Makura no Soshi

It is still one of the first questions when installing a unixoid OS: do you still need a swap partition and how big should you make it. In the old days™ this was an important question because disk space was expensive and the OS memory management had several constraints.

Today both memory and disks are cheap enough to make this question insignificant in many cases. One can usually buy enough memory to prevent swapping, and with terrabyte disks it makes no real difference whether the swap partition is 1 Gb or 4 Gb in size.

I still use the old rule of thumb and allocate twice the size of RAM for a swap partition. But the intention is not so much to swap memory pages but rather to always have enough space for kernel core dumps. My basic reasoning is:

1. In case of kernel errors I want to get a core dump.
2. A later RAM upgrade is relatively cheap and easy, thus probable over a system’s lifetime.
3. A later disk re-partitioning is more difficult, thus to avoid.
4. Disk space is cheap, allocating ≤ 5% for a mostly unused swap partition has no significant cost.

Note: This syslog entry is puzzling if the system has no program named try, but no cause for concern:

2011-11-19T01:31:21 frodo kernel: pid 47812 (try), uid 0: exited on signal 10 (core dumped)

Source of the program is Perl’s Configure script, which compiles its C library test cases into programs named try. And apparently amd64 systems need to use the function va_copy() because the test case without this function leads to a segfault.

Nach einem Schreib-Endspurt im August und folgender Schreib-Faulheit im September soll es auch hier mal wieder weitergehen. Und bevor sich wirklich neue Themen finden, gibt’s noch ein paar übriggebliebene Notizen zu meiner Diplomarbeit: Design and Implementation of an IPv6 Plugin for the Snort Intrusion Detection System.

[Short english explanation:] I finished my diploma thesis: Design and Implementation of an IPv6 Plugin for the Snort Intrusion Detection System.

Finally got around to read the OSX Lion review on ars technica… The most interesting feature is the new process model with automatic and sudden termination (at least in regard to OS design; without having a Mac I no longer care about the UI).
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Perl and Python are not only useful for Unix programming. Both languages work on Windows, have modules for Win32 APIs and their programs can be packaged into .exe files.

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What makes good code and why is some code better than others? One quantitative approach to answer this is the use of software metrics. These metrics try to capture the size and complexity of code in numbers (e.g. ‘lines of code‘, ‘cyclomatic complexity‘) and can be useful indicators for maintainability and simplicity (or more often the lack thereof).

I found three ways to get complexity measures for PHP code.
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This is a nice idea and proof of concept: spreading malware in BibTeX files.

Probably every TeX-User knows the advocacy about how powerful the language is… but do (or can) you proofread everything before you compile it?

Recently I replaced my office’s filtering network bridge which still ran on an old FreeBSD 4.11 box for the last eight years or so. The new system is based on a Soekris 5501, and because it took some time to choose the right software I decided to publish my notes on the tested BSD firewall products.
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