Yenya's World

Wed, 18 Jul 2007

Single Point of Failure

Pavlína has discovered that our home computer cannot connect to the network. So I have tried to ping it from work, no response. Call to the hotline of our ISP: number is not available. Traceroute has ended somewhere in CESNET (our academic network). Even their web site was unreachable.

Netbox statistics

Netbox link to NIX.CZ.

Looking at the graph of their link to NIX.CZ revealed that there has been indeed some problem with their network for last two hours. Apparently even their call center is connected over their network via VoIP. Talk about single point of failure.

Section: /computers (RSS feed) | Permanent link | 6 writebacks

Mon, 16 Jul 2007

Referer Abuse

Well, not really abuse, but a clever hack of a HTTP Referer: header. While looking for information about new "polyinstantiated directories" feature I have found the namespace.conf(5) manpage on some web site.

The URL is, and it looks as an ordinary page. However, when you do a Google search for polyinstantiated directories and follow the link to namespace.conf(5) (today it was in the middle of the search results page), the searched keywords get highlighted. The highlighting is done by the Javascript at

This cool hack aside, the subject itself (polyinstantiated directories) is interesting on its own. It seems that the support for this has been in the kernel for a while (check whether your /proc/mounts is in fact a symlink to /proc/self/mounts), the user-space (Fedora rawhide) now supports it via the pam_namespace PAM module. Further reading on this topic include the SAGE-2006 talk by Russel Coker, and the Documentation/sharedsubtree.txt file from the kernel sources.

Section: /computers (RSS feed) | Permanent link | 0 writebacks

Thu, 12 Jul 2007

Dissecting a Hard Drive

In order to teach Iva something about computers (and, of course, out of my own curiosity), I brought a broken IBM 180 GB HDD home, and we have tried to dismantle it.

There was almost no surprise for me. The inner space of the drive was pretty simple and cleanly designed. Even the screws were almost uniform, with only two types of head used (Torx-10 and Torx-15). The interesting parts were the following:

Our future project is to get an older drive and compare how the technology has advanced over the years.

Section: /computers (RSS feed) | Permanent link | 3 writebacks

Tue, 10 Jul 2007

Technical Museum

On Sunday I have visited Brno Technical Museum with Iva. I have not been there for maybe ten years. I think last time I was there was when the museum was still located in the centre of the city.

The museum is large, especially for a child like Iva, who get easily tired. We have only visited two expositions: an exposition of steam engines (they even have working models, propelled by compressed air instead of steam) and water turbines (which was a primary reason of our visit there, because Iva had seen a picture of a turbine in some book, and instead of trying to explain the workings of the turbine to her, I have decided to show a real thing to her).

The most interesting part of a museum, however, was the Experimentárium, a hall with real technical or physics experiments (like soap bubbles, parabolic sound reflectors, Foucault pendulum, photoelectric cells, etc.). Iva really liked this.

In my opinion, the Technical museum is worth visiting, and Iva really liked it. Recommended for everybody but technology haters.

Section: /personal (RSS feed) | Permanent link | 2 writebacks


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