I just spent a couple of days, on and off, fiddling with my apache setup on a kubuntu box. I had a site with some very weird and scary rewrite rules which I needed to do some development work with and I just could not get the site to work!

The solution was very simple and I found the answer in this post about ubuntu and apache. Basically, AllowOverride is set to None for both / and /var/www/ by default on ubuntu, which is nice and secure but it caught me out on this occasion. Change the settings to AllowOverride All and create a symlink in mods-enabled to mods-available/rewrite.conf and restart apache – everything should then start playing nicely.

I write on technical subjects on this site on a fairly regular basis, and nothing annoys me more than blog software which “eats” long lines of code or renders it in a difficult-to-read way. Happily Serendipity (or s9y for short) has a plugin for geshi.

About GeSHi

I thought “geshi” was a word but I just looked it up to link to it and it turns out its actually GeSHi (Generic Syntax Hilighter) which is a very humane way of pronouncing the thing. It is a very popular way to render source code on the web and was originally intended for phpBB. Geshi is great, it has lots of pre-made syntax highlighting rules so the odds are that it can probably already render whatever language you are coding in very nicely, however if it doesn’t then that’s fine too – it is an open standard and you can jump in and write your own.

Using GeSHi

Back to this blog, I added the “Markup: Geshi” plugin from SPARTACUS (the serendipity plugin repository) and added it as an event plugin. I had a lot of problems getting it working – putting it first in the list of event plugins eventually did the trick for me. You use geshi by adding geshi tags around the code you want to show, for example:

phpinfo();

phpinfo();

Styling GeSHi

Another problem I had initially was with the default resulting fonts, however these are easy enough to change and I now have colours I chose myself (illustrated in my posts about a SOAP server and PHP compilation) which is really quite easy to do. The plugin has files with all the language highlight in them and if you scroll down and look at the “color” entries towards the end of these, it is possible to just replace the red/green/blue defaults with colours that fit in with your look and feel (pink in my case, obviously!). For me the syntax files are in serendipity/plugins/serendipity_event_geshi/geshi – this is also a good place to look to see what languages you have that are supported.

I commonly use:

• php
• bash
• xml
• sql

A useful tip for styling is that the code block is placed into a div with a class named the same as the “lang” attribute – so for example I’ve got some of them resized by adding an entry to my overall css file.

Hope this helps someone, I remember having problems finding much info about using geshi in this way when I first added the plugin. If anyone is having problems feel free to post comments, I have this working on my serendipity installation so I am happy to try to help out.

I switched over to serendipity as my blog platform about 6 months ago and although I haven’t been blown away by it, its a better tool for this job than textpattern was. I liked textpattern a lot but serendipity is better for what I need. There were a few things that I really missed when I moved across to serendipity – and the biggest one was textile as a markup. Its available in serendipity as a plugin, and I’d recommend it to everyone, but after I had imported my existing content from textpattern to serendipity I found that turning on the markup plugin did strange things to existing content so I turned it off.

Another thing I’ve been missing is the ability to add markup in comments, such as images. Well, its back! I’ve turned on textile for comments on this site, there is a link under the comments box to a page that shows you the syntax, so feel free to add richer content to this site from now on :)

I recently downloaded a virtual machine which had all the default factory settings in it – including an American keyboard layout. To change this on Debian Etch I simply used:

dpkg-reconfigure console-data

and then followed the online prompts. For reference (i.e. the next time I have this problem), the | (pipe) symbol on a US keyboard is mapped to the ~ (tilde) on a UK one.

I’m installing Kubuntu Gutsy Gibbon onto my Dell Vostro 1500 and the first problem I hit was that the Live CD was entirely unable to repartition the disks. There are a few partitions on the disk (as you’d expect from a Dell machine running Vista, its got recovery and things) and I kept seeing the error:

An error occurred while writing the changes to the storage devices.
The resize operation is aborted

To get around this I resized the main partition in Windows and created a new partition but left it unformatted. When I went back to the Live CD install I got the option “Use largest contiguous space” and that worked fine.

Hope this helps someone!

Last night I attended the first Manchester Girl Geek Dinner. I am very excited about the Girl Geek Dinner events arriving in the north, there’s a lot of activity up here and I’m already involved in other local events such as GeekUp and BarCamp.

I’m based in Leeds, so it was about an hours drive over to Manchester. Thanks to the wonderful world of satellite navigation, I found the venue with no problems. The evening started with some mingling and drinks, and then we were all invited to take seats and help ourselves to the buffet, which was excellent. After the meal we had a variety of talks which were actually really good, I hadn’t been thinking of the talks as the highlight but they certainly were!

During the course of the drinks, the meal, and a few minutes after the talks (although it was a very late finish, 10pm or so, I didn’t leave until half past and then had to drive back to Leeds), I was able to meet and speak with an amazing selection of women of various ages, professions and backgrounds and had some interesting and valuable conversations.

Its early days for this version of this event and the plan is for it to be quarterly, I am looking forward to the next installment.

I recently got an email from a BarCamp friend, Mark Sailes, telling me about his new site http://www.svn-checkout.co.uk. I am a big fan of subversion and always looking for more tips and tricks for using it better so I popped over to have a look. Its a nice site with some very useful short articles on various subjects related to subverison. In particular the article on releasing new versions of sites caught my eye. Mark suggests use of a checked out version of code rather than an exported one, and using the switch command to upgrade to the next tagged version as needed. He completes the setup with an apache configuration trick to avoid any of the subversion information being served to the outside world. I’ve usually just exported new versions as needed but this trick is a definite alternative and the article itself guides the reader through each step of the way. Nice one Mark :)

For a few weeks now, I’ve been seeing this error in my logs every night:

/etc/cron.daily/logrotate:
error: error running shared postrotate script for /var/log/mysql.log /var/log/mysql/mysql.log /var/log/mysql/mysql-slow.log
run-parts: /etc/cron.daily/logrotate exited with return code 1

What’s happening is that after all the mysql backing up and everything is done, ubuntu is trying to use the debian-sys-maint user to flush the logs, this is actually called in /etc/logrotate.d/mysql-server. On my system, we seem to have lost this mysql user.

The solution is to look for the password used in the /etc/mysql/debian.cnf file, mine looks like this:

# Automatically generated for Debian scripts. DO NOT TOUCH!
[client]
host     = localhost
user     = debian-sys-maint
password = xxxxxxxxxxxxxxxx
socket   = /var/run/mysqld/mysqld.sock
[mysql_upgrade]
user     = debian-sys-maint
password = xxxxxxxxxxxxxxxx
socket   = /var/run/mysqld/mysqld.sock
basedir  = /usr

Using the password, and some inspiration from this post on the Ubuntu Forums I recreated the user with the necessary permissions and password with:

GRANT RELOAD, SHUTDOWN, PROCESS, SHOW DATABASES, SUPER, LOCK TABLES ON *.* TO 'debian-sys-maint'@'localhost' IDENTIFIED BY PASSWORD 'xxxxxxxxxxxxxxxx'

This did the trick, as the nightly errors have now disappeared from my script. Hope this helps someone in a similar situation – if you can expand these notes then please add a comment and I will update this as needed – thanks :)

I had a situation recently where I was outer joining one table onto another. I needed all rows from the first table, plus any matching rows from the second table. So:

SELECT * 
FROM table1 t1
LEFT JOIN table2 t2 ON (t1.col_a = t2.col_a)

So far, so good, right? In this particular instance though I wanted to filter my results on a particular criteria so I added something like:

SELECT * 
FROM table1 t1
LEFT JOIN table2 t2 ON (t1.col_a = t2.col_a)
WHERE t2.col_b <> 42

This is where it all started to go a bit weird. I wanted all the rows from the first table, plus anything from the second table that matched but didn’t have col_b equal to 42 (this is a rather contrived example I know but my real-world example was so complicated I’d still be explaining it if I started). The syntax above was causing a problem in the case that there was a single matching row in the second table which matched the criteria in the where clause. In this instance, the entry from the first table would appear once, and then immediately get filtered out by the constraint in the where clause.

What I actually needed to do was filter the second table before the join happens. So here’s the syntax:

SELECT *
FROM table1 t1
LEFT JOIN table2 t2 ON (t1.col_a = t2.col_a AND t2.col_b <> 42)

It turns out that you can use the ON clause when you join to include anything that you would usually put in a where clause to restrict the rows on the table that is being joined. Hope this makes sense and is useful to someone, add your comments if you have any!