Many corporate environments already deploy a published
calendar system with Exchange. From the end-user perspective, it’s simple to
use. From an IT perspective, it’s oftentimes riddled with problems, forcing the
department to baby-sit the Exchange server on a daily (or nightly) basis. As
for the smaller business, it’s just not cost-effective.

What if I told you there is a cost-effective, reliable way
to publish calendars using the Linux platform? Well, there is, and I’m going to
show you how to do it using Firefox, an Apache module, and the Firefox
Lightning plug-in. Here’s how it works.

What’s a published calendar?

A published calendar is a calendar that can be viewed from
a remote location. This enables, for example, on administrator to create and
manage a calendar for, say, an entire company and everyone within the company
would have access to viewing said calendar. This makes life easy when
scheduling such things as company-wide meetings and events.

Getting and installing the
components

Here’s what you need:

  1. Apache Web server
  2. mod_dav
  3. Thunderbird
  4. Lightning

The environment I’m installing on is Fedora Core 6. For
Fedora 7, the installment will be virtually the same. For other distributions,
the installation will need to be modified based on the type of distributions
and the architecture of the hardware.

Typically, with an installation of Linux, the Apache Web
server will be installed. If, however, you have installed a desktop-only
installation, you will need to install Apache as well. This can be done with
the yum installation tool with the yum install httpd command (run
as root). Once this is installed, you will have the /var/www/html
directory, which you will use later.

The next pieces of the puzzle will be installed in
different ways. Let’s get mod_dav installed now. The easiest way to
install mod_dav is with rpm. Get the rpm file from rpmfind.net
and run the command (as root, from the directory the file downloaded into): rpm
-ivh mod_dav-XXX.rpm
where XXX is the release number and
architecture.

Now let’s get Thunderbird and Lightning installed. These
are very straightforward. Download the files Thunderbird
and Lightning.
You must next move Thunderbird to a different directory. Where exactly this is depends
on how you want to manage it. If you have all users on a system to be able to
run Thunderbird, move Thunderbird to the /opt directory. If this is a
system where only a single user works from, you can install Thunderbird into
the users ~/ directory. To be safe, we’ll install into /opt.

Once the Thunderbird file is in /opt, issue the
command tar xvzf thunderbird-XXX.tgz where XXX is the release
number. Now Thunderbird can be started by issuing the /opt/thunderbird/thunderbird
command.

The final installation step will require you to get
through the initial set up of Thunderbird. So go ahead and run through setting
up your mail account. Once that is complete go to the Tools menu and select
Extensions. A new window will open (Figure A) that allows you to install
new extensions. Unlike Firefox, installing extensions in Thunderbird is a bit
different. In Thunderbird, save the extension to your hard drive and press the
Install button (from the Thunderbird extensions window), navigate to the saved
file (the file extension will be .xpi), and press Open; once the count-down
completes, press Install.

Figure A

You can press the Get More
Extensions link to open up a new browser window and find more Thunderbird
extensions.

Now you’re installed, but you’re not quite done.

Configuring Apache’s mod_dav

Open /etc/httpd/conf/httpd.conf (as root) in your
favorite text editor. Scroll to the bottom of the file and add the following
lines:

<Location
/webdav>

Order Allow,Deny

Allow from all

Dav On

 

AuthType Basic

AuthName DAV

AuthUserFile
user.passwd

 

<LimitExcept GET
OPTIONS>

require user admin

</LimitExcept>

</Location>

 

<IfModule
mod_dav_fs.c>

     # Location of the
WebDAV lock database.

     DAVLockDB
/var/lib/dav/lockdb

</IfModule>

 

<Location
/webdav/>

  DAV On

  AuthType Basic

  AuthName "WebDAV
Restricted"

  AuthUserFile
/etc/httpd/passwd/passwords

  require user webdav

</Location>

Now you need to create the webdav
user and a password for that user. Do so with the command:

htpasswd -c
/etc/httpd/passwd/passwords webdav

You will be prompted to enter a password for the user
(twice). This password will be the password users will need to know in order to
gain access to the published calendar.

The final steps will be to create the location that will
house the calendar files. I created /var/www/html/webdav with the
command (run as root):

mkdir /var/www/html/webdav

Make sure the directory was world-readable and writable
with the command:

chmod -R 777
/var/www/html/webdav

Now start (or restart) the Apache server. I tend to start
(or restart) Apache with the command:

/etc/rc.d/init.dhttpd
start

or, in case of a restart:

/etc/rc.d/init.d/httpd
restart

Setting up your calendar

Now it’s time to fire up Thunderbird with the new
Lightning extension. When you start up Thunderbird, the Lightning extension
will exist in the bottom left corner, as shown in Figure B. It’s clean
and takes up little space, yet it remains very usable.

Figure B

Click on any date in the small
calendar to open up the full-sized version in the large right-side window.

There are three tabs in the extension. Press the Calendars
tab to create a new calendar. Press the New button, as shown in Figure C,
to initiate the creation process.

Figure C

From this tab, you can create a new
calendar, edit existing calendars, or delete existing calendars.

The next step is to choose the location of the calendar.
Since we are creating a published calendar, we’re going to select On The
Network. Press Next to continue. The next step is to choose the type of
calendar (I will use iCal) and fill out the location. The location of this
calendar will be hosted on the machine I am working on, so http://localhost/webdav/
will work. For those working on other machines, replace localhost with
the IP address of the machine serving the calendar. Press Next. Now give the
calendar a nickname and select a color to represent the calendar. Press Next.

You will now be asked for the username (webdav) and
the password you used when you created the user above. Enter those and press
OK. Now the new calendar should show up in the calendar listing of the
extension, as shown in Figure D.

Figure D

The new calendar contains the
customizations showing the importance of naming and color selection.

A very simple way to test the calendar’s availability is
to open up a browser on a remote machine and enter the address in the URL bar (in
my case, http://192.168.1.21/webdav/company_calendar.ics). You will be prompted
for the username and password. What will appear (if using an ICS file) will be
a long file (depending upon the amount of entries in the calendar) with text
similar to this:

BEGIN:VCALENDARVERSION:2.0PRODID:-//Mozilla.org/NONSGML Mozilla Calendar V1.1//ENBEGIN:VTIMEZONETZID:/mozilla.org/20070129_1/America/New_YorkX-LIC-LOCATION:America/New_YorkBEGIN:DAYLIGHTTZOFFSETFROM:-0500TZOFFSETTO:-0400TZNAME:EDTDTSTART:19700308T020000RRULE:FREQ=YEARLY;INTERVAL=1;BYDAY=2SU;BYMONTH=3END:DAYLIGHTBEGIN:STANDARDTZOFFSETFROM:-0400TZOFFSETTO:-0500TZNAME:ESTDTSTART:19701101T020000RRULE:FREQ=YEARLY;INTERVAL=1;BYDAY=1SU;BYMONTH=11END:STANDARDEND:VTIMEZONEBEGIN:VEVENTCREATED:20070714T234024ZLAST-MODIFIED:20070715T021150ZDTSTAMP:20070715T021150ZUID:37845adf-0a08-4958-a3d4-a8aed34ba687

Connecting to the calendar

Naturally, this step will differ completely depending on
the type of application you’re using to connect to the remote calendar. Since
we created the calendar with the Thunderbird extension, I am going to show you
how to subscribe to the calendar with KDE’s Kontact. This is a very simple
procedure.

Open up Kontact and press on the Calendar button. Now press
the Add button to begin the process of adding the remote calendar. The first
step is to select the type of calendar you will be creating. Choose Calendar In
Remote File, as seen in Figure E.

Figure E

Kontact allows you to create any
number of calendar types.

Once you select the proper type, press OK to move on. Now
you are going to have to fill in the details of the remote calendar. Figure
F
shows just what you need.

Figure F

Here you can choose settings such as
Read Only and auto-reload/save settings.

Remember, you will need to enter the entire address
(including file name) for the remote calendar. In this case, the address is http://192.168.1.21/webdav/company_calendar.ics.
You also have to select a location for the remote file to be saved to. For
simplicity’s sake, I chose the local users home directory. This can be placed
anywhere, so long as the user has read/write privileges. Press OK and you’re
done. You will be asked for the password of the file and the calendar — named
Company Calendar as per our Kontact settings –will appear in the Kontact
calendar window.

Obviously, the steps for subscribing to this calendar will
vary depending upon what application you use to view it remotely.

Final thoughts

As you can see, deploying a published calendar with Linux
is a fast and easy process. On top of being simple, it’s reliable. And of
course, it’s highly configurable. This setup can be tweaked in numerous ways to
suit your company’s needs. If you want a reliable, cost-effective, publishable
calendar system, this method is it.