WordPress 3.0 upgrade and the white blank screen

June 18th, 2010

When just upgrading this very blog from WordPress 2.9.2 to 3.0 using the automatic upgrade feature the upgrade succeeded at first. Even showing the admin page for that in the new design.

But then, every page either through the frontend or the admin backend simply showed a white blank screen. So it seems when initializing wordpress something goes horrible wrong. As now usful logs where found in the error log of apache it must be something internal.

Reading a nice post in the wordpress forum which refers to the very same problem lead to the conclusion that probably a plugin gone wild. So to resolve this I started to manually move single plugins to a disabled directory in wp-content/plugins. Which revealed wptuner as the plugin causing this issue. To get your blog back online, simply remove the wptuner plugin for now and you will be back in business.

As your blog might use some other plugins that are not compatible yet, your milage my vary here and you may need to disable/remove other plugins too.
Good luck on your journey to a very nice looking WordPress 3.0.

Build your own (faster) perl

March 27th, 2010

Using the perl that comes with your distribution is usually fine, but it has some limitations. When building a perl for a distribution it needs to be versatile and fit various needs. Therefor ithreads, the perl specific threading implemenation, is enabled there, to allow building modules that require threads to be available.

The downside is, that this threading code adds some quite low-level overhead, which usually means that a perl compiled with threads takes a performance hit of up to about 10%. So it sometimes makes sense to build your own perl, especially if you know it’s going to be used more on the server side, for long-running processes. Saving 10% in CPU cycles means potential for 10% in power saving or giving other processes a chance to run.

Building perl is really straightforward and usually just takes these steps:

  • Download the latest stable Perl from perl.org
  • Unpack it to a temporary directory
  • sh Configure -de -Dprefix=/opt/perl5
  • make && make test && make install
  • Perl is now installed in /opt/perl5

Now you can add any additional modules that you like, some recommended ones are:

  • App::cpanminus
  • Task::Kensho
  • Task::Plack
  • Task::KiokuDB
  • Mojolicious
  • Starman
  • Starlet
  • EV
  • AnyEvent
  • AnyEvent::MP
  • DBIx::Class
  • MongoDB
  • Data::FormValidator

Using the newly built perl just requires to update your path before starting your perl programs:

  • export PATH=/opt/perl5/bin:$PATH
  • /usr/local/bin/myperlprog

After setting the PATH just verify with perl -v that your perl include path points to /opt/perl5 (or any other path you chose).

Resolving LVM: Unrecognised LVM device type 259

March 20th, 2010

Trying to create a md raid1 device for 2 phyiscal 1TB disks failed unexpectedly with a strange (and very undescriptive error, that is only revealed when running with the verbose option (-vvv):

Wiping internal VG cache
/dev/md0p2: Skipping: Unrecognised LVM device type 259
Device /dev/md0p2 not found (or ignored by filtering).

The problem seems to be that the type 259 is simply not recognized, although it is defined in /proc/devices and known as blkext there.
So adding this to /etc/lvm/lvm.conf in the devices section:

types = [ "blkext", 64 ]

After adding this the mdadm command to create the md device succeeds:

mdadm --create /dev/md0 --level=1 --raid-disks=2 /dev/sda /dev/sdb

Setting up your own simple debian repository

April 27th, 2009

In the process of getting a debian repostiry ready to allow easy installtion with debian’s apt, a small series of posts are going to be created here. So here is the initial post describing a very simple debian repository layout.

All that’s required to setup your own debian repository is the dpkg-dev package and a web or ftp server for serving the files. For a local deployement (e.g. within a company) also a file-system based approch is possible through a NFS mounted directory.

Make sure the dpkg-dev package is installed:

sh# aptitude install dpkg-dev

Copy all files into a directory binary on the server. So the layout will look something like this:

+-- debian
    +-- binary
    |   +-- myweb-2.0-1_i386.deb
    |   +-- myweb-utils-2.0-1_i386.deb
    +-- source

Here the packages in the binary directory can new be used to create the repository index and serve this then as a debian repository. To scan the packages and create the index use:

$ cd webserver-root
$ dpkg-scanpackages binary /dev/null | gzip -9c > binary/Packages.gz
$ dpkg-scansources source /dev/null | gzip -9c > source/Sources.gz

Now the repository can be used by adding the following to /etc/apt/sources.list:

deb http://my.server.com/debian/binary ./
deb-src http://my.server.com/debian/source ./

See http://www.debian.org/doc/manuals/repository-howto/repository-howto for more details.

Dual-Screen setup with Xorg, RandR1.2 and ATI 9.2 (v8.528) Linux x86_64 drivers

February 22nd, 2009

After seeing that ATI has released again drivers for Linux with a new major version number (and not the scarry .0 behind it) I thought it was time to battle the ATI dragons again. As Debian usually lags behind on the proprietary ATI stuff (who wonders…) I’m using aain the binary packages provided by ATI.

The system is Debian testing, which is now codenamed “Squeeze” as Lenny finally stablized.
As the build required libstdc++5 I had to reinstall this package:

sh# aptitude install libstdc++5

Downloaded the latest ati-driver-installer-9.2-x86.x86_64.run and ran the usual:

sh# sudo sh ati-driver-installer-9.2-x86.x86_64.run --buildpkg Debian/testing

which results in the following packages being built:

  • fglrx-amdcccle_8.582-1_amd64.deb
  • fglrx-driver_8.582-1_amd64.deb
  • fglrx-driver-dev_8.582-1_amd64.deb
  • fglrx-kernel-src_8.582-1_amd64.deb

Install those and if RandR 1.2 is compiled into Xorg (which it is usually) your dual-screen setup probably switches back to a cloned view. In case you never had a working dual-screen (called big desktop by ATI) setup, run the following (and be sure to backup your /etc/X11/xorg.conf in case you have anything special in there), otherwise skip this section:

sh# sudo dpkg-reconfigure -phigh xserver-xorg
sh# aticonfig --initial --desktop-setup=horizontal --overlay-on=1

Then be sure to have added a “Virtual” desktop size to your “Display” subsection like so (for two 1680×1050 screens thats 3360×1050):

Section "Screen"
        Identifier "aticonfig-Screen[0]-0"
        Device     "aticonfig-Device[0]-0"
        Monitor    "aticonfig-Monitor[0]-0"
        DefaultDepth     24
        SubSection "Display"
                Viewport   0 0
                Depth     24
                Virtual   3360 1050

After restarting X11 (Ctrl-Alt-Backspace) login and open a terminal and run:

sh# xrandr --output DFP2 --right-of DFP1

This will setup display DFP2 to be right of DFP2, please check the correct display names to use with

xrandr -q


Of course you can also use the graphical tools arandr or grandr to accomplish this.

  •   Category: Bits & Bytes   A-Tags: ,
  • Comments Off on Dual-Screen setup with Xorg, RandR1.2 and ATI 9.2 (v8.528) Linux x86_64 drivers

Starting up QuikIT…

September 15th, 2008

Das neue Einzelunternehmerprojekt QuikIT geht an den Start.

Nach doch inzwischen einigen Jahren der minimalen Zeitinvestition in diverse IT-Dienstleistungen soll nun das ganze in einer organisierteren Form von statten gehen und auch die Möglichkeit schaffen größere Projekte (wie eben http://www.quikplan.at) umzusetzen.

Fokus wird anfangs sicher auf:

  • Web-Hosting für Private, Vereine und Kleinunternehmen
  • Domain-Registrierungen verbunden mit obigem
  • System-Administration (Linux, MySQL, PostgreSQL, Virtualisierung)
  • Beratende Tätigkeiten im Bereich Linux, High-Availability mit Open Source, Virtualisierung, Datenbanken und auch der OpenSource Einsatz im Unternehmensumfeld

Mehr unter http://www.quikit.at

Next »