Profiling MySQL/MariaDB queries

If you ever face an optimization issue in MySQL or MariaDB and want to know how to measure/benchmark the differences in execution between two queries, you should definitely know about the set profiling=1; command. Here is how it works: mysql>…

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The Drupal 6 bootstrap easy debug

Just as a self reminder, and because I don’t fancy too much looking into the Drupal core for debugging, here is a short explanation of how the Drupal 7 bootstrap mechanism works. First of all, a bootstrap mechanism is a…

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Howto redefine the hostname on Debian/Ubuntu

Just a small procedure as a self-reminder (I seem to have to use it just seldom enough to forget it each time – thanks Marvil): define the new hostname on the 127.0.0.1 localhost line (after localhost) in /etc/hosts set the…

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Renew expired self-signed SSL certificate

For some reason, it might be very difficult to find information on how to renew a self-signed certificate. This is a nice (and short) explanation: http://linux.togaware.com/survivor/Renew_SSL.html. Please note that a .pem file is in fact (as you can guess from…

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Prune a Mercurial branch

The manual is perfect for that… http://mercurial.selenic.com/wiki/PruningDeadBranches All you have to do is: hg heads Identify the branch you want to close (get the revision number, let’s say 951) hg update -C 951 hg commit –close-branch -m “This version never…

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Chamilo big files upload fails on some cPanel

Recently I’ve had to fix a very strange cPanel installation of Chamilo. For some reason small files could be uploaded but not large files. Modifying the .htaccess file to add post_max_size and upload_max_filesize didn’t work. The problem was due to…

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Reset mailman admin password

To reset a mailman admin password on Debian, the easiest way is to locate the mailman’s proper bin directory (use dpkg -L mailman), generally: /usr/lib/mailman/bin There, you’ll find an executable script called change_pw. Use this one. If you want to…

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Server stalled on Loading Kernel Modules without chroot – What to do?

Today we had a server stalled on “Loading kernel modules” at reboot (after adding 12GB of RAM, to 24GB total). The datacenter didn’t know what to do and they put us on a 32-bit rescue mode console from which we…

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HOWTO Build your own binaries of PHP Xapian bindings for Debian

Due to a licensing issue, the PHP bindings for Xapian were removed from Debian Squeeze. See http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=513796 for more information about this. Though, it is not really hard to build your own package from source. Here is how: sudo apt-get…

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Adobe Flash and V4L2 webcams

Many new videoconference systems nowadays are Flash-based. Of course, the main input for them is some sort of video device (e.g. a webcam). Under Linux, the framework responsible for this is Video4Linux (V4L), of which version 2 (aka V4L2) is…

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