 2nd, 2008

I just started to try out FreeBSD 7.0 (I am very impressed so far) and ran into huge problems installing my favorite window manager ion3 . Apparently the main developer had some trouble with various distribution maintainers and forbade then to ship ion (link).

After some try and error (and a pointer in the right direction by Markus) I finally figured out how to tweak the system.mk to make ion3 compile.

I had to change the following things:

  • install to $(HOME)/ion (you have to create this directory first)
  • comment DL_LIBS=-ldl (as this lib seems to be part of the FreeBSD libc anyway)
  • Set the path for lua 5.1
  • uncomment DEFINES =+ -DCF_NO_LOCALE -DCF_NO_GETTEXT

Attached: system.mk