Category Archives: Linux

NVidia driver fails to initialize after X restart

This is mainly a note to myself. Sometimes when the X server is restart it complains that nvidia driver couldn’t be initialized and that no screens were found. This may be a result of a version mismatch between X11’s and the kernel’s nvidia module. The solution is to

modprobe -r nvidia

before restarting the X server.

Blocking IP Range using UFW

Uncomplicated Firewall (ufw) is one of the greatest frontends to IPTables I’ve encountered. It is very simple to use and I just wish it was also available for Gentoo. Up until recently everything went smoothly for me and ufw, but we hit some rough waters when I’ve tried to block an IP range.

To block an IP or IP range in ufw you should do

sudo ufw deny from 188.162.67.197/21

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Using Amarok Generated Playlists (m3u) on Sansa Clip

Few days ago, for the first time, I’ve created a playlist using Amarok for files on my Sansa Clip player. To my surprise (and disappointment) when I’ve unplugged my Sansa Clip and powered it, the playlist showed up empty, unlike playlists which originated in Windows. As I keep my music collection organized in Amarok, the situation seemed to be very uncomfortable.

I’ve decided to compare one of the working playlist files and the “empty” Amarok generated playlist. Two things were noticeable:

  1. Amarok uses forward slashes, like in a Linux environment, and the working playlist used backward slashes.
  2. The working playlist used relative paths without any prefix – directly beginning with the path. Amarok prefixed the relative paths with a dot-slash (./).

After noticing those things I’ve modified my Amarok generated playlist to look like the Windows generated one, and voila, it worked. I tried going through Amarok’s configuration dialogs to find some option controlling the format of generated m3u playlists, but couldn’t find any (I’m using Amarok 1.4.10). So with my newly found wits I’ve looked for a way to make using the playlists easier. I’ve came up with the following one-liner:

find -name "*.m3u" | xargs -I{} sed "s/^\.\///;s/\//\\\\/g" -i'' {}

The command should be run in the MUSIC directory of the Sansa Clip’s filesystem. It recursivey looks for m3u playlists and for each one strips any leading dot-slash and replaces forward slashes with backward ones. It can be used to easily convert all your playlists to the format understandable by Sansa Clip.

Upgrading All KDE Related Packages in Gentoo

Yesterday, Gentoo marked KDE 3.5.10 as stable on amd64. I looked for a way to upgrade all of the KDE related packages, without manually specifying each one of them. Normally one could do

emerge -avu world

but I encountered some nasty conflicts that I didn’t have time, nor will, to resolve at that time. So I’ve looked for a different solution. To my rescue came qlist for the great app-portage/portage-utils package. This package provides a set of very fast utilities to query portage. I’ve used qlist to list all of my installed packages, grep‘ed the list and piped the result as arguments to emerge using xargs.
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Installing Lighttpd-1.4.22 on Ubuntu 8.04

I had some problems with the lighttpd-1.4.19 that comes with Ubuntu 8.04, mainly it’s problems of handling the HTTP header Expect: 100-continue (which older versions of Lighttpd return error 417). The problem was fixed in Lighttpd-1.4.21, but 1.4.22 is the newest version so I’ve decided to install it.

As I mentioned before, Ubuntu doesn’t have lighttpd-1.4.22 for 8.04, and it’s also not available in the updates or backports repositories. Fortunately, I’ve found that the package is available from Debuian Sid (unstable). Here are some instructions on how to install it.
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Iptables Cheatsheet

From time to time I find myself having to go through man pages and googling for some simple iptable rules. This post is meant as a cheatsheet for me, so I can concentrate here various rules and remarks.

I hope others will benefit from this cheatsheet as well. Intend to expand it over time as I gather more rules and tips, so bookmarking the post might be a good idea. Last but not least, if you have some useful iptables rules I’ve missed please send them using the comments.
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Starting tracd without Root Privileges at Startup

I use Trac for the Open Yahtzee website. I’ve decided to use tracd for serving the requests (due to a configuration issue I didn’t want to mess with), which required starting it each time the server restarts. I’ve already written one solution for it, in the form of an init.d script for tracd. However, it bothered me that the tracd runs with root privileges which it doesn’t really requires.

After searching a bit I’ve found out that cron can run tasks on startup using the special @reboot keyword instead of the normal time fields. So edit your crontab and add the following line:

@reboot /usr/bin/tracd --daemonize --pidfile=~/run/tracd.pid --port=PORT --hostname=HOSTNAME -s TRAC_ENV

Just replace PORT, HOSTNAME and TRAC_ENV with the appropriate values for your environment, and make sure you got a run/ sub-directory in your home folder (or change the pidfile value).

To stop the server just do:

kill `cat ~/run/tracd.pid`

While there is no straight way to restart the server (like /etc/init.d/tracd restart), it’s a good compromise for dropping root privileges.

Amarok Sleep – Stop Playback After Specified Amount of Time

Amarok is my favourite music player. I like to listen to music when I go a sleep, but I don’t want the music to keep playing all night long. This is why I’ve added a sleep feature to radio.py. Unfortunately Amarok doesn’t have a built-in sleep functionality, but the Amarok developers left open door for us to implement it with ease by means of interfaces allowing to control amarok from the command line.
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phpMyAdmin + Lighttpd in Gentoo

Usually installing software in Gentoo is a piece of cake. Just emerge what you want and (with the right USE flags) and everything will be ready for you. However, as today I’ve found out today, installing phpMyAdmin with Lighttpd isn’t trivial as it should be.

In this post I’ll try to walk you through the necessary steps to install phpMyAdmin with Lighttpd in Gentoo.
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