Deathwing00's Space WebLog of Ioannis Aslanidis (aka Deathwing Zero Zero)

28Jul/100

GUADEC streamed live in WebM using Flumotion

GUADEC (GNOME Users’ And Developers’ European Conference) of this year, 2010, is being streamed live from several locations (Paris, Copenhagen and Seville) in WebM format using Flumotion and the Flumotion Streaming Platform.

It is amazing to be able to finally start streaming in an open format, no more flash! Remember that you need Firefox 4 or Opera 10.60.

You can find more details about the event and about the streaming here.

You can use the following URLs to watch it live:

Enjoy the live streaming!!!

5May/105

Finally a graphics card for Linux that works flawlessly with compiz and is lightning fast

After years of struggling and looking around, I have finally found a graphics card that works flawlessly when running compiz under Linux and that processes all the effects at lightning speed. I've never seen something like this for that reasonable price!

29Apr/102

Testing out Funtoo

The other day I decided to give a try at Funtoo (for those that do not know it yet, a variant of Gentoo). I am very impressed with the improvements that Daniel Robbins has done so far.

Among the things that I like:

23Mar/100

How to be able to use your ssh agent forwarding after using sudo

Recently we have hit with a solution for an issue where we wanted our users to run certain secure commands as root, which included repository commits. This can easily happen to you if you use savon, for instance.

Because of the nature of savon, given that it understands not only about standard permissions and modes, but also of SELinux contexts, this tool can only be used properly as root, if you want to use all of its features.

The problem comes when you need non-root users, that work with certain files in a directory, to be able to commit these changes. You have to use sudo, which you surely already know. For increased security, standard distributions drop most environment variables when you run a command with sudo.

20Mar/107

Check that a physical link is up with the proper speed

This check is great to detect when a network cable for whatever reason deteriorates and stops providing the desired up-link speed. It works perfectly for any system that has ethtool installed.

This particular check has helped me as a sysadmin to detect bad quality cables that, after being reused many times, end up deteriorating and do not let me get 1Gbps in RJ-45 CAT 5E cables. I have also been able to detect network card failures, and also malfunctioning switch ports.

7Mar/100

Check that an FTP account is fully working

This script uses lftp, a sophisticated ftp/http client, to check not only that a give FTP account is accessible, but that it is also able to list files and directories, to get and put files and to delete files. This simple script is fast, easy to configure, flexible and can be extended easily.

Sometimes, things like SELinux, a failed network mount point or wrong permissions cause an FTP account to not work properly. With this check, you will be able to detect it immediately.

2Mar/100

Puppetcamp Europe 2010

According to this information, Reductive Labs, the team behind puppet, has announced that Puppetcamp Europe 2010 will happen on 27 and 28 May 2010 in Ghent, Belgium. For those who do not know, Puppet is an open source application for system control automation.

25Feb/100

Releasing cached memory in Linux

Under normal circumstances, modern Linux systems try to cache into memory disk data that is accessed often. Sometimes, we have that much memory in the system that our kernel keeps filling up the memory by caching every piece of data we access.

Other times, because of the swappiness factor, active data finds its way into the swap instead of the main memory. I have seen this behavior in a few systems hosting databases, specially running mysql, and it is a serious performance hazard.

In order to fix systems like this, we need to fix the swappiness, drop the caches and, swapoff and swapon the system swap.

17Feb/100

Check that a glusterfs partition is mounted

When using glusterfs in a production system, it is mandatory to properly monitor that the partition is mounted and performing well, specially in heavy loaded environments.

I have created a nagios plugin in bash that monitors a glusterfs mounted partition and detects whether the partition gets unmounted, responds slowly or gets disconnected from the server (causing reading processes to die in an uninterruptible sleep state, which will force you to restart the system in order to get rid of them).

17Feb/100

Check the percentage of CPU consumed by processes with the same name during a certain interval

Many nagios scripts use ps to compute the percentage of CPU consumed by a process. Although at first instance this might seem a good approach, if you read properly the documentation, you will notice this:

CPU usage is currently expressed as the percentage of time spent running during the entire lifetime of a process. This is not ideal, and it does not conform to the standards that ps otherwise conforms to. CPU usage is unlikely to add up to exactly 100%.

This means that ps is useless if you require to know whether a certain process is consuming a lot of CPU percentage during a given interval. For instance, imagine that you want to detect whether a given process has hanged and is consuming lots of CPU; using ps you will be completely unable to detect it.

In order to work around this and provide a proper monitoring solution for this type of problem, I have written a script in python that calls top. This command does offer the percentage of CPU during a given interval, not for the whole lifetime of the process.