OS Selection and Configuration
Linux is the kernel that powers many GNU-based operating systems. Sometimes this combination is called GNU/Linux or simply Linux. Because it is free and open source, anyone can set out creating their own variation of Linux, using the Linux kernel and the GNU OS tools and programs.
There is no shortage of Linux distribution. Some are known for their ease of use, while others provide only the basic tools and require the user to configure and setup the system. The type you choose depends largely on the amount of customization you want, the amount of time you want to spend on it, and personal preference.
Types of Distributions
Some Linux distributions are specifically geared toward servers, and many of those come with commercial support. Among them are Red Hat Enterprise Linux, SUSE Linux Enterprise Server, and Oracle Enterprise Linux. There are also free distributions commonly used on servers, such as CentOS, Debian, and Gentoo.
What to Consider
Since you are looking to take your server online, you should ideally look for a distribution that will come with the necessary applications installed or make them easily installable. If you find it difficult to install and setup programs like OpenSSH, Apache, and MySQL, your Linux distribution is probably not good for a server.
You should also consider how much time you want to invest in the basics of setting up the server. While Linux distributions that require minute tweaking and configuration of every component are good for learning and for people who are tech enthusiasts, they are simply not practical for some businesses.
RHEL (Red Hat Enterprise Linux)
Red Hat is a trusted name among Linux users and is one of the oldest commercial Linux vendors. There are probably still servers out there running old versions of Red Hat Linux because of its reliability and longevity. RHEL is Red Hat's venture into commercial enterprise-level servers and is designed to run well on high-end servers and clusters. Red Hat provides commercial support, and the system as a whole can be pretty expensive for small businesses.
Red Hat uses the RPM packaging tool to install software and relies on YUM to distribute it, making online updates easy and usually painless. Red Hat tests programs vigorously before it marks them as ready to be included in future versions. Therefore, software versions of the latest RHEL are usually older than other Linux distributions.
If you like RHEL but do not have the money to pay for it, CentOS is an ideal choice. It is free of charge, yet maintains 100% binary compatibility with the upstream RHEL distribution. CentOS technical support is provided through the community mailing lists, web forums, and chat rooms. If you intend to use it, you will need to have someone on staff who is comfortable configuring Linux.
Another seasoned household name in the Linux world is Debian. It is a distribution that maintains a strong commitment to the free and open source movement, relying on community discussion and contributions to develop and manage the operating system. This makes the development process slow but very reliable and high quality.
Debian is well known for its easy-to-use package management system. It uses DEB packages and relies on a system called APT for installation, updates, and even in-box upgrades.
Like CentOS, using Debian will require some technical expertise, as support is purely community-based. There are many Debian-based distributions, but most are not designed for servers. Ubuntu, however, does offer a Server Edition and provides commercial support.
A distribution that is certainly not for the uninitiated, Slackware provides a high degree of stability and simplicity. It relies largely on upstream configurations and changes very little in the original software packages. One could call it a more pure version of Linux than many of the other distributions.
Like other non-commercial distributions, Slackware requires the system administrator to be knowledgeable about Linux configuration. Support is likewise provided by the community.
Slackware's package management system is called pkgtool and is very basic, but performs the necessary tasks for online distribution of packages.
Gentoo is a very different kind of Linux distribution. Some server administrators will swear by it, while others run from it. It borrows its design and package management from FreeBSD, which downloads source packages and compiles them according to the user's configuration settings. While it does simplify the source compiling process, it still takes longer than installing binary packages.
Gentoo allows the administrator to customize each and every aspect of the operating system. The result is a highly optimized server OS, built specifically for the hardware running it. This makes for a fast, clean server. Unfortunately, the process of getting there can be laborious and beyond the scope of many new server users.