Each PDF document contains a complete description of the document, including images, text, vector graphics, raster images, and may contain the necessary fonts to display text. To view PDF documents you need to have certain computer programs, which are free and can be found via the Internet.

PDF files can be used on most platforms, Linux is also included. The free Adobe Reader is the PDF-leader and allows Linux users to read any PDF files, but we have reviewed some alternative viewers you can use to open PDF files in Linux. Here’s the list of 5 most used:

1. Adobe Reader – freeware for Linux.
2. Evince – the default PDF viewer for GNOME.
3. Xpdf for the X Window System.
4. KPDF for the K Desktop Environment.
5. Foxit Reader by Foxit Software.

Adobe Reader

The Adobe Reader (aka Acrobat Reader) is available as a no-charge download from Adobe’s web site, and allows viewing & printing any PDF files. The new Adobe Reader 9.1.3 (for Linux) doesn’t have any critical security vulnerabilities while providing more stability. The update is available as a full Adobe Reader 9.1.3 installer and can be downloaded from the Adobe FTP server. This multilingual update is available in the following language versions: English, French, German, and Japanese.

System requirements:
-32-bit Intel Pentium processor or equivalent
-Red Hat® Linux WS 5, SUSE® Linux Enterprise Desktop (SLED) 10 SP2 or Ubuntu 7.10
-GNOME or KDE Desktop Environment
-512MB of RAM (1GB recommended)
-150MB of available hard-disk space (additional 75MB required for all supported font packs)
-GTK+ (GIMP Toolkit) user interface library, version 2.6 or later
-Firefox 2.0 or later
-OpenLDAP and CUPS libraries

This is the most popular PDF viewer, but there are some alternative viewers and you are welcome to try them too.

Evince

Evince is a document viewer for multiple document formats as pdf, postscript, djvu, tiff and dvi. The goal of evince is to replace the multiple document viewers that exist on the GNOME Desktop with a single simple application. Evince has ben included by GNOME since GNOME 2.12 was released. It is written mainly in C and C++. It has been released under the GNU General Public License, so Evince is free software. It’s not just a PDF viewer, and it’s doing the job very well.

Features:
-Search – Integrated search displaying the number of results found and highlights the results on the page.
-Page Thumbnails – Thumbnails of pages show quick reference for where you’d like to go in a document.
-Document Printing – Using the GNOME/GTK printing framework Evince can print any document it can open.
-Encrypted Document Viewing – Evince can open PDF documents that have been encrypted.

Xpdf

Xpdf is an open source PDF viewer for the X Window System and runs on UNIX, VMS, and OS/2. The non-X components (pdftops, pdftotext, etc.) also run on Win32 systems. Xpdf includes programs which extract images from PDF files or convert PDF to PostScript or text, so it’s not a somple PDF viewer. These programs run on DOS, Windows, Linux and Unix.

It also has been licensed under the GNU General Public License. You can see the Xpdf web page for download  links. Source code, precompiled binaries and language support packages of the current version Xpdf 3.02pl3 are available for Linux, Spartac and DOS/Win32.

KPDF

KPDF is a PDF viewer, based on xpdf for KDE (K Desktop Environment). Same as original Acrobat Reader, it provides side panel with thumbnails, allows double page mode. The TTS (text-to-speech) of PDF documents is also included.

The latest version KPDF 0.5.10. was released on August 26, 2008 and has some interesting features like: three different ways of searching, put fonts used by the document on the properties dialog, support for images with alpha channel, Google-like search on thumbnails, cursor wrapping over screen for continous scrolling, save zoom setting on exit and many others.

Foxit Reader

Foxit Reader is a multilingual PDF reader created by Foxit Software. It is available as freeware but has also a full version with enhanced functionality. As a small and fast PDF viewer, Foxit Reader currently has over 50 million users all around the world. After keeping users waiting for almost two months, Foxit Reader 3.1 has been released and it introduces many fascinating new features including internet search and favorite toolbar settings.

Foxit Reader 3.1 supports internet keyword search. You can select the text and click the pop-up search icon or press and drag the mouse directly to search for the related information in Internet. It also supports customization of toolsappearing in the Favorite Toolbar area, so that users can choose the tools that are used most often easily and quickly. You are welcome to look at the official website for more features.

So you shouldn’t have any problems viewing PDF files in Linux; we have recently reviewed the possibility of viewing doc files in linux and there were no problems too. We are going to check some other popular file formats in the near future, so if you would like to see any specific formats, please, let us know. You are welcome to add comments to this article so we could know what are your areas of interest.

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What are the network interfaces? They represent devices that are used to transmit and receive packages of data. The examples of network interface devices are: Ethernet card, ISDN adapter, modem and etc. You can imagine that a network interface is a mailbox or an end of pipe, where you can send information and receive an answer. The integral attribute of network interface is address.

Generally users encounter with IP (Internet Protocol) networks. In the given review we are going to consider IPv4 (4th version of IP addresses), which are still very popular among the end users. After that we will discuss how to setup a network connection in Linux, taking as an example Ethernet card (which presents an interface allowing to connect a PC to the net with the help of copper twisted pair cable with the data transfer speed of up to 1GB/s). You can setup other interfaces in a similar way. To setup the interface in Linux the following steps should be completed:

• Physical installation of the card in the system (we suppose you’ve already done this step or the interface is in the motherboard of your computer; moreover don’t forget to plug in the cable as well)
• Installation of the proper drivers, so Linux can work with your card
• Specifying IP address and some other parameters, which are needed for IP network

In Linux OS network interfaces (as the majority of other devices) are set up with the help of text files, which can vary depending on distributions, for example:

We are going to review it by Ubuntu example.

All Linux network interfaces have unique alphanumeric identifiers. For Ethernet interfaces the identifier consists of “Eth” prefix and interface ordinal number, which is generally assigned by OS depending on the order of devices on PCI bus; however in some cases it can be changed. Linux can work (and, of course, assign an identifier) just with those devices, which have proper drivers installed. Run ifconfig command in the terminal. In case you see your network card in the list, it means that Linux installed the drivers. Here is the way a response you should get may look:

As you probably understood “eth0″ means your network card. In case there are some network cards, for each one there will be an eth section with the order number.

Using dmesg | grep -i eth command you can specify the name of network interface that corresponds to your network card. Of course, it can be useful just in case you have several cards. Here is the way it looks:

If you don’t see the card you need in the list, you will have to find and install the driver.

A driver is a small program that allows operating system to get the functionality of certain devices. Due to this fact the drivers for different operating systems differ from each other (still there are some exceptions, for instance, some drivers for Windows can be used in Linux as well).

In Linux drivers are implemented in the kernel by compilation or by installing special kernel module. Drivers are generally distributed in the same way as usual programs (in particular in the form of source code), but their installation may require some additional actions, thus it’s strongly recommended to get familiar with the README for a certain driver. The most probable sources for proper drivers are:

• Webiste of device manufacturer
• Website of your Linux distribution provider (in particular, update packages for Ubuntu, which include drivers, appear on a regular basis – drivers for some network cards you can find in the package linux-backports-modules-intrepid-generic).
• Hackers or communities websites

The process of configuring network interface for working in IP networks includes defining the following parameters:

IP address of interface.  It represents 4 decimal numbers that are separated by periods. For example, 10.9.8.7. In case you connect your computer to an existing network, the address should be taken from network administrator; but if you create your own network, it’s recommended to choose IP address from special range: 10.0.0.0-10.255.255.255, 172.16.0.0-172.31.255.255 and 192.168.0.0-192.168.255.255

Subnet mask (address mask). Given parameter is used to define the multitude of computer addresses, which are available in your network. If there is a necessity you can learn more here. In small networks the most common mask value is 255.255.255.0.

Gateway. If your network is going to have connection with other network (even with Internet), you need to define the address of routing computer (gateway), which is directly connected both with your network and the other one. All the data packages that are not masked by the above mentioned mask will be transferred to this router for redirection to the extranet.

Broadcast address. It’s used to send the data to all computers in your network at once. In most cases there is no need to specify it because the system can automatically calculate it.

DNS server address. It represents IP address of a server that transforms character names, which are convenient for users (for example, www.lampdocs.com, www.linux.com and etc), into appropriate IP addresses and vice versa. Generally such a server is maintained by your internet provider, moreover very often several servers are provided to ensure fault tolerance.

If the user wants to get rid of setting all the parameters, a special server can be created in the network – DHCP (Dynamic Host Configuration Protocol), which will automatically configure your network interface. Get in contact with the administrator of your network or your Internet provider to find out if there is a DHCP server. In case such a server doesn’t exist, you will need to specify all the settings manually; it’s not as hard to do and the procedure is almost the same as the one in Windows. Now we are going to show how you can do that in Ubuntu.

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Opera Unite Services are based on the same standards as the Web sites. It simplifies the creation of new applications, based on Opera Unite. Opera Unite technology is available in a special version of Opera browser 10, which is available for free download at Opera Labs.
The Opera Unite Services works right in your browser. This time users have the following free services:

• File Sharing. With this application you can grant access to files on your computer to other users. In this case, don’t need to pre-load these files to the specialized online services. You must select on your local disk folder, and Opera Unite generate a direct link to this folder.
• Web Server. This service allows you to run a website from your computer. Just choose to local disk folder with the files the web site and allow access to it from outside.
• Media Player. Media player provides access to the music of the user wherever they are located and from any computer. Just choose the folder with the music collection in MP3 format and allow access to it. You can open the direct link of Opera Unite in any browser.
• Photo Sharing. Now you can share photos directly from your computer without sending the files to online services. You must select the folder of photos on a local disk, and the application form a gallery of thumbnails. Full photos are downloaded by clicking on the thumbnail.
• The Lounge. With this service you can organize chat with your friends right on your computer. Friends may join the conversation by clicking on the link directly, without having to register with any online service. Depending on the plants, just tell them the password to enter the chat room.
• The Fridge. This service makes it possible to attach a note to the virtual refrigerators friends. You can exchange messages with them in safe mode and in real time.

Here is the screenshot of this page:

This service will allow easy file sharing for users without experience. Also there is nothing to install and remote access can be set up with any operating system. That’s another great tool from Opera Software: I like their browser and of course, Opera Mini…

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