Enter, the Arduino: a low-cost, open source, tiny hardware board for connecting the real world to your computer, and/or to the whole internet. What can be done with it? Everything. The limit is the imagination, and as you’ll see from a few of the example creations we review here, imaginative use is the norm.

Open hardware
Just as GNU/Linux software spread because everyone owned it, and could improve it, giving people the confidence to get involved, so with open hardware. The reference designs for Arduino are distributed under a Creative Commons licence (the software is GPL/LGPL, naturally), and the Italian company behind the boards, Smart Projects, is keen to welcome new contributors and variants. Boards are manufactured in different formats, sold all over the world, and the web is full of different designs if you want to build one yourself, whatever your skill level.
Numbers of boards in use are estimated in the hundreds of thousands, though like Linux distros, the freely copiable nature makes an accurate count difficult. What’s not difficult to see is the genuinely open nature of the online communities, and hackspace meetings, around Arduino projects. This has led to a cornucopia of wonderful projects from diverse artistic and creative people – but first, some history…

Those with long memories of geekery and the free software movement will know of the Tech Model Railroad Club (TMRC) – a group of MIT students who got together and played with trains. Some liked the modelling aspect, but the legendary Signals and Power Subcommittee implemented, in the 1950s and 1960s, a semi-automatic control system of great digital cunning, before acquiring a PDP-11 in 1970. TMRC members embodied early hacker culture, giving it much of its current vocabulary and terms of reference, and many became leading lights in DEC and other early computer companies, but this hacker culture fitted the American stereotype of the nerd, the socially awkward genius who could never get the girl (TMRC was, inevitably, an all-male club).

The hacker and free software movement has always suffered from an image problem – such that as female participation in professional IT has declined from 50% to 20% in the last 50 years, some free software projects have a derisory 1% female participation. It’s pathetic, boys, really – but there are signs of hope.

There’s more on page two…

With the right attitude, and some tips and tricks from industry experts, you can soon turn your homegrown Android app into a nice little earner. Adrian Bridgwater explains how…

Advisor:
Adrian Bridgwater
Adrian has been a technology journalist and IT communications consultant for nearly two decades. His journalistic creed is to bring forward-thinking, impartial, technology editorial to a professional and hobbyist software audience around the world.

There’s a fantastic book by former Intel CEO Andy Grove called Only The Paranoid Survive, which is themed around the turning points in the technology roadmap that led Intel to switch its business model and become the microprocessor giant that we know so well today. These ‘strategic inflexion points’, as Grove called them, were the points at which the paranoid business brain would realise the need for change and the opportunity to make money.

With the world of open source in mind, there comes a time in every developer’s life when however fulfilled they are as a result of working on their homegrown hobbyist projects, the allure of cold hard cash just can not be ignored any longer. Almost every open source project has an arm connected to a potential commercial channel where money can be made; and hey, even Sun Microsystems eventually had to “hand the stewardship” (as they carefully put it) of the Java language over to Oracle.

Commercial reality-check
So with these commercial realities under our belt, let us turn our focus to the Android mobile operating system, which of course runs on the Linux kernel. Initially developed by Android Inc and later bought by Google, Android now sits under the watchful stewardship of the Open Handset Alliance. Since the wraps came off the initial Android distribution back in late 2007, the operating system now sits with most of its code under the free and open source Apache License.

But enough of the basics, as most of you will know this preamble. When it comes to Android, the question remains: just when should you start to be paranoid and how and when can you expect to start making money from it? You’ve built your Android-based application and now you want to know how you should set about turning it into a revenue stream, right?
One of the problems is that developers face inherent platform fragmentation issues when launching new mobile content and services to the wider market. Companies such as Mobile Distillery produce technology that claims to reduce porting cycles by up to 80% as well as achieving cost savings by giving developers the chance to bring their mobile applications faster to market across more mobile devices.

Not so strange BREW
Having already simplified the porting process for mobile apps to native BREW (Binary Runtime Environment for Wireless), Windows Mobile and BlackBerry, Mobile Distillery says that it recognised the rise of Android and launched its Celsius Android solution to optimise and port applications to Android phones.
“We recognised that Android is becoming a platform of choice for mobile application developers and end users and wanted to lend our expertise to Android applications and so developed Celsius Android,” explains Vincent Berge, the co-founder and CEO of Mobile Distillery.
“Using Celsius, all aspects of mobile application development are optimised and, most importantly, porting cycles are faster. This in turn reduces the time to market of new mobile applications on any Android phone. The launch of Android offers many possibilities for the mobile market and with Celsius we want to help overcome any fragmentation issues so that the developer can be more powerful across all platforms and all phones,” adds Berge.
But of course optimisation and porting process improvements are only just part of the total equation. This is a complex cutting-edge segment of the application development market, after all; with so many impacting factors to juggle, surely a healthy level of paranoia and a wide-angle view are the most prudent tactics to adopt? Android proponents argue that the comparatively new application rankings capabilities are bringing the required commercial touch to the party.

Advisor: Swayam Prakasha

A log file grows without limits unless some action is taken. Growing log files pose many problems since larger files are very difficult to manipulate and file systems can run out of space. Thus there is a need for a solution to prevent the log files from growing beyond a certain size…

Most Linux systems come with a tool called ‘logrotate’ and it is very handy in many situations. It will help the easy administration of systems that usually generate a large number of log files. Using this tool, we can rotate the log files, compress the log files, remove the log files, mail the log files etc. Rotating a log file means taking a copy to a back-up file and creating a new log file. We can then remove the back-up logs when they are out of date. We do not have to have any special privileges to run this logrotate. It is usually installed to run nightly as a cron job. For each service we install, we need to have a configuration file which tells logrotate how to rotate the log files for that specific program. In simple words, logrotate involves regular (typically nightly or weekly) moving of an existing log file to some other file name and then starting afresh with an empty log file. A part of a typical logrotate configuration file is given below.

# see “man logrotate” for details
# rotate log files weekly
weekly

# keep 4 weeks worth of backlogs
rotate 4

# create new (empty) log files after rotating old ones
create

# uncomment this if you want your log files compressed
#compress

The beauty of the logrotate tool lies in the fact that it allows us to handle each log file daily, weekly, monthly or whenever it grows too large. With logrotate, one can keep logs longer with less disk space.
The practice is to run logrotate as a daily cron job. Thus it is not needed to modify a log file several times in any day. If we have a program that keeps a log file and if that log files grows with each passing day, then logrotate can help up in cleaning it up for you. When called, logrotate reads the following two files:
a. The logrotate configuration file /etc/logrotate.conf.
b. The files in the logrotate configuration directory – /etc/logrotate.d. Note that most of the services (Apache web server, MySQL etc) installed on your system create a configuration file in /etc/logrotate.d.

The logrotate can be executed with many command line arguments. If no command line arguments are given, then logrotate will print version and copyright information along with a short usage summary. If it encounters any errors while rotating logs, it will exit with a non-zero status. Logrotate comes with many command line options and some of these are pretty useful. The following are some of the popular used options with logrotate:

-v – Turn the verbose mode on.
-d – Debug mode is enabled.
-f – Forcibly rotate the log files, even if it is not necessary.
– usage – This option prints a short message, giving information on its usage.

Configuration file format
The format of the log rotate configuration file is defined by the manpage for
logrotate. In a nutshell, the format is
as follows:
<global configuration options>
<definition for logfile 1>
<definition for logfile 2>
<definition for logfile 3>

As mentioned earlier, logrotate comes with a default configuration files and it is ‘logrorate.conf’ located at /etc. It is a normal practice to place the service-specific configuration files in the /etc/logrotate.d directory.

Now let’s see how we can use logrotate for rotating the log files…

1. Running Python scripts
On most of the UNIX systems, you can run Python scripts from the command line like so:

$ python mypyprog.py

2. Running Python programs from Python interpreter
The Python interactive interpreter makes it easy to try your first steps in programming and using all Python commands. You just issue each command at the command prompt, one by one, and the answer is immediate.
Python interpreter can be started by issuing the command:

$ python
kunal@ubuntu:~$ python
Python 2.6.2 (release26-maint, Apr 19 2009, 01:56:41)
[GCC 4.3.3] on linux2
Type “help”, “copyright”, “credits” or “license” for more information.
>>> <type commands here>

In this article, all the code starting at the  >>> symbol is meant to be given at the
Python prompt. It is also important to remember that Python takes tabs very seriously – so if you are receiving any error that mentions tabs, correct the tab spacing.

3. Dynamic typing
In Java, C++, and other statically typed languages, you must specify the data type of the function return value and each function argument. On the other hand, Python is a dynamically typed language. In Python you never have to explicitly specify the data type of anything. Based on what value you assign, Python will keep track of the data type internally.

4. Python statements
Python uses carriage returns to separate statements, and a colon and indentation to separate code blocks. Most of the compiled programming languages, such as C and C++, use semicolons to separate statements and curly brackets to separate code blocks.

5.  == and = operators
Python uses ‘==’ for comparison and ‘=’ for assignment. Python does not support inline assignment, so there’s no chance of accidentally assigning the value when you actually want to compare it.

Advisor:
Swayam Prakasha

Everyone understands how critical TCP/IP (Transmission Control Protocol / Internet Protocol) is, but fails to realise the fact that the TCP/IP suite relies on many functions provided by ICMP (Internet Control Message Protocol). ICMP is one of the core protocols of the IP suite. It a network-layer protocol that is primarily concerned with routing issues.

With the help of this protocol, routers are able to send error or control information to their hosts. This protocol is of great help for system administrators, as it aids in testing for the connectivity and searching for the configuration errors in a network. Let us see an example of how ICMP facilitates this. When a router is not able to forward a datagram, it informs the original source about this error, and does not specify what action needs to be taken to overcome the error. It is up to the source to take the necessary action in order to correct the problem. It is important to notice here that ICMP cannot be used to inform the intermediate routers when a problem occurs. This is basically because a datagram contains fields that specify the original source and the ultimate destination. So when a router gets a datagram, it does not know the path taken by the datagram to arrive there. Instead of discarding a datagram when an error occurs, it informs the source from which the datagram originated. Hence the connectivity and configuration of a network is easily tested.

ICMP is a classic example of a client-server application. The fundamental purpose of this protocol is to report problems with the delivery of IP datagrams. The protocol is also frequently used by internet managers to verify correct operations of End Systems (ES) and to check that routers are correctly routing packets to the specified destination address. It is the responsibility of the network-layer protocol to ensure that the ICMP message is sent to the correct destination. This is achieved by setting the destination address of the IP packet carrying the ICMP message. The source address is set to the address of the computer that generated the IP packet (carried in the IP source address field) and the IP protocol type is set to ‘ICMP’ to indicate that the packet is to be handled by the remote end system’s ICMP client interface.

Functions provided by ICMP
The following are some of the functions provided by this protocol:

1. Announce network errors
Such as a host or entire portion of the network being unreachable, due to some type of failure. A TCP or UDP packet directed at a port number with no receiver attached is also reported via ICMP.

2. Announce network congestion
When a router begins buffering too many packets, due to an inability to transmit them as fast as they are being received, it will generate ICMP source quench messages. Directed at the sender, these messages should cause the rate of packet transmission to be slowed. Of course, generating too many source quench messages would cause even more network congestion, so they are used sparingly.

3. Assisting in troubleshooting
ICMP supports an echo function, which just sends a packet on a round trip between two hosts. Ping, a common network management tool, is based on this feature. Ping will transmit a series of packets, measuring average round-trip times and computing loss percentages.

4. Announcing timeouts
If an IP packet’s TTL (time to live) field drops to zero, the router discarding the packet will often generate an ICMP packet announcing this fact. Traceroute is a tool which maps network routes by sending packets with small TTL values and watching the ICMP timeout announcements.

ICMP messages are sent in various situations. Some of the familiar situations are when a datagram cannot reach the destination, when the gateway can direct the host to send traffic on a shorter route etc. It is important to understand here that the purpose of these control messages is to provide feedback about the problems in the environment. Typically, ICMP messages report errors in the processing
of datagrams.

ICMP packets are handled in the same way as any other data packet. However, ICMP packets do not include source and destination ports. A special signature called ‘type of message’ is included in these packets and this message type indicates the purpose of the ICMP packet. In fact, ICMP is essentially just a collection of predefined messages, each of which provides very specific functionality. It is to be observed here that ICMP packet delivery is unreliable – which means hosts can not count on receiving ICMP messages for any problems happening over a network.

Advisor:
Sukrit Dhandhania

Resources:
Scribus
Little CMS Colour management engine (optional, but recommended)
Adobe Acrobat Reader (optional, but recommended)

If you have worked in the desktop publishing business or used some of the commercial desktop publishing tools such as QuarkXpress or Adobe InDesign, you must know how easy they made your work. They are also quite expensive. Depending upon how deep your pockets run, it is unlikely that too many small organisations and especially individuals can afford these software packages. That’s where Scribus steps in to save the day. Scribus is an open source application for desktop publishing. The Scribus Project was started in 2001 and has gained great popularity, support, and won several awards since its inception. The fact that it is available for just about every operating system is just one of the features that sets it apart from its commercial competitors. Let’s take a look at how to set it up and make it work…

01     Getting Scribus
Scribus is available for several operating systems such as Windows, Mac and Linux. There are a number of ways by which you can get Scribus. You can either download a ready-to-install binary version of a stable release for your operating system, or you can download and compile the latest build, referred to as the ‘nightly build’. It is recommended that you use the second option. Download the latest version you want from here.

02    Installing bleeding edge Scribus the simple way
A simple way of installing Scribus on Linux is using your distro’s package manager. Use YUM for Red Hat Linux or Fedora machines, and apt-get for Ubuntu or Debian. On our Ubuntu machine we ran the command:

# sudo apt-get install scribus

Note that using such a method for installing Scribus will get you a recent stable release, not the cutting edge development version.

03    Installing Scribus the harder way
Note: This method is only for the brave.
The second method consists of downloading the latest development version of the Scribus code and compiling it. First, get the latest code using the following command. In the command shown below we’re getting the latest development version of Scribus 1.3.5:

# svn co svn://scribus.info/Scribus/branches/Version135

Once the download completes, create a directory called builddir and get into it:

# mkdir builddir
# cd builddir

Now you need to run the cmake command and prepare it for installation. Run the following, replacing /home/username/scribusinstall/ with the path of where you want Scribus to
be installed:

# /usr/bin/cmake ../Scribus -DCMAKE_INSTALL_PREFIX:PATH=/home/username/scribusinstall/

The final step is to run a make and then to install Scribus:

# make && make install

If all went well, you should now have Scribus installed and ready for use. In case you encountered problems during any of the commands you issued, or want more options, feel free to go through the Scribus source installation document.

Advisor

Requirements:
Perl 5.005_03
Math::IntervalSearch 1.05
Digest::MD5 2.33
Devel::DProf 19990108
Date::Parse 2.24
RRDtool’s RRDs Perl module
Storable 2.15

Getting the performance-monitoring data for a server can be invaluable for a person handling a production environment. There are a number of ways to collect this information. Once you collect this data it can be quite a challenge to interpret it accurately and can be even more difficult to make alterations to your system configuration based on the data. To do this effectively you need to run several rounds of performance testing and fixing. Sometimes it can be quite helpful to get a reading of your system’s performance so as to know where you stand. We recently covered two tools, Dstat and gnuplot, that together allow you to collect performance monitoring data and plot into performance graphs. In this article we’ll look at another tool – Orca – that both collects performance data and also plots graphs which helps in interpreting the system performance data. The important difference between Orca and Dstat/gnuplot is that, unlike the latter, Orca plots live reports on the fly and allows you to view these ports using your web server, which can be very useful. This allows you to be able to view live performance graphs of your servers pretty much from anywhere in the world.

Orca was written by Dr Blair Zajac, who has received a PhD Caltech in Geophysics. This wonderful tool is a free download and is relatively simple to get going. Once installed and configured properly it reads system performance data and plots the data into graphs such as the one shown here. The graphs are made available to the user in HTML files which can be accessed in your web browser over the network. Orca reads and plots a performance graph for a number of parameters by default. These include memory, CPU, network, disk IO and so on. The Orca project is hosted here. You can download the source code of the project, read some documentation on it and also view the archives of the Orca support mailing list on this website. If you are serious about using Orca, we would encourage you to sign up for the orca-users mailing list here.

On the Orca website, Dr Blair Zajac has a note requesting a donation as a token of appreciation. We would encourage you to do so, particularly if you are using this wonderful tool as part of a commercial venture. He also has an Amazon wish list from which you can buy him something if you like. The tool is quite useful and we’ve found that it can greatly enhance your ability to assess the load on your servers.

Let us now proceed to the installation. We will then make some configuration changes, then set up a cron job so that Orca can provide you with up-to-date information on the state of your server. Note that Orca is a very flexible tool and there are several configuration parameters that we will not cover in this article. We will leave many of these parameters to the default settings. Once you are comfortable with the configuration of Orca, you can tweak it further.

Orca has been written using the Perl scripting language. You need to have Perl 5.005_03 or better installed on your computer. Most modern Linux distributions ship with Perl 5.005_03 or better. Run a quick check to see if you already have perl installed. Run the command ‘# perl-v’ in terminal window to check. If this command returns with a message like ‘This is perl, v5.8.8 built for i386-linux-thread-multi’, you are good to proceed. If not, check the documentation of your Linux distribution to see how to get Perl installed on your computer. There are also a few Perl modules that Orca requires to function fully. (See the box titled ‘Orca Prerequisites’). The Orca project has been kind enough to bundle these Perl modules along with the source code of the project. You can either download it off the project’s website or find it on the DVD accompanying this issue of Linux User & Developer. You will also need to have a web server if you want to be able to view the reports it generates over the web. Again, most modern distributions of Linux ship with Apache installed by default. If you have landed a machine that does not have Apache, please refer to your distribution’s documentation to see how to get it installed. Without Apache you will not be able to view the Orca reports properly.

]]> http://www.linuxuser.co.uk/features/use-orca-to-monitor-system-performance/feed/ 0 http://www.linuxuser.co.uk/features/publish-and-manage-with-dokuwiki/ http://www.linuxuser.co.uk/features/publish-and-manage-with-dokuwiki/#comments Wed, 23 Dec 2009 07:00:54 +0000 RussellBarnes http://www.linuxuser.co.uk/?p=475 This tutorial will help you to get started with DokuWiki and show you how to extend its functionality with plug-ins…

Advisor:
Dmitri Popov
Dmitri has been writing exclusively about open source software for almost a decade, with a focus on productivity tools and applications.

Resources:
A server with the Apache server and PHP 4.3.3 or higher
The latest stable version of DokuWiki
Tag plug-in
DISQUS plug-in
ODT plug-in
Statistics plug-in
Sync plug-in

DokuWiki has gradually evolved into a powerful and flexible wiki engine suitable for most tasks involving web publishing and collaborative editing. This lightweight and elegant wiki software offers a few nifty features that make it a compelling choice for individual users and work groups alike. DokuWiki doesn’t use a database back-end (all pages are stored as plain text files), which makes it significantly easier to install and maintain a wiki. It provides a flexible mechanism for managing users and their privileges. More importantly, DokuWiki’s default functionality can be extended using plug-ins, and the project’s website features hundreds of modules that can turn your wiki into pretty much anything you like: a blog engine, photo gallery, or database front-end. In other words, no matter what type of content your want to publish on the web, chances are that DokuWiki can handle it with consummate ease.

This article originally appeared in issue 80 of Linux User & Developer magazine. Back issues are still available.

01     Install DokuWiki
Grab the latest release of DokuWiki from the project’s website, unpack the downloaded archive and rename the resulting directory to dokuwiki. Then move the dokuwiki folder into the document root of your Apache server. If you are using XAMPP, the document root is the htdocs directory.

02    Install DokuWiki (continued)
Make the data, conf and lib/plugins directories writable by running the chmod command as root – for example: chmod -R 777 /opt/lampp/htdocs/dokuwiki/data. Point your browser to http://yourserver/dokuwiki/install.php and provide the required information. To make your DokuWiki installation more secure, enable the ACL (Access Control List) feature and grant editing rights only to registered users.

03    Configure DokuWiki settings
Before you start using your wiki, you should configure DokuWiki’s settings. To do that, log in using the username and password you specified during installation, press the Admin button and click on the Configuration Settings link. This opens the Configuration Manager page containing all DokuWiki’s configuration options.

04     Configure basic settings
First of all, you might want to choose the appropriate licence for your wiki’s content. Next, set the Use First Heading For Pagenames option to Always, to force DokuWiki to use the first heading in the text as the page’s title. This might sound like a minor thing, but it greatly improves the overall readability of your wiki.

05    Disable DokuWiki actions
The Disable DokuWiki Actions section lets you disable certain features. For example, if you plan to use your wiki as a conventional content management system, you might want to disable the Old Revisions feature. You can also prevent users from creating accounts in your wiki by disabling the Register function.

06    Modify editing settings
DokuWiki allows you to enable embedding of HTML and PHP code in wiki pages, but you have to enable this functionality manually by ticking the appropriate checkboxes in the Editing Settings section. Keep in mind, though, that according to DokuWiki’s developer, enabling this feature makes your wiki less secure.

07     Tweak advanced settings
The Advanced Settings section allows you to enable and configure several useful settings, including nice URLs which format URLs in a more readable format. You can also enable the 404 error message for non-existing pages, specify the RSS feed format, as well as enable the XML-RPC interface which lets you access your wiki from external applications.

Find out how to create, edit and manage docs using Zimbra Collaboration Suite…

Advisor:
Sukrit Dhandhania
Sukrit is an OpenOffice.org expert but turns his hand to the Zimbra Collaboration Suite for this issue’s in-depth tutorial on managing documents.

Resources:
Zimbra Collaboration Suite

The Zimbra Collaboration Suite (ZCS) is a web-based open source office suite and collaboration platform that works on all operating systems. Paid versions of Zimbra come with extra features and different levels of support. Zimbra provides both the server and client components for users. You can either set up a local Zimbra Collaboration Suite server or sign up with an authorised Zimbra hosting provider. Zimbra Documents is a component of ZCS which allows users to create, edit, share and collaborate over documents with other users. Zimbra Documents is built for sharing and has a WYSIWYG HTML editor built into the web client interface. Let’s look at how to create, manage and share documents using Zimbra Documents…

This article originally appeared in issue 80 of Linux User & Developer magazine.
Back issues are still available here.

Zimbra Collaboration Suite is an open source mashup of Exchange Server and Google Apps which you can install within your office network

01     Logging in and out
The first step to using the Zimbra Collaboration Suite is to get the administrator of your Zimbra setup to create a user account for you. Use the username and password combination to then log into your Zimbra Suite. You will be greeted by a screen that says ‘Loading’ and then you will be taken to the Zimbra Collaboration Suite main interface, which is where all the magic happens.

02    The main window
The main window of Zimbra consists of a number of components. At the top is the search bar. This is a pretty nifty search plug-in with which you can search all the content in your account and then some. In the left sidebar you will have a list of folders, your IM buddy list, Zimlets and the Calendar. Below the search bar you should have a horizontal menu consisting of all the ZCS components, from Mail to the Briefcase.

03    The Zimbra Documents interface
Click on the Documents tab in the ZCS menu. A new tab appears in the left sidebar, called Notebooks. Below the Zimbra main menu is the Documents menu with options allowing you to create a new document, browse or import documents. Below this are the documents contained in the selected Notebook. You’ll see the title of the document, the person who last edited it, the date of the last modification, and the version.

04     Notebooks
Zimbra Documents uses Notebooks, the equivalent of folders. You can have multiple levels of Notebooks, and documents belonging to parent or child Notebooks. To create a new Notebook, click on the New Notebook button above the list of Notebooks in the left sidebar. Enter a name for it and pick a colour. Select an existing Notebook if you want to create a child Notebook. Click OK to create the Notebook.

Adviser

Resources:
All you need for this tutorial is the GanttProject application available from ganttproject.biz

Learn how to monitor your projects with ease using the GanttProject project management tool…

Even the simplest projects can quickly get out of hand if you don’t keep tabs on them. That’s why an application that can help you to deal with various aspects of managing your projects can prove indispensable. There are many open source project management applications out there, but if you are new to the task, GanttProject is a good place to start. It strikes a perfect balance between ease of use and flexibility, offering all the essential features you would expect. As the name suggests, GanttProject is based around so-called Gantt charts (invented by Henry Gantt at the beginning of the 20th Century) to graphically represent each stage of the project and dependencies between them. This visual approach provides an easy way to get an overview of the entire project and its progress.

Click to the next page for step one of our definitive GanttProject tutorial…