Anyone that knows Linux, knows that this operating system, enables so many solutions, and they are part of the 
Linux operating system package. You can gain almost any type of services you need, by either using the built in services on the operating system after the installation (which means they are coming installed within the OS) or by doing a simple update/download and install of new services which are not built in, It is as simple as that.
I will give some examples from the UBUNTU Linux operating system, which is one of my favorite, and it is very simple to use. Installing a service is almost made by using one simple command – called APT-GET (This command goes to find the service you need, download it, and installs it on your Linux system. Mostly it means the service will be installed and running on the system. Sometimes you might need to edit some configuration files, in order to fit it into your network definitions.
The most important issue that you need to remember is that Linux enables you to do anything you want. Linux is being used by many and some prefer to use it and not use the Microsoft Windows Operating System which is so common.
Linux has many operating systems, some are server based (no graphical interface needed) and some are suitable for client side computers/laptops, they do include X-windows which is the graphic interface of a Linux based operating system. Linux has many different graphical interface distributions, which actually means that those distributions are actually a fully functional operating system, with the needed packages of services. Each Linux distribution include different packages, and different GUI interface (which means the graphical side looks a bit different).
The base of them usually works the same, but some of them are based on different Linux Kernel, so the commands are a bit different, and needs to get used to. That is usually why most Linux users get to know one type of a Linux kernel that they get along best with and they stick to that OS and Linux Kernel, on their future Linux experiences.
So let go over some examples of what you can do with the Linux operating system, and how simple things are when defining new services to the system.
Linux Firewall:
Linux has a built in mechanism called IPTABLES, this is a port filtering mechanism, that enables you to set rules for what can pass through the system and what can’t. Firewall rules are mostly port based, any service has its own port, and by defining which ports are allowed and which are not, you can create your own firewall based on that built-in mechanism. All you will need is to place two network card on your Linux, and let the traffic pass through the Linux machine, as it controls the rules of passage. When IPTABLES is empty and no rules are applied, it means anything can go through from outside in, and from the inside out. This option is mostly used by the Linux Server systems.
* Article on how to set a simple Linux Firewall
Another option if you want a graphical management console to define the firewall:
For Linux Desktop – that includes X-Windows (a Graphic interface), you can use the FWBUILDER (Firewall Builder). This tool enables a graphic management interface, that enables you to define the firewall rules, like the tools used on firewall routers (like the CISCO PIX).
* Using fwbuilder to create a Linux firewall
Linux web server:
The Linux web server is mostly based on the APACHE service. Since most application use PHP, and databases, you can use the MYSQL, and of course PHP, so you need to install them as well, and some other tools that can assist you. Below are the basic tools you will need to create a full functional web server, which includes all of the needed services.
- Apache 2 – Linux Web server
- MySQL 5 – MySQL Database Server
- PHP4/5 – PHP Scripting Language
- phpMyAdmin – Web-based database admin software.
- Webalizer – Website Traffic Analyzer
- Mail Server – Postfix (MTA) with Dovecot IMAP/POP3 + Sasl Authentication
- Squirrelmail – A web based email
- VSFTP – A fast ftp server to upload files
- Webmin – A freely available server control panel
- ClamAV – Antivirus software.
- A Firewall using IPtables.
So to summarize, you can do whatever you want to with Linux, just search the internet and see how easy it is.