GUADEC 2010

I was at GUADEC this week so here is a summary of what I took out of it.

The Location

GUADEC was held in The Hague this year and hosted by De Haagse Hogeschool. The Hague is a nice medium sized town where, in typical Dutch fashion, you go everywhere by bicycle or tram. Public transport is very efficient, fast and always on time. In short, the only similarity with London is that the weather was cold and cloudy most of the time we were there. De Haagse Hogeschool is a great space for such a conference, with good rooms for the talks and a great space to mingle with people during breaks. However, the restaurants around the venue were clearly not used to having that many customers and I missed the afternoon keynote talks both on Thursday and Friday when it took longer than expected to have lunch. On the other hand, lunchtime was always spent with a bunch of very interesting people so no harm done there.

The Talks

As there were different streams running in parallel, I didn't go to all the talks. Also, I may have completely missed the main point of any talk so what follows is my take on things. It may be biased, incomplete or outright wrong due to me misunderstanding something or other.

GNOME, the Web and Freedom, by Luis Villa

Luis is a lawyer at Mozilla and a geek. His premise is that since the first GUADEC in 2000, a universal platform built on open source software has appeared on every computer on the planet and it's a platform upon which Microsoft is actually struggling to keep up with the competition. It's not GNOME, it's the web. And it's not a fad, it's here to stay (despite what the star formerly known as the star formerly know as Prince might say).

Luis suggests that we should strive to make GNOME Shell the best shell for web applications. All GNOME applications should embrace the web and integrate with it. And when you write a new application, you should write it in HTML and JavaScript first.

I completely agree with the idea of integrating the web into the desktop. A photo management application for instance should be able to seamlessly integrate with services like flickr so that you don't have to leave your desktop to upload photos to flickr or to subscribe to someone's photo stream. In practice, this is what The Web Standards Project have been pushing for some time in the form of the semantic web.

I disagree with the idea to write all applications in HTML and JavaScript because that would significantly reduce developer freedom and flexibility in writing those applications. Also, HTML and JavaScript are just a tool, are well suited to some applications but not all of them.

Finally, there is on aspect which I believe Luis is very aware of: I want to know where my data is hosted and be able to make sure that some of my data is exclusively hosted on my own machine, not somewhere in the cloud. That sort of issues will need to be addressed if the desktop platform we use is to integrate more closely with the web.

Who Makes GNOME? by Dave Neary

This talk sparked a bit of controversy. Dave presented the results of the GNOME Census report. This report produced some statistics on the people who contribute to GNOME in the form of commits to the repositories. The idea was to understand better who contributes to GNOME and how much of it is contributed by paid developers.

Obviously, the fact that Red Hat accounts for 16.3% of the total and Canonical accounts for just over 1% sparked controversy with people saying that this was the proof that Canonical didn't contribute. We're talking about statistics here so as usual they don't tell the whole story and I feel it is very dangerous to draw any conclusion from them. Dave is very aware of the fact and took great care in including caveats in his presentation. That didn't prove enough to prevent the controversy though. So here's my take on what aspects of the statistics show that they should be taken with a pinch of salt:

• The top 2 contributor categories are Volunteer and Unknown and between them represent more than 40% of the contributions. Those people may have become contributors for a variety of reasons and some of them may be from Canonical or Red Hat or any other company, or may have become individual contributors as a result of using Fedora or Ubuntu, we just don't know.
• There are 11 companies between 1 and 3% (ranks 6 to 16). A small change in the number of contributions could change the list dramatically.
• Counting commit events only tells part of the story and focuses exclusively on the development effort. From my experience, in order to deliver projects, packaging, testing and bug management is as important as development. And so are specifications, usability studies and artwork. As a community, in order to deliver the best operating system possible, we need all of the above. Ubuntu (and by extension Canonical) has been very successful in addressing the non-development aspects of delivering a great operating system based on great open source software. And I'd rather Canonical concentrated on working on the areas where the community is lacking resources and experience than add more resources to the bits that are already well covered.

State of the GNOME 3 Shell, by Owen Taylor

I have very few notes on this talk, it basically amounts to: some stuff works, some doesn't and it's still a work in progress.

Shell Yes! Deep Inside the GNOME Shell Design, by William John McCann and Jeremy Perry

Another talk where my notes are less than of stellar quality. The idea is that the GNOME Shell developers are here to make GNOME great. And indeed, the demos look fantastic and are very encouraging. A lot of thought has gone into the interface and I think for the most part, it will make application management, from a user's points of view a lot smoother. On the other hand, some bits and bobs look like the same old things re-hashed, in particular how notifications are handled. I'm not sure how Ubuntu will integrate that as they seem to go the opposite way from what Ubuntu has been doing in this area. Time will tell.

GNOME State of the Union, by Fernando Herrera and Xan Lopez

What more to say than absolute genius? There's no point in me telling you what happened, you needed to be there.

Clutter State of the Union, by Emmanuele Bassi

Clutter has a new logo and a new web site. Very interesting is the introduction of ClutterState to provide declarative state changes and animations. The latest implementation also makes use of the GPU if available. Very, very cool technology and it's what makes MeeGo rock!

So you think you can release? by Emmanuele Bassi

This was a very interesting talk and it made a lot of excellent points in how to handle the release of library code. A lot is also applicable to end user applications and everything is equally applicable to open source and closed source code. The main ones I took out of it are:

• Any new version of the library should not break apps written with older versions.
• Use the 0.x cycle to refine and optimise the release mechanism.
• Have reliable release cycles, such as time based cycles (e.g. every 6 months) and stick to it even if it means dropping functionality from a given cycle.
• Write performance test suites and run them.
• Replying RTFM to questions implies that you've actually written the manual.
• Write a coding style guide and require that patches follow it. I would add to that: keep the coding style short and don't diverge too much from what other projects do otherwise contributors will have no incentive to read it or abide by it.
• When using the phrase patches welcome, make sure that this is really the case and that when someone contributes a patch you actually review and integrate it quickly.
• When releasing version 1.0, commit to the smallest subset of your API as possible and review it thoroughly: whatever is left behind, you will have to support for some time to come.
• Analyse what part of your API your users use most: is it the low level API or the convenience API? If an API turns out to be wrong, don't hesitate to deprecate it.
• Don't develop on the master branch: it needs to build at all times.
• Resist the urge of changing an implementation too often.
• Plan for next minor release but also the next major one.

That's quite a list and I agree with all of it!

Multitouching Your Apps, by Carlos Garnacho

A very interesting talk by Carlos on how to integrate multi-touch abilities in GNOME applications. There is a whole new API for that, that basically allows you to specify the device to use rather than assume that there is a single keyboard and mouse connected. The low-down is:

• Each finger gets a device;
• Devices emit individual events;
• There is a need to gather and correlate event:
• obtain an event packet,
• calculate the distance and relative angle between 2 events,
• use GtkDeviceGroup and multi-device-event signal.

If you want to play with it, you will require XOrg 7.5 and you can get the code through git:

$ git clone -b xi2-playground git://git.gnome.org/gtk+

GNOME 3 and Your Application, by Dan Winship and Colin Walters

A quick introduction on the changes brought by GNOME 3. My take on it:

• No GNOME 2 API will be removed so GNOME 2 applications should keep working with GNOME 3. However, you will need to use a set of new API to take full advantage of GNOME 3.
• The .desktop will be much more central to the application, will act as a unique ID for it and will provide more features. In particular make sure, to include the StartupNotify=true option.
• Provide high resolution icons as icons will be displayed much larger.
• There will be less chrome in application windows.
• No more tray icons (well, they will be done differently).
• Notification tray at the bottom.
• No more libnotify.

Open Design Thinking Workshop, by inventedhere.de

Thanks to Andrea Scheer, Sophia Klees, Andreas Weigt, Martin Steck and Clemens Buss for a very inspiring workshop! I failed miserably at my task in the warm-up LEGO exercise. We all had a lot of fun and I think we came up with interesting concepts. If I find the time, I'd love to try to implement some of what the team I was working on came up with.

Tracker's Place in the GNOME Platform, by Martyn Russell

Tracker has evolved a lot since version 0.6, which is the one available in the Ubuntu Lucid repositories and a is a lot less resource intensive than it used to be. It provides application with the ability to share all sorts of data and is standards based. It also has a brand new query interface in the form of tracker-sparql which looks very powerful.

In practice the tracker database provides functionality which is very similar to what Desktop Couch provides, which is what is installed by default in Ubuntu. Tracker does not provide the replication facility but it provides more comprehensive search facilities. The other difference is that Tracker is designed to store non-application specific data (such as meta-data on an image, which should be available to any image management or manipulation program), while Desktop Couch includes application specific data such as preferences, as well as non-application specific data. I don't think the two are incompatible though and creating a Desktop Couch back-end for Tracker could be very interesting and provide a solution that is greater than the sum of its parts.

Identifying Software Projects and Translation Teams in Need, by Andre Klapper

Andre presented an interesting research he did based on code commits and bug activity to try to identify projects and translation teams that were in need of help in GNOME, the results of which can be found online. It still leaves a lot of questions on how to help those projects but identifying them is an essential first step.

Embracing the Web: Integrating Web Services within GNOME, by Rob Bradford

Rob presented libsocialweb, which is used in MeeGo to provide integration to web services such as Facebook and flickr. And there were demos aplenty: very entertaining! Oh and GeoClue looks really cool too.

GNOME Color Manager: Exploring the User Experience and Integration Points for a 100% Colour Managed Desktop, by Richard Hughes

For professional graphic artists, it is essential to have proper colour management throughout the complete image workflow, from the source (camera or scanner) to the output (printer or PDF file). OS-X does that to perfection, Windows 7 does it but not very well, Linux doesn't do it at all. Richard proposes a set of tools and libraries to change this and make the GNOME (and possibly KDE) desktop fully colour managed. Great stuff!

Cairo: 2D in a 3D World, by Christopher Paul Wilson

Maybe it was burnout from 3 days of conference but I found this talk the least interesting of all. All I took out of it was that there are a lot of reasons why Cairo hasn't released a new version for a long time, if Cairo is slow it's because the drivers are broken or developers are not using it properly and it's all going to be better very soon now as they move to a 6-month release cycle.

Anyway, moving on swiftly...

Growing Communities with Launchpad: Ubuntu and GNOME, by Danilo Segan

Danilo's talk was all about how to use Launchpad better to ensure that we can get related communities (such as Ubuntu and GNOME) to work together better. It concentrated particularly on bugs and translations. I think that, as a result of a question I asked, I volunteered myself to contribute code to Launchpad in order to simplify forwarding bugs upstream.

The Parties

Nearly as important as the talks were the parties: it was the opportunity to meet people I'd only ever heard of or talked to via email or IRC.

Canonical Party

The indefatigable Jorge Castro made sure that the party was a success. The music was a bit loud at times but considering it was held in a night-club, it was to be expected. It also proved that the best DJ in the world would find it hard to get a group of geeks to dance.

Collabora Party

The beach party organised by Collabora was great. Less loud music than the Canonical one and a nice barbecue. It would have been perfect if the weather hadn't been cold and windy. We also got to be initiated in the correct Dutch etiquette regarding the use of satay sauce at barbecues: just drown everything in the stuff.

GUADEC After-party at Revelation Space

This hacker space is just great and it was a nice way to wind down.

Shotwell Hacking

It was a pleasure to meet Adam, Jim, Rob and Lucas from Yorba while at GUADEC. We talked a lot about Shotwell and with Jim's help I finalised the code to migrate photos from F-Spot, which Jim committed in trunk. There are a couple of follow-up bugs that were reported by early testers but the bulk of the functionality made it in before the string freeze and the rest should be sorted in time for the release of Shotwell 0.7, which will them make it into Ubuntu 10.10.

Next Year

Next year, GUADEC and Akademy will join forces for a desktop summit in Berlin.

Converting OpenOffice Documents in Bulk

I had a request from a customer earlier this week: they wanted a copy of all the diagrams that are present in a specification I've been writing for them. All those diagrams are in separate OpenOffice Draw (.odg) files. They don't use OpenOffice but were happy to have PDF versions. The only problem is that there are 42 of them so it would take ages to convert them manually. A quick Google later and I found a way to convert documents from the command line.

So, to adapt it to Ubuntu, download the DocumentConverter.py file mentioned in the post above and store it where your documents are. Then, start OpenOffice in headless mode:

$ ooffice -headless -accept="socket,port=8100;urp;" &

As the version of Python installed on Ubuntu already includes the UNO bindings, there is no need to use a special OpenOffice version of Python to do the job, the standard one will do. The script takes two arguments, the input file and the output file, and works out the formats based on the extensions. Doing the bulk convert is therefore extremely easy:

$ ls *.odg | while read f; do
> echo $f
> python DocumentConverter.py $f ${f%.*}.pdf
> done

Job done! It took 5 minutes for my laptop to convert all 42 files, during which time I made coffee rather than repetitively click on UI buttons and I even have enough time left to blog about it. Oh and I have a happy customer: that's the most important.

Negative Unread Messages

Here's what LinkedIn had to say about my message summary today:

So I have a negative number of unread messages... Does it mean I've got to unread one of them to bring the counter back to zero?

Installing OpenERP on Ubuntu 10.04 LTS

Background

It's that time of the year again. I need to prepare all the information required by my accountant to issue my company accounts. Luckily I have most of it saved in a handy directory on my laptop, with a backup copy on the server. However, it still takes a lot of time that I'd rather be spending doing something else. Accounts are not the only process that I'd like to improve: sales, expenses, invoicing, everything that is not part of my daily job is done in an ad-hoc way. This is exactly what ERP systems are designed to address. And as usual, there is an open source solution out there, one that is even fully supported on Ubuntu: OpenERP. Let's install it then!

Before we start, OpenERP is a client-server solution and as such there are two components to consider:

OpenERP Server

This is a central component that is deployed on a central server and is responsible for managing the company database. You should have a single instance of it for the whole company.

OpenERP Client

This is a desktop application that enables users to view and update the data held in the server. It should be installed on every computer that needs access to the ERP system.

In addition, OpenERP also offers another server component called OpenERP Web. This component is meant to be deployed on the same server as OpenERP Server and offers a web interface to the ERP system, meaning that you can access the system using a vanilla web browser, rather than the dedicated client application. This is great if you have a large number of users and don't want to deploy the dedicated client everywhere. I will ignore this component for today and only go through the installation of the server and dedicated client.

OpenERP Server

To install the server component, you need a computer that will act as a server. You could potentially install it on your desktop or laptop if you are sure that you will only ever be the single user of the application but I wouldn't recommend it. In my case, I decided to install it on my existing home server that runs Ubuntu Server 10.04 LTS.

Install PostgreSQL

OpenERP needs a database engine and is designed to run with PostgreSQL so we need to install this first. To do this, connect to the server and just install the relevant package, as detailed in the OpenERP manual:

$ sudo apt-get install postgresql

Create an openerp user in PostgreSQL

The server will need a dedicated user in the database so we need to create it. To do this, we first need to start a session under the identity of the postgres Linux user. We can then create the database user that we will name openerp. When prompted, enter a password and make sure you remember it. There is no need for that user to be an administrator so we answer n when asked that question. Then close the postgres session to come back to your standard Linux user.

$ sudo su - postgres
$ createuser --createdb --username postgres --no-createrole \
 --pwprompt openerp
Enter password for new role: 
Enter it again: 
Shall the new role be a superuser? (y/n) n
$ exit

Now that this new user is created, let's try to connect to the database engine using it:

$ psql -U openerp -W
psql: FATAL:  Ident authentication failed for user "openerp"

It doesn't work. This is because PostgreSQL uses IDENT-based authentication rather than password-based authentication. To solve this, edit the client authentication configuration file:

$ sudo vi /etc/postgresql/8.4/main/pg_hba.conf

Find the line that reads:

local all all ident

Replace the word ident with md5:

local all all md5

And restart the database server:

$ sudo /etc/init.d/postgresql-8.4 restart

Let's try again:

$ psql -U openerp -W
psql: FATAL:  database "openerp" does not exist

OK, that's a different error which is due to the fact that PostgreSQL tries to connect to a database that has the same name as the user if none is specified. So let's try to connect to the postgres database, which is contains system information and is always installed.

$ psql -d postgres -U openerp -W
psql (8.4.4)
Type "help" for help.
postgres=>

That works so we know that the user has been successfully created and there should be no problem connecting with that user identity.

Install OpenERP Server

OpenERP Server is part of the Ubuntu repositories so it's extremely easy to install:

$ sudo apt-get install openerp-server

Now is a good time for a coffee break. On my installation, the openerp-server package triggers the installation of no less than 108 packages in 48.9MB of archives that will require an additional 251MB of disk space. This may take some time. Most of the additional packages are Python packages, which is sensible because OpenERP is written in Python but the fact that it also requires things like xterm and bits of GTK makes me think that the dependency list could be pruned somewhat. At the end of the installation, a message appears saying that you should go and read the file called /usr/share/doc/openerp-server/README.Debian. Go and do this. It mainly explains the PostgreSQL installation that we just did but it also mentions a bit of useful information, namely that the OpenERP Server configuration file is /etc/openerp-server.conf. That's quite handy because we need to update it.

$ sudo vi /etc/openerp-server.conf

If you are installing the server and client on different machine, which I would recommend, you need to find the line that says:

interface = localhost

And replace the word localhost with the IP address of your server. If you don't know the IP address of the server, just run ifconfig with no parameters and look for the words inet addr: at the beginning of the second line of output: the IP address is the set of four number separated by dots that come just after that. You then need to modify another two lines:

dbpassword = the password you chose for the openerp user
dbhost = localhost

In theory you shouldn't have to specify dbhost = localhost because leaving that entry blank should default to the value localhost but when I tried this, OpenERP Server could not connect to PostgreSQL. It's now time to restart the server process but before we do this, it's always good to be able to follow the logs in a second window just in case something goes wrong. The location of the log file is helpfully specified in the configuration file that we just edited. Open another terminal, connect to the server and run the following command:

$ tail -f /var/log/openerp-server.log

The last 10 lines of log will appear and every time a new entry is added to the log file, it will also appear in this window. In the first window, we can restart the server:

$ sudo /etc/init.d/openerp-server restart

If all goes well, no nasty error message should appear in the log window.

OpenERP Client

Now, to install the client software on a desktop, connect to the desktop, open a terminal and install the package:

$ sudo apt-get install openerp-client

That's it. Once finished, you will find an OpenERP Client entry in the Applications -> Internet menu. Click on it to open the client. If you want to fill in the feedback form, do so, otherwise click Cancel. You then need to create a new database. To do this, go to the File -> Databases -> New Database menu:

New Database menu

This will open a dialogue where you can enter the details of the new database.

New Database dialogue

You will need to click on the Change button at the top to specify the name or IP address of the server. The port should be the default, 8070. Of course, if you have a firewall between the client and the server, the firewall configuration will need to be updated to allow traffic to the server through this port. The default password for the super administrator is admin as specified in the dialogue. Note that the database name cannot contain spaces, dashes or any non-alphanumeric characters.

So that's OpenERP installed. It's now time to read the rest of the documentation and get a copy of Accounting for Dummies to understand what it's all about.

Backup and Restore a Subversion Repository

Sometimes, you just have to do serious maintenance to a server, like install a new instance of your operating system from scratch with a new partition layout. If this server happens to be your Subversion server, you need to backup your repository and restore it once you're done with the maintenance. Or maybe you just want to move your repository from one server to another. Here's how to do it. The commands below need to be performed on the SVN server by a user who has write access to the repository (in theory any SVN admnistrator).

First, here's how back up the repository to a compressed file:

$ svnadmin dump /path/to/repo | gzip > backup.gz

And how to restore it:

$ gunzip -c backup.gz | svnadmin load /path/to/repo

Those commands are meant for UNIX or Linux so you will have to adapt them if you are running Windows. It shouldn't be too difficult to do so, especially if you are using Cygwin.

Shared Folders in Ubuntu with setgid and ACL

Introduction

There is an often requested feature on Linux (or UNIX) to have the ability to create shared directories similar to what is possible in Windows, that is a directory in which every person who has been given access can read, write or modify files. However, because Linux file systems such as ext4 enforce file permissions that are stricter than any of the windows file systems such as FAT or NTFS, creating such a directory is not obvious. Of course, if you put your shared directory on a FAT or NTFS partition, it will automatically behave just like in Windows but that requires a separate partition and doesn't allow you to enforce permissions on a per-group basis. So here's a quick guide on how to do this with Ubuntu. The same principles apply to other Linux distributions so should be portable.

Use Cases

Let's go through a couple of classic use cases first, to identify exactly what we want to do.

Project Folder

In a company or university setting where users are assigned to project teams or departments, it can be useful to create shared folders where all members of the team can drop files that are useful for the whole team. They need to be able to create, update, delete files, all in the same folder. They also need to be able to read, update or delete files created by other members of the team. However, users external to the team should only have read access.

Web Development

For anybody doing web development on Linux, a classic problem is when you have to deal with development or test web servers. The default web server process runs with the www-data user and the document directory is owned by the same user. It would be great if all web developers on the team were able to update the document directory on the server while not requiring root access to do so.

Linux Default Behaviour

Linux has the concept of user groups. You can check what groups your user belongs to by typing the following on the command line:

$ groups
bruno adm dialout cdrom plugdev lpadmin admin sambashare

On a default Linux installation, groups are used to give access to specific features to different users, such as the ability to administer the system or use the CD-ROM drive. But one of the core feature of user groups is to support file permissions. Each file has separate sets of read, write and execute permissions for the user who is the owner of the file, the group that owns the file and others, that is everybody else. Whenever a user attempts to read, write or execute a file, the system will decide whether he can do it based on the following rules:

• if the user is the owner of the file, user permissions apply,
• otherwise, if the user is part of the group that owns the file, group permissions apply,
• otherwise, others permissions apply.

So to configure a shared directory as defined above, we need to:

• create a user group for the team,
• assign all team member users to that user group,
• create a directory and configure it so that all users in the group can:
  • add new files to the directory,
  • modify any existing file in the directory,
• and of course, all this should work without users having to do anything special.

How To

Enable ACL

The first thing we need to do is to enable ACL support on the partition where we will create the shared directory. ACL extend the basic Linux permission implementation to enable more fine grained control. As this requires the file system to be able to store more permission meta-data against files, it needs to be configured accordingly. We can do this by adding the acl option to the relevant line in /etc/fstab, such as:

UUID=b8c490d0-0547-4e1f-b052-7130bacfd936 /home ext4 defaults,acl 0 2

The partition then needs to be re-mounted. If the partition to re-mount is /, /usr or /home, you will probably need to restart the machine. Otherwise, the following commands should re-mount the partition:

$ sudo umount partition
$ sudo mount partition

where partition is the mount point of the partition as defined in /etc/fstab, such as /var/www.

Create Group

We then need to create the group to which we will give shared access, let's call that group teamgroup:

$ sudo groupadd teamgroup

Try to give the group a meaningful name while keeping it short. If it's meant to be a team group, give it the name of the team, such as marketing. Note the following restrictions on Debian and Ubuntu for group names (taken from the man page):

It is usually recommended to only use groupnames that begin with a lower case letter or an underscore, followed by lower case letters, digits, underscores, or dashes. They can end with a dollar sign. In regular expression terms: [a-z_][a-z0-9_-]*[$]?

On Debian, the only constraints are that groupnames must neither start with a dash (-) nor contain a colon (:) or a whitespace (space: , end of line: \n, tabulation: \t, etc.).

Groupnames may only be up to 32 characters long.

We then need to assign users to that group:

$ sudo usermod -a -G teamgroup teamuser

Where teamuser is the login name of the user to assign to the group. This assignment will take effect next time the user logs in. Make sure that you do not forget the -a option otherwise you will wipe out all existing group assignment for that user, rather than just adding a new one.

Create the Folder

The next step is to create the shared folder. This is easy:

$ cd /path/to/parent
$ mkdir teamfolder

Where /path/to/parent is the path to the parent folder and teamfolder is the name of the folder you want to create. We then assign group ownership of the folder to the group previously created:

$ chgrp teamgroup teamfolder

And give write access to the group on that folder:

$ chmod g+w teamfolder

Let's check what this folder looks like:

$ ls -l
drwxrwxr-x 2 teamuser teamgroup 4096 2010-03-03 14:32 teamfolder

Now, let's try to create a new file in that directory:

$ touch teamfolder/test1
$ ls -l teamfolder
-rw-r--r--  1 teamuser teamuser 5129 2010-03-03 14:34 test1

That looks good and any other user who is part of teamgroup should be able to create files in this directory. However, group members will not be able to update files created by other members of the group for the following reasons:

• the group that owns the file is the user's primary group, rather than teamgroup,
• the file's permissions only allow the owner of the file to update it, not the group.

Set the setgid Bit

We'll solve the first problem by setting the setgid bit on the folder. Setting this permission means that all files created in the folder will inherit the group of the folder rather than the primary group of the user who creates the file.

$ chmod g+s teamfolder
$ ls -l
drwxrwsr-x 2 teamuser teamgroup 4096 2010-03-03 14:32 folder

Note the s in the group permissions instead of the x that was there previously. So now let's try to create another test file.

$ touch teamfolder/test2
$ ls -l teamfolder
-rw-r--r--  1 teamuser teamuser  5129 2010-03-03 14:34 test1
-rw-r--r--  1 teamuser teamgroup 5129 2010-03-03 14:35 test2

So now whenever a file is created in the team directory, it inherits the team's group.

Set Default ACL

The second issue is related to umask, the default mask applied when creating files and directories. By default umask is set to the octal value 0022, as demonstrated if you run the following:

$ umask
0022

This is a negative mask that is applied to the octal permission value of every file or directory created by the user. By default, a file is created with permissions rw-rw-rw-, equivalent to 0666 in octal and a directory is created with permissions rwxrwxrwx, equivalent to 0777 in octal. umask is then subtracted from that default to give the effective permission with which files and directories are created. So for a file, 0666-0022 gives 0644, equivalent to rw-r--r-- and for a directory 0777-0022 gives 0755, equivalent to rwxr-xr-x. This default is sensible for most situations but needs to be overriden for a team directory. The way to do this is to assign specific ACL entries to the team directory. The first thing to do is to install the acl package to obtain the necessary command line tools. Well, in fact, the first thing to do would be to enable acl on the relevant partition but we already did that at the very beginning.

$ sudo apt-get install acl

Now that the package is installed, we have access to the setfacl and getfacl commands. The first one sets ACLs, the second one reads them. In this particular case, we need to set default ACLs on the team folder so that those ACLs are applied to files created inside the directory rather than the directory itself. The syntax is a bit complicated: the -d option specifies that we want to impact the default ACLs, while the -m option specifies that we want to modify the ACLs and expects an ACL specification to follow.

$ setfacl -d -m u::rwx,g::rwx,o::r-x teamfolder
$ touch teamfolder/test3
-rw-r--r--  1 teamuser teamuser  5129 2010-03-03 14:34 test1
-rw-r--r--  1 teamuser teamgroup 5129 2010-03-03 14:35 test2
-rw-rw-r--  1 teamuser teamgroup 5129 2010-03-03 14:36 test3

There we go, it all works as expected: new files created in the team folder are created with the team's group and are group writeable. To finish off, let's have a look at how the folder's ACLs are stored:

$ getfacl teamfolder
# file: teamfolder
# owner: teamuser
# group: teamgroup
user::rwx
group::rwx
other::r-x
default:user:rwx
default:group:rwx
default:other:r-x

Granting and Revoking Access

Granting a user write access to the team folder is now extremely easy: you can just add that user from the team's group when he joins the team:

$ sudo usermod -a -G teamgroup joiner

Where joiner is the user ID of the user joining the team. Revoking access is nearly as easy, you just need to remove the user from the team's group. Unfortunately, there is no way to do this in a simple command so you will have to edit the file /etc/group, find the group and remove the user ID from that group.

Variations

Restrict Delete and Rename to Owner

By default, any user who has write access to a file can delete or rename it. This means that any member of the team can delete or rename any file created by another member. This is generally OK but if it is not, it can also be restricted by setting the sticky bit on the directory:

$ chmod +t teamfolder
$ ls -l
drwxrwsr-t 2 teamuser teamgroup 4096 2010-03-03 14:32

This feature is used on the /tmp directory to ensure that all files created in that directory can only be deleted by their owners.

Restrict Access for Others

Another variation that may be more useful is to completely deny access for users that are not part of the team. it may be that a particular team is working on some sensitive stuff and you don't want anybody outside the team to see it. To do this, we just revoke all permissions and ACLs for others on the team folder:

$ chmod o-rx teamfolder
$ setfacl -d -m o::--- teamfolder

References

• Howto: Linux Add User To Group
• Using ACLs with Fedora Core 2
• setuid (and setgid) on Wikipedia
• Sticky bit on Wikipedia

Ubuntu Lucid Netbook Remix from Alternate CD

The Problem

I've had Ubuntu Netbook Remix running on my Asus EeePC 701 for some time. After upgrading my main laptop to the beta 2 of Ubuntu Lucid 10.04, I wanted to do the same to the EeePC so that I could test the new release, report bugs if I found any and generally benefit from the improvements in 10.04.

The first problem I faced was that the EeePC 701 I have only has 4GB of internal storage, which is just enough for Ubuntu but too little to enable me to do a straight upgrade from the previous version (Karmic 9.10). No problem, I thought, I can re-install from scratch as I really have nothing important on that machine.

I created a flash drive image from the UNR CD, as detailed on the Ubuntu web site, booted my EeePC from it and selected to install Ubuntu on the system. However, I then faced another problem related to the limitations of the 701 model: this model has a 7-inch screen with a resolution of 800x480 pixels, which is quite small and the Prepare Disk Space screen doesn't fit in that resolution, making it impossible to install. I duly reported the bug and wondered how I could work around that problem.

Installing from the Alternate CD

One of the great thing with Linux is that you always have a lot of options. Ubuntu in particular also comes with an alternate installer, which is text based and designed to work on very constrained hardware. Exactly what I needed!

I downloaded the alternate CD, created a flash drive image from it, booted the EeePC from it and started installing Ubuntu. The installation from the alternate CD is extremely easy and follows exactly the same path as with the standard CD, with the difference that you don't have the flashy graphical user interface. At the end of the installation, I had a perfectly functional Ubuntu system using the standard desktop. However, what I wanted was the netbook desktop.

From Standard to Netbook Desktop

The Ubuntu netbook desktop looks very different from the standard one but in practice it is just made up of a small number of packages.

Adding the Netbook Packages

Adding the netbook packages is extremely easy. Open a terminal and run the following command:

$ sudo apt-get install go-home-applet maximus\
 netbook-launcher window-picker-applet

Adding Launcher and Maximus to Application Startup

Once this is done, you will need to ensure the netbook launcher and maximus applications are started automatically. To do this, go to System -> Startup Applications and add two entries with the following commands:

• netbook-launcher
• maximus

Make sure that both can be started by starting them manually, either in a terminal window or via ALT-F2. Then, disable the desktop to ensure you don't accidentally click on it when you want to start an application:

$ sudo gconftool-2 --type bool\
 --set /apps/nautilus/preferences/show_desktop false

Customising the Gnome Panels

You then need to customise the Gnome panels.

Right click on the top panel, where the Applications menu is and remove it. Do the same with the Firefox and Help icons. Then right-click again, in an empty area, and select "Add to Panel"; add the Go Home Applet, which will add a small Ubuntu icon. Right click on that icon again, select "Move" and move it all the way to the left.

Right click on an empty area of the top panel and select "Add to Panel"; add the Window Picker Applet and move it to the left so that it is flush left against to Go Home Applet.

Finally, right-click on the bottom panel and select "Delete this Panel".

Log out, log back in again and you should have a full netbook desktop that look something like this:

Lucid Netbook Desktop

At first, the favourites folder will be empty so you will have to add them yourself.

Final Changes

One final change I made to the installation is that I removed OpenOffice.org and Evolution. The former because it occupies a lot of hard disk space, the latter because it really doesn't work well on so small a screen.

Other Options

An alternative option to install all the required packages is to install the netbook meta-package:

$ sudo apt-get install ubuntu-netbook

I didn't try this so I don't know how much it installs and configures for you. One of the nice side effect of doing it the way I did is that it keeps some standard configuration, such as the multiple workspaces that you can access via CTRL+ALT+arrow keys. I find that this works particularly well with the netbook interface.

SVG and HTML5 Support in IE9

The Register has an article today about the next version of Microsoft Internet Explorer, IE9. You can already download a preview and apparently it looks nice and has support for SVG and HTML5. At last! I hear you say, only 2 years after the rest of the pack. The reason why I find this very exciting is because of SVG rather than HTML5. This is the type of technology that could be very useful in all sorts of areas where Flash is used today, as demonstrated by Microsoft's business charts and map examples.

So what can you do with SVG that you can't do with Flash? In a nutshell, here is my short list:

• You can style SVG using CSS, the same as HTML so if you want to change the look and feel of your site, you can do text and graphics in one go;
• It is a W3C standard so anybody can provide an implementation and you are not tied to a particular company;
• It is a dialect of XML so anybody with a text editor can create SVG data;
• As a dialect of XML, every tool that manipulates XML and HTML, including web based languages like PHP can manipulate SVG so it is extremely easy to generate on the fly and integrate into a web page;
• You can use AJAX technologies with it the same way you do with HTML.

I'm sure there are others but that's all I can think of at 1:30am. Generally speaking, the huge advantage of SVG is that it can re-use the complete HTML tool chain, which offers a huge variety of tools both open source and commercial.

Fractals with Octave: The Whole Shebang

After all this time writing this simple series of how to create fractals with Octave, I finally got to the end of it and published the code on GitHub so here is a nifty summary.

Articles

Each article has a link to the previous and following ones so you can just start with the first one and follow up to the last one.

• Classic Mandelbrot and Julia
• More on the Classic Sets
• Other Polynomials
• Trigonometric and Exponential Functions
• Burning Ship
• Original Function Studied by Gaston Julia

Code

The code is available on GitHub and can be downloaded from the project page, where you will also find some installation instructions.

If you're interested, please download the code and if you use it to create stunning images, I'd love to hear from you. If you think you can improve the code, don't hesitate to suggest changes or fork it.

References

To quote the project page, none of this was created in a vaccum. I used a number of offline and online references so if you are interested in the subject of fractals, you could do a lot worse than checking them out:

• Fractal Geometry, Mathematical Foundations and Applications, 2nd Edition by Kenneth Falconer;
• Generating Cool Fractals, by Xavier Calbet, in Free Software Magazine;
• The Wikipedia articles on Fractals and The Burning Ship;
• Last but not least, the excellent articles and multiple examples by Paul Bourke.

The Art of Database Analysis, Take 2

Thanks to Ed, I found this interesting post on graphs and decided to adapt it to my previous database graph. So I now have a version of that script that uses the pygraph library:

Database PyGraph

I like this one better, it looks a lot more organic.