No step back!

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Summary

We'll have a leap second insertion at the end of June this year. My tests and other evidence shows that the Linux kernel in Debian Squeeze (but possibly in newer versions of the Kernel, too, I didn't check the sources) doesn't handle the leap second in the best way, and steps back one second around midnight between June 30th and July 1st. This is a big pain in the… grass 🙂 for time-sensitive applications (e.g.: clusters), or those that rely on a monotonic clock (usually RDBMSs; e.g. older versions of Oracle crashed badly, dunno about newer).

I am trying to find feasible workarounds for this, and I'll keep you posted. … Continue reading →

More cfengine happiness

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Please note: this will be 100% overkill when cfengine 3.3.0 will be out: the new awesome templating engine will make this kind of file editing trivial. Nevertheless, this was buzzing in my head for too long after I read the early release of Learning cfengine, so I wanted to give it a go in any case.

Objective: write a parametrised method to create an ntp.conf file, with all directives in a chosen order, and in a "human friendly" form.

As always, when you want to impose your own order to cfEngine (right or wrong that may be), you have to clearly understand what the normal ordering is, so that you'll have a clear picture of what is defined where. … Continue reading →

The right order in cfengine

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NOTE: the code in this post has been revisited, be sure to read The right order in cfengine, revisited after this one.

I've been playing a bit with cfEngine recently, with different degrees of happiness and frustration. After reading the early release of the super-awesome O'Reilly's Learning Cfengine book, I decided to revise my experiments once again.

One thing I had trouble doing was to push out changes in a configuration file in the exact order I wanted them. Before reading the book it looked too odd and difficult; now it is still looks a bit odd, but doable. Let's see how it works. … Continue reading →

Bug affecting NTP multicast users on Linux

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…and not just them.

It's the debian bug #654876 (CVE-2012-0207), which was introduced in the Linux kernel version 2.6.36, and affects IPv4 Multicast users. In particular, if you are using NTP multicast on that kernel version or higher, you are affected.

This bug seems easily exploitable in a local network, and may be used for denial of service attacks. Patches are available for Linux 3.0.17, 3.1.9, 3.2.1, with Debian porting it to their kernel package version 3.1.8-2.

For more information, see Ben's technical blog

Up-to-date information and tutorials about Perl

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I don't like link collection pages, but I can make one exception for a good reason. And I have one.

A well known star in the Perl community is encouraging Perlers all around the world to give visibility to a number of interesting tutorials and news sites. Too often, obsolete crap pops out of google searches about Perl, and it's time to hint the search engines that there is something newer and better around.

So, for your and my pleasure, here you are:

Perl Tutorials

Perl news