What is Linux?
Linux represents the base of the LAMP Stack. Acting as the first layer of the model, Linux is what the “L” (of LAMP) stands for. Its name was inspired from the name of the Finnish scientist Linus Trovalds, who wrote the first Linux Kernel. Linux is built to be a free, open source, UNIX-like operating system. Over years, many flavors of Linux (called distributions) have been developed. The long list (may be hundreds) of Linux distributions contain brilliant names like: openSUSE, Debian, Mandriva, Gentoo, Ubuntu, and the star of this series: Red Hat. In 2008, Google created devised its own variation of Linux Kernel, Android, designed for targeting mobile phones and tablets.
- Linux is completely free.
- Being an open-source software encourages thousands of developers to download the Linux source code and work on it. When they come up with new ideas and share them with other developers, the whole developing community benefits from these contributions. That is why new Linux distributions appear everyday (even as we speak).
- Together; Linux, Apache, MySQL (now MariaDB), and Perl/PHP/Python constitute the components of the LAMP open-source solution stack.
Red Hat Enterprise Linux (RHEL)
Red Hat Enterprise Linux (RHEL) is an RPM-based Linux distribution, powered by Red Hat. Red Hat released its first Linux distribution in 1993.
Red Hat also sponsors the Fedora Project. Fedora versions contain the new features that Red Hat wants to give a try before being included in official RHEL versions.
Our focus in this course will be the administration of Red Hat Enterprise Linux 6.
Kernel versus Shell
We are only at the doors of the Linux world; nevertheless, you’ve already heard me saying something about a “Kernel”. In Linux, two common terms are used:
Kernel: this is the core of the Linux operating system. It is the layer directly on top of the hardware. It has the necessary modules required to deal with the underlying hardware devices.
Shell: the Linux shell is an interactive command-line interface where a user can type a command, and get its result(s). The Linux shell lies of top of the kernel.
Everything in Linux is a File
Yes, everything… everything in Linux is a file. That is a common rule that you should be aware of. User’s data, shell scripts, system commands, and the Linux kernel itself all are files.
User’s data are normal text files. System commands are executable binary files. And I guess that Shell scripts are files containing a group of commands to execute as a program.
Yes, all what you said is totally true. But, you may be astonished when you know that even hardware devices are treated as files: the disk drives, the CD-ROM, the physical volumes, the volume groups, the logical volumes, and the file systems as well.
If you come from a Windows background, the concept of LVM (Logical Volume Manager) will be new for you. LVM gives us the capability to combine several disks (physical volumes) into a larger entity. The new resulting entity is called volume group. The volume group now acts as if it were a disk to partition according to the storage requirements. It can be partitioned into one or more (may be hundreds) of logical volumes, on top of which file systems are created and mounted.
If you don’t understand, don’t worry. We will tackle all these concepts later in detail.
There are no prerequisites you need to have before you start reading these series of articles. All you need to know is just the basic knowledge of computers and operating systems, and how to use a computer. If you come from a Windows administration experience, you are encouraged to join us. If you have some knowledge in UNIX or Linux, that will help. But, if you don’t, don’t worry. We will understand it together, bit by bit, until you reach the level of knowledge you need.
Now, I know that you are very excited to start our journey with the Red Hat Administration. That will be soon. In the next article, we will start by learning how to install RHEL 6. Then, we will dive slowly into the course details. I say slowly because I want to give each topic the time and care it needs. This will ensure we build first a strong base to add upon later.