• Linux,  Work

    Improving Mediawiki performance

    Now that I am on the subject of improving performance, I configured some performance improvements for a Mediawiki installation here: Make sure you run the latest Mediawiki version. Mediawiki 1.16 introduced a new localisation caching system which is supposed to improve performance, so you definitely want this to get the best performance. Create a directory where Mediawiki can store the localisation cache (make sure it is writable by your web server). By preference store it on a tmpfs (at least if you are sure it will be big enough to store the cache), and configure it in LocalSettings.php: $wgCacheDirectory = "/tmp/mediawiki"; Iif /tmp is on a tmpfs, you might add…

  • Linux,  Work

    Improving performance by using tmpfs

    Today I analyzed disk reads and writes on a server with iotop and strace and found some interesting possible optimizations. With iotop you can check which processes are reading and writing from the disks. I always press the o, p and a keys in iotop so that it only shows me processes doing I/O and so that it will show accumulated I/O instead of the bandwidth. With the left and right arrows I select on which columns to sort the list. Once you have identified the processes wich are doing much I/O, you can check what they are reading or writing with strace, for example # strace  -f -p $PID …

  • Linux,  Work

    DHCPd failover

    Last week, I set up two dhcpd servers in a fail-over configuration. The goal is that when one DHCP server goes down, the other one takes over so that clients don’t lose their network connection. I read different tutorials on the web, such as this one of a fellow blogger and this documentation published by IBM.

  • Linux,  Work

    Migrating from Microsoft SQL Server to PostgreSQL

    One of the servers I manage at work is still running Microsoft Windows 2000. This system is hosting a few old forgotten web sites and it runs Microsoft SQL Server containing a few databases still in use. This server was already there when I started working at the university. Fortunately I never had to do much work on it and there never was a serious crash: it would have been a serious headache for me restoring this system because I do not have much knowledge about Windows and SQL Server. During some spare time at work I decided taking a look at migrating the MS SQL Server databases to PostgreSQL.…

  • Linux,  Work

    Migrating mail from KMail to Evolution

    At work I am busy migrating some Linux desktop users from an old Slackware 12.0 system with KDE 3.5 to Debian Squeeze with GNOME 2.30. So I had to migrate the e-mails from KMail to Evolution, a task which was not that trivial as you would hope at first. On these systems, the mails were saved in ~/Mail. This directory did not contain a standard maildir structure or mbox files, but some weird mix of those two. I do not know whether this is typical for KMail or whether this was a peculiarity on these systems because the e-mails have been migrated from even other e-mail clients and versions in…

  • Linux,  Work

    A wise server migration

    Yesterday I migrated two servers at work to a new machine. The old machines were pretty underpowered: a Pentium III 1 Ghz system (with 384 MB RAM if I remember correctly) and a Pentium 4 system. The new machine is a Dell Poweredge R410 with a Xeon E5504 processor, 12 GB RAM and a PERC H700 RAID controller (which is actually a LSI MegaSAS 9260) with 3 750 GB SATA disks in RAID 5. The hardware is pretty nice (although I am not happy at all with the way Dell treats its customers, so I will rather prefer other vendors in the future, but maybe more about that in a…

  • Linux,  Mandriva

    Improving battery life time in Linux

    Today I received a new battery for my Dell Latitude E6400 laptop. The old battery (a 6 cell one) only lasted for about 15 minutes any more, 1,5 year after I acquired this system. The new battery is a 9 cell version. gnome-power-manager estimates I should be able to run 6 hours now without a charge, which corresponds with what I expected. Now that I have a new battery, it is time to take a look again at trying to lower power consumption as much as possible. On my system I am using Mandriva 2010.1 Cooker with GNOME 2.30 and laptop-mode-tools 1.54, but this howto should apply (sometimes with slight…

  • Linux,  Work

    Server migration

    Since two days, I have merged the main servers used by two research laboratories at work. One server was an old Linux server which really needed a hardware upgrade, and the other one was a Mac Pro machine running a flaky OS X Leopard. The new server is of course running Linux: Debian Lenny. It was a very interesting experience: working out procedures to migrate the mailboxes (from Dovecot on the Linux server and Cyrus on the Mac server to Cyrus on the new server), finding out how to set up one NIC in two different subnets (especially the routing is a little bit tricky), getting all services hooked up…

  • Linux,  Work

    Updating to Debian Lenny

    Last week-end, Debian Lenny 5.0 was finally released. I use Debian on most servers I manage at work. A few of them were already using Lenny when it was still the testing branch, but most are still on Debian Etch. So this morning I decided to test upgrade one of the less critical Etch systems to Lenny. That system is only used to store back-up files from other systems, so it would not be a problem if that machine was off line for a couple of hours. According to the release notes, you should rather use aptitude instead of apt to upgrade, so that’s what I did. All went well,…