DanNorth.net

So it’s that time of year again. I’ve got a number of conferences and workshops coming up, ranging over all sorts of topics. I just popped over to Martin Fowler’s site (I’m doing a talk with him this week) and noticed that he has a much more organised setup than me. All his events are in a sidebar and there is a handy link if you want more details. Another idea to go on my to-do pile.

ThoughtWorks Quarterly Technology Briefing

• Manchester – 12 September 2007 <-- That’s this week!
• London – 20 September 2007

This is the second instalment in ThoughtWorks series of informal sessions aimed at technologists across the spectrum. Although calling it a technology briefing is a bit inaccurate because the title for this one is “How to Sell Agile to your Organisation”, which has far more to do with the themes of people, risk and change than with anything technological.

This is the talk I’ll be presenting with Martin so I can guarantee a lively session. In his own words: “As I detest selling anything to anyone it will be interesting to see how this talk works out.”

Details and registration info are on the ThoughtWorks website.

RailsConf Europe

• Berlin – 17-19 September 2007

A lot of Ruby folk seem to have taken to behaviour-driven development. This is almost entirely due to the success of the rspec project, which is in turn due to the enthusiasm and dedication of its developers and the community they have established.

A while back I wrote a story-level BDD framework for Ruby called rbehave which has since been integrated into the rspec project.

I’ll be helping rspec project leads David Chelimsky and Aslak Hellesoy present a workshop entitled A half-day of behaviour-driven development on Rails, where we’ll be demonstrating how rspec helps you write software that is focused on achieving an outcome. It’s at 8:30am on the Monday morning, so make sure you’re there first thing.

Expo-C Roadshow

• Växjö – 15-16 October 2007
• Karlskrona – 17-18 October 2007

Expo-C is one of my favourite events. It’s a small conference in south-east Sweden and it seems to attract an audience that really cares about what they are doing. I’ve done two of them now, on very different topics, and on both occasions I was very impressed with the quality of the attendees and the calibre of the other speakers. (I’m usually the only one there who hasn’t written a book.)

This time they are doing two mini-conferences back to back, in Växjö and then Karlskrona, with a tutorial day and a seminar day (six sessions) in each location. I’ll be running full-day tutorials on BDD in Växjö, and Coaching, Communication and Change in Karlskrona. For the seminar I’ll be talking about bridging the communication gap, based on a keynote I gave with Martin Fowler at QCon earlier this year.

I will also be learning how to pronounce “Växjö”.

OOPSLA

• Montreal – 21-25 October 2007

This will be my first OOPSLA. I’ve heard a lot about it and I’m a bit intimidated. By reputation it seems a bit more “cerebral” than most conferences. It will also be the first time I’ve ever presented JBehave at a conference. No mean feat considering I started writing it at the end of 2003! There’s perpetual beta for you.

My co-presenter is my ThoughtWorks colleague, friend and cybergoth Liz Keogh, the person responsible for getting JBehave to 1.0. I have huge respect for Liz; she manages to combine software with poetry. This isn’t a pretentious metaphor – she actually does combine software with poetry. She ran a haiku workshop at a previous ThoughtWorks away day that many of the attendees nominated as the highlight of their day. She also writes inspiring and inspired blog articles.

I’m only going because I want to see what Liz does when she’s let loose on a roomful of developers. I reckon we’ll end up writing haiku acceptance criteria.

And some others…

There are another couple of events in the pipeline that I will blog about nearer the time (January and February next year). After that I’m going to have a bit of a lie down.

Correction: I got the dates wrong for OOPSLA. Thanks Joshua Graham for putting me straight.
Another correction: My Swedish geography is appalling. Thanks Morgan Persson.

This is the first of an occasional series of posts about Linux systems administration. I’ve been an on-off Linux sysadmin for about, well, my first Linux was Slackware on a stack of 3.5” floppies. Every now and then I do something “fiddly” and I want to capture these episodes in case I ever need to do it again, or in case someone else wants to and they find this useful.

I run Debian Testing on kenny, the server that hosts http://dannorth.net, http://behaviour-driven.org and a bunch of other websites, blogs and wikis. (Random plug: it’s hosted by the fine folks at SolarVPS. I have no affiliation with them but they rock.) It seems a good balance between Debian Stable – which is rock solid but always about a year out of date – and Unstable, which requires updating far too often and hosed my old server (cartman – can you see a theme here?).

Mostly it Just Works. In particular WordPress and MoinMoin are a joy to configure and use. I get change out of about 10 minutes to add a new blog.

I also use it as a mail server, using postfix for sending and receiving mail and courier-imap for reading it. I tried a number of mail servers and settled on postfix after dismissing sendmail and qmail as just too complicated and exim after staring at the impenetrable documentation one time too many.

I found it pretty easy to set up secure SMTP over TLS and secure IMAP over SSL, but I stumbled at setting up virtual mail addresses. This article is about how to do that using postfix and courier-imap. It’s pretty straightforward once you know where all the moving parts are, but they were less than obvious to me.

Virtual mail addresses

Mostly you send email to bob@address.com and it turns up in bob’s mailbox in bob’s login account. Sometimes you don’t want this. For instance, I host about 20 domain names on kenny, and addresses like info@blah.com or sales@blah.com need to go to specific people. That’s the first type of virtual addressing, known as virtual alias domains.

The second case is “more” virtual – the user doesn’t even need to exist on the server with a regular login account. Postfix puts the mail into a special directory, and courier-imap presents that directory as the mailbox when the user “logs in” over IMAP. This is where all the moving parts come in. This is known as virtual mailbox domains.

Setting up postfix for virtual alias domains

This is the easier of the two, since the mail ends up in a real email address, so there is no corresponding configuration on the courier-imap side. This information came from the Postfix Virtual Domain Hosting Howto.

In /etc/postfix/main.cf add the following lines:

This says that postfix will treat the name dannorth.net as a virtual alias domain and will use the file /etc/postfix/virtual to do the mappings. Your /etc/postfix/virtual might look like this:

Once you have this file configured, run the command:

to create the hash database that postfix will use, then run:

to update the configuration.

Setting up virtual mailbox domains

Ok, there are several moving parts here. We need: * a directory to deliver the mail to * to tell postfix to deliver it there * to enable virtual users in courier * to tell courier where the virtual users’ mail lives

In this example, I’ll set up two virtual users, fred and barney, at example.com.

System accounts and directories

The virtual users’ files need to be owned by someone, so we’ll create a “fake” user and group. I’m using vmail for both the user and group names, with uid and gid both set to 5000.

From a root prompt:

Configuring postfix for virtual mailbox domains

In /etc/postfix/main.cf

This is pretty self-explanatory. It says example.com is a magic virtual mailbox domain, all users and groups map to a fixed number (you can get cleverer than this but I’m not worried about it for now), and that all the interesting stuff is in /etc/postfix/vmailbox. The minimum uid is postfix’s safety measure in case I do something stupid. It means I can’t accidentally let someone have access to system files.

Now let’s look at /etc/postfix/vmailbox:

The magic here is the / at the end of each line. This says to use maildir format (the format courier-imap is expecting) rather than clunky old mbox format. Postfix will create the appropriate directory structure for fred and barney,

Again we create a hash of this for postfix:

Phew! That’s the postfix side done. Now stop for a cup of tea.

Configuring courier-imap for virtual mailboxes

On Debian, courier imap runs as three executables, each with separate init.d scripts. courier-imap and courier-imap-ssl are the imap servers themselves (I run courier-imap bound to localhost for webmail). courier-authdaemon is the chap that does all the authentication. That’s the one we’re interested in.

Firstly, we need to enable virtual users. In the file /etc/courier/authdaemonrc you need to make sure your authmodulelist setting contains authuserdb as one of its authentication mechanisms. Mine looks like this:

Don’t forget to tell the auth daemon you’ve made a change:

Courier uses a file called /etc/courier/userdb to store virtual user mappings, but you don’t usually edit this file yourself. It has an arcane format (using tabs and pipes as delimiters) and should be left well alone. Instead, courier provides you with some command line tools to manipulate it.

To create an entry for fred, we do this:

(That should all be on one line – your browser might wrap it.) Then set a password for fred:

Do the same for barney. Finally we build the hashed user database that courier will actually use:

Note: don’t forget to run makeuserdb after making any changes to the virtual user data otherwise courier won’t know.

Testing the configuration

Firstly, try sending an email to the virtual user. Postfix should create the maildir structure under example.com/fred. Then try connecting to courier to read the mail. If you find you are getting authentication problems from the courier side, you can try setting DEBUG_LOGIN=1 in /etc/courier/authdaemonrc and restarting the auth daemon. Don’t forget to switch it off again once it’s working.

Earlier this year I wrote an article to introduce service-oriented architecture to non-technical people. It was published in the May 2007 issue of Better Software magazine.

The kind folks at Better Software have allowed me to provide a PDF version of the article, complete with retro 1950s graphics. You can also read it as a single html page.

Please post any comments here, because I’ve disabled comments on the page itself.