Red Hat Linux file system

Red Hat Linux file system :–

File system of any operating system used to be the structure, in which all the information on our system is stored. The file system is organized in hierarchy of directories, which may contain files or the sub-directories as well. These file system types determine how the information can be stored as files or as directory. In Linux there are following types file system, which we generally use: ext3, swap, LVM and RAID.

Linux file system structure –

Red Hat Linux organizes file into directories. The standard directories are as follows…

/ - This is top level root directory. The remaining directories are kept below this root (/) directory, i.e. these are sub-directories of root directory.

Note: / is different from root. Both are pronounced as root, but former is directory while later is a user with administrative privileges.

/root: The administrative user's home directory. Mind the difference between /, the root directory and /root, the home directory of the root user.

/home: This directory is place for keeping all the user’s home directories except root user.

/dev: This directory will list all available device drivers. Contains references to all the CPU peripheral hardware, which are represented as files with special properties.

/mnt: It contains the mount points of removable media, like /mnt/cdrecorder

/etc: It contains the basic Linux configuration files related to passwords, X window and daemons etc.

/boot: It stores the file and commands to boot Linux on our system.

/bin: It has all the basic command line utilities.

/lib: It lists program libraries, which may be needed by different applications or Linux kernel.

/proc: It includes the kernel related processes which are running currently.

/initrd: It configures one empty directory which is used by Initial RAM disk during boot. We should not delete this directory; else we will not be able to boot the Linux system.

/sbin: It contains commands for system administration.

/var: It contains log file and print spools etc. Storage for all variable files and temporary files created by users, such as log files, the mail queue, the print spooler area, space for temporary storage of files downloaded from the Internet, or to keep an image of a CD before burning it.

/usr: It contains programs and data which is available to all the users. Programs, libraries, documentation etc. for all user-related programs.

/temp: Temporary space for use by the system, cleaned upon reboot, so don't use this for saving any work!

/lost+found: Every partition has a lost+found in its upper directory. Files that were saved during failures are here.

Basic hardware requirements

Basic hardware requirements –

                   If you want to install Enterprise Linux, install additional software, configure a graphical user interface (GUI) or setup a server then the minimum requirements will be as follows –

CPU                                     :    Pentium – class

For text mode install    :    200 MHz Pentium class or better

For graphical mode     :   400 MHz Pentium class II or better

RAM 64 MB                  :    for workstations in text mode

128MB                  :   for Graphical Workstations

Hard Disk 600 MB for custom minimum and 256 MB for swap. It can go up for other types of installations, like 6.9 GB for custom everything and 256 MB for swap

Current application of Linux systems

Current application of Linux systems –

                      Today Linux has joined the desktop market. Linux developers concentrated on networking and services in the beginning and office applications have been the last barrier to be taken down. We don't like to admit that Microsoft is ruling this market, so plenty of alternatives have been started over the last couple of years to make Linux an acceptable choice as a workstation, providing an easy user interface and MS compatible office applications like word processors, spreadsheets, presentations and the like. On the server side, Linux is well-known as a stable and reliable platform, providing database and trading services for companies like Amazon, the well-known online bookshop, US Post Office, the German army and many others. Especially Internet providers and Internet service providers have grown fond of Linux as firewall, proxy- and web server, and you will find a Linux box within reach of every UNIX system administrator who appreciates a comfortable management station. Clusters of Linux machines are used in the creation of movies such as "Titanic", "Shrek" and others. In post offices, they are the nerve centers that route mail and in large search engine, clusters are used to perform internet searches. These are only a few of the thousands of heavy-duty jobs that Linux is performing day-to-day across the world. It is also worth to note that modern Linux not only runs on workstations, mid- and high-end servers, but also on "gadgets" like PDA's, mobiles, a shipload of embedded applications and even on experimental wristwatches. This makes Linux the only operating system in the world covering such a wide range of hardware.

Properties of Linux

Properties of Linux –

                   A lot of the advantages of Linux are a consequence of Linux' origins, deeply rooted in UNIX, except for the first advantage, of course:-

1- Linux is free –

               As in free beer, they say. If you want to spend absolutely nothing, you don't even have to pay the price of a CD. Linux can be downloaded in its entirety from the Internet completely for free. No registration fees, no costs per user, free updates, and freely available source code in case you want to change the behavior of your system. Most of all, Linux is free as in free speech: The license commonly used is the GNU Public License (GPL). The license says that anybody who may want to do so has the right to change Linux and eventually to redistribute a changed version, on the one condition that the code is still available after redistribution. In practice, you are free to grab a kernel image, for instance to add support for teletransportation machines or time travel and sell your new code, as long as your customers can still have a copy of that code.

2- Linux is portable to any hardware platform –

               A vendor who wants to sell a new type of computer and who doesn't know what kind of OS his new machine will run (say the CPU in your car or washing machine), can take a Linux kernel and make it work on his hardware, because documentation related to this activity is freely available.

3- Linux was made to keep on running –

             As with UNIX, a Linux system expects to run without rebooting all the time. That is why a lot of tasks are being executed at night or scheduled automatically for other calm moments, resulting in higher availability during busier periods and a more balanced use of the hardware. This property allows for Linux to be applicable also in environments where people don't have the time or the possibility to control their systems night and day.

4- Linux is secure and versatile –

                The security model used in Linux is based on the UNIX idea of security, which is known to be robust and of proven quality. But Linux is not only fit for use as a fort against enemy attacks from the Internet: it will adapt equally to other situations, utilizing the same high standards for security. Your development machine or control station will be as secure as your firewall.

5- Linux is scalable –

              From a Palmtop with 2 MB of memory to a pet byte storage cluster with hundreds of nodes: add or remove the appropriate packages and Linux fits all. You don't need a supercomputer anymore, because you can use Linux to do big things using the building blocks provided with the system. If you want to do little things, such as making an operating system for an embedded processor or just recycling your old 486, Linux will do that as well.

6- The Linux OS and most Linux applications have very short debug-times –

                Because Linux has been developed and tested by thousands of people, both errors and people to fix them are usually found rather quickly. It sometimes happens that there are only a couple of hours between discovery and fixing of a bug.

Redhat Linux features

Does Linux have a future? –

                       No matter what version of Linux you use, the piece of code common to all is the Linux kernel. Although the kernel can be modified to include support for the features you want, every Linux kernel can offer the following features –

A- Open Source –

                 The idea behind Open Source software is rather simple: when programmers can read, distribute and change Code, the code will mature. People can adapt it, fix it, debug it, and they can do it at a speed that dwarfs the performance of software developers at conventional companies. This software will be more flexible and of a better quality than software that has been developed using the conventional channels, because more people have tested it in more different conditions than the closed software developer ever can. The Open Source initiative started to make this clear to the commercial world, and very slowly, commercial vendors are starting to see the point. While lots of academics and technical people have already been convinced for 20 years now that this is the way to go, commercial vendors needed applications like the Internet to make them realize they can profit from Open Source. Now Linux has grown past the stage where it was almost exclusively an academic system, useful only to a handful of people with a technical background. Now Linux provides more than the operating system: there is an entire infrastructure supporting the chain of effort of creating an operating system, of making and testing programs for it, of bringing everything to the users, of supplying  maintenance, updates and support and customizations, etcetera. Today, Linux is ready to accept the challenge of a fast-changing world.

B- Ten years of experience at your service –

                                                     While Linux is probably the most well-known Open Source initiative, there is another project that contributed enormously to the popularity of the Linux operating system. This project is called SAMBA, and its achievement is the reverse engineering of the Server Message Block (SMB)/Common Internet File System (CIFS) protocol used for file- and print-serving on PC-related machines, natively supported by MS Windows NT and OS/2, and Linux. Packages are now available for almost every system and provide interconnection solutions in mixed environments using MS Windows protocols: Windows-compatible (up to and includingWinXP) file- and print-servers. Maybe even more successful than the SAMBA project is the Apache HTTP server project. The server runs on UNIX, Windows NT and many other operating systems. Originally known as "Apache Server", based on existing code and a series of "patch files", the name for the matured code deserves to be connoted with the Native American tribe of the Apache, well-known for their superior skills in warfare strategy and inexhaustible endurance. Apache has been shown to be substantially faster, more stable and more feature-full than many other web servers. Apache is run on sites that get millions of visitors per day, and while no official support is provided by the developers, the Apache user community provides answers to all your questions. Commercial support is now being provided by a number of third parties. In the category of office applications, a choice of MS Office suite clones is available, ranging from partial to full implementations of the applications available on MS Windows workstations. These initiatives helped a great deal to make Linux acceptable for the desktop market, because the users don't need extra training to learn how to work with new systems. With the desktop come the praise of the common users, and not only their praise, but also their specific requirements, which are growing more intricate and demanding by the day. The Open Source community, consisting largely of people who have been contributing for over half a decade, assures Linux' position as an important player on the desktop market as well as in General IT application. Paid employees and volunteers alike are working diligently so that Linux can maintain a position in the market. The more users, the more questions. The Open Source community makes sure answers keep coming, and watches the quality of the answers with a suspicious eye, resulting in ever more stability and accessibility. Listing all the available Linux software is beyond the scope of this guide, as there are tens of thousands of packages. Throughout this course we will present you with the most common packages, which are almost all freely available. In order to take away some of the fear of the beginning user, here's a screenshot of one of your most-wanted programs. You can see for yourself that no effort has been spared to make users who are switching from Windows feel at home.

C- Multi-user –

             Not only can you have many user accounts available on a Linux system, you can also have multiple users logged in and working on the system at the same time. Users can have their own environments arranged the way they want: their own home directory for storing files and their own desktop interface (with icons, menus and applications arranged to suit them). User accounts can be password-protected, so that users can control who has access to their applications and data.

D- Multitasking –

                  In Linux, it is possible to have many programs running at the same time, which means that not only can you have many programs going at once, but that the Linux operating system can it self have programs running in the background. Many of these system processes make it possible for Linux to work as a server, with these background processes listening of the network for requests to log in to your system, view a web page, print a document, or copy a file. These background processes are referred to as daemons.

E- Hardware support –

                   You can configure support for almost every type of hardware that can be connected to a computer. There is support for floppy disk drive, CD-ROMs, removable disk (such as DVDs and USB flash drives), sound cards, tape devices, video cards and most anything else you can think of. As device interface, such as USB and FireWire, have been added to computers, support for those devices has been added to Linux as well.

For Linux to support a hardware device, Linux needs a driver, a piece of software that interfaces between the Linux kernel and the devices. Drivers are available in the Linux kernel to support hundreds of computer hardware components that can be added or removed as needed.

F- Networking connectivity –

                       To connect your Linux system to a network, Linux offers support for a variety of local area network (LAN) card, modems, and serial devices. In addition to LAN protocols, such as Ethernet (both wired and wireless), all the most popular upper-level networking protocols can be built-in. the most popular of these protocols is TCP/IP (used to connect to the internet). Other protocols, such as IPX (for Novell network) and X.25 (a packet-switching network type that is popular in Europe), are also available.

G- Network servers –

                       Providing networking services to the client computers on the LAN or to the entire Internet is what Linux does best. A variety of software packages are available that enable you to use Linux as a print server, file server, FTP server, mail server, web server, news server, or work-group (DHCP or NIS) server.

To make a Linux distribution useful, components need to be added on top of the Linux kernel. For humans to access a Linux system, they can enter commands to a shell or use graphical interface to open menus, windows, and icons. Then you need actual applications to run. In particular, a useful Linux desktop system includes the following:-

H- Graphical user Interface (X Windows system) –

                       The powerful framework for working with graphical application in Linux is referred to as the X window System (or simply X). X handles the functions of opening X-based graphical user interface (GUI) applications and displaying them on an X server process (the process that manages your screen, mouse, and keyboard). Fedora and RHEL focus on the GNOME and KDE desktop environments, but also have several other desktop environments and window managers available.

I- Application support –

                        Because of compatibility with POSIX and several different application programming interface (APIs), a wide range of free and open source software is available for Linux system. Compatibility with the GNU C libraries is a major reason for the wide-ranging application support. Often, making as open source application available to a particular version of Linux can be done by simply recompiling the source code to run on that Linux version.

J- Advance Security –

                     SSL is the advance security in linux operating system.

The user interface

Is Linux difficult? –

            Whether Linux is difficult to learn depends on the person you're asking. Experienced UNIX users will say no, because Linux is an ideal operating system for power-users and programmers, because it has been and is being developed by such people. Everything a good programmer can wish for is available: compilers, libraries, development and debugging tools. These packages come with every standard Linux distribution. The C-compiler is included for free – as opposed to many UNIX distributions demanding licensing fees for this tool. All the documentation and manuals are there, and examples are often included to help you get started in no time. It feels like UNIX and switching between UNIX and Linux is a natural thing. In the early days of Linux, being an expert was kind of required to start using the system. Those who mastered Linux felt better than the rest of the "users" who hadn't seen the light yet. While the manuals were on every system, it was difficult to find the documentation, and even if someone did, explanations were in such technical terms that the new user became easily discouraged from learning the system. The Linux-using community started to realize that if Linux was ever to be an important player on the operating system market, there had to be some serious changes in the accessibility of the system.

History of Linux

History of Linux –

                In order to understand the popularity of Linux, we need to travel back in time, about 30 years ago...

UNIX –

            Imagine computers as big as houses, even stadiums. While the sizes of those computers posed substantial problems, there was one thing that made this even worse: every computer had a different operating system. Software was always customized to serve a specific purpose, and software for one given system didn't run on another system. Being able to work with one system didn't automatically mean that you could work with another. It was difficult, both for the users and the system administrators. Computers were extremely expensive then, and sacrifices had to be made even after the original purchase just to get the users to understand how they worked. The total cost per unit of computing power was enormous.

Technologically the world was not quite that advanced, so they had to live with the size for another decade. In 1969, a team of developers in the Bell Labs laboratories started working on a solution for the software problem, to address these compatibility issues. They developed a new operating system, which was

1.  Simple and elegant.

2. Written in the C programming language instead of in assembly code.

3.  Able to recycle code.

The Bell Labs developers named their project "UNIX."

The code recycling features were very important. Until then, all commercially available computer systems were written in a code specifically developed for one system. UNIX on the other hand needed only a small piece of that special code, which is now commonly named the kernel. This kernel is the only piece of code that needs to be adapted for every specific system and forms the base of the UNIX system. The operating system and all other functions were built around this kernel and written in a higher programming language, C. This language was especially developed for creating the UNIX system. Using this new technique, it was much easier to develop an operating system that could run on many different types of hardware. The software vendors were quick to adapt, since they could sell ten times more software almost effortlessly. Weird new situations came in existence: imagine for instance computers from different vendors communicating in the same network, or users working on different systems without the need for extra education to use another computer. UNIX did a great deal to help users become compatible with different systems. Throughout the next couple of decades the development of UNIX continued. More things became possible to do and more hardware and software vendors added support for UNIX to their products. UNIX was initially found only in very large environments with mainframes and minicomputers (note that a PC is a "micro" computer). You had to work at a university, for the government or for large financial corporations in order to get your hands on a UNIX system. But smaller computers were being developed, and by the end of the 80's, many people had home computers. By that time, there were several versions of UNIX available for the PC architecture, but none of them were truly free and more important: they were all terribly slow, so most people ran MS DOS or Windows 3.1 on their home PCs.

What is linux

What is Linux?-

Linux is a free operating system that was created by Linus Torvalds when he was a student at the University of Helsinki in 1991. Torvalds started Linux by writing a kernel (the heart of the operating system) partly from scratch and partly by using publicly available software. Torvalds then released the system to his friends and to a community of “hackers” on the internet and asked them to work with it, fix it, and enhanced it. It took off. Today, there are thousands of software developers around the world contributing software to the open source community that feeds the Linux initiative. Because the source code for the software is freely available, any one can work on it, change it, or enhanced it. Developers are encouraged to pass their fixes and improvements back in to the community so that the Linux can continue to grow and improve...