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LINUX LICENSING

In most cases, when you obtain or “buy” software, you really do not own it. Rather, you are granted a license to use the software. The terms of the licensing agreement differ depending on the type of license accompanying the software. To understand software licensing, you should understand the following terms.

Open Source

- Software that is distributed with the source files. End users can modify and recompile the software to meet their needs. Usually developed as a community project. More specifically, Open Source is a certification mark for software that adheres to the Open Source Initiative standards.

Closed Source

- Software that is distributed without the source files.
Much commercially available software is closed source (such as Microsoft Windows, Word, and Excel).

Open Source

- Software distributed without cost. The software may be open source or closed source.

Free Software

- Software that is freely distributable, includes the source code, and allows the end user to modify or enhance the software.
Free software may be distributed at a cost. The “free” refers to the freedom of use, not necessarily no cost.
Linux is distributed as Open Source software (meeting OSI standards) under the GNU General

Public License (GPL). The GNU/GPL provides that:
• You are free to use the software and its source code as you want.
• You can redistribute the software, even charging a fee for the redistribution.
• The package must include the source code or an offer to make the source code available.
• The software has no guarantee. You can, however, offer your own guarantee, even charging for this service.
• If you modify the software, any modifications must remain unpatented, or, if patented, be made available for everyone’s use.
You should be aware that using Linux in your organization is not without cost. Although you do not pay for a license for Linux, expect to pay for the following items:
• Media containing the software components
• Technical support, automatic updates, and custom utilities
• Installation, maintenance, and system repair

PAGE TAGS: linux shells bash script commands, Linux Software Tutorial

LINUX SHELL

The shell is the interface between the user and the operating system. Via the shell, users and programs send commands to the kernel. Commands sent through a graphical interface or through applications interface directly with the shell without any noticeable events. In many ways, the shell is much like the DOS command interpreter. You can also open a terminal session or a command prompt window to type commands and receive responses back (similar to a DOS prompt in Windows).

Although most Linux distributions now include a graphical interface, and many administration tools have been converted to a graphical format, as an administrator you will find that some tasks are best performed from the command prompt. In addition, while graphical elements vary between distributions, shell commands are more likely to be consistent between distributions.

The shells you’re most likely to encounter come from two different derivations:

Bourne shells

- Bourne shells use syntax and conventions similar to a UNIX shell. sh is the original shell created by Steve Bourne. The bash shell (Bourne-again shell) includes many improvements and is the default shell for new Linux installations.

C-shells

- C-shells use syntax similar to the C programming language. The original C-shell (csh) has given way to more powerful derivations like tcsh, zsh, and ksh.
Like everything else in Linux, the shell is just a component. This means that you can choose the shell you want to use, or have multiple shells installed on your system at the same time. A list of shells on your system is stored in the /etc/shells file. The default shell for a user is stored in the user account database.

Despite their differences, all shells share some common characteristics:
• All shells are interfaces with the kernel, separate and distinct from it.
• Users can customize every shell using the shell’s commands.
• Shells are run both interactively by end users and noninteractively by the system.
• Shells can be run within one another either interactively when a user starts a second shell at the first shell’s command line, or noninteractively by the system when running scripts or programs.
• Shells use configuration files to establish their operating environments.
• All shells pass environment variables to child processes.
In this course, you will learn to use the bash shell and command prompt to execute commands and perform system maintenance tasks. Keep in mind the following tips for working in the shell.
• When entering commands, remember the format: command + switches + options. Unlike MS-DOS commands, switches come immediately following the command, not at the end.
• Use the clear command to clear the screen.
• If you hit the tab key while typing, bash searches for letters that complete what you’ve typed. If you’ve typed enough unique letters, bash completes the string for you.
• To access commands you’ve already entered into the system, use the arrow up or arrow down key. Find the command and hit enter to re-execute it. Alternatively, you can modify the command with new options, paths, or variables to make it a new command.

Page Tags: linux partition, linux volumes, installing linux partition, linux format, linux format partition, linux partitions, linux volume, Linux Software Tutorial

LINUX PARTITIONS AND VOLUMES

Prior to installing Linux, you should carefully plan you partition strategy. If you are not careful, you might finish off the installation with a single partition that holds all system and user files. A more efficient strategy is to create multiple partitions based on the types of files held on the partition and the user access needs to the data. In addition to planning which partitions you need and which files they will contain, you should also consider the mount options for each volume.

Following are some guidelines to follow to create an efficient partition scheme:

• For multi-boot systems, create a boot partition. Normally, this will hold the files necessary to boot the system. When using LILO, you must put this partition in the first 1024 blocks on the disk. It is recommended that the boot partition be a primary partition.
• Keep the root partition as small as possible. Include only those directories that are needed during boot. Necessary directories include:
o / (the root directory)
o /bin
o /boot (if not included as its own partition)
o /dev
o /etc
o /initrd
o /lib
o /proc
o /root
o /sbin
o /sys
• The partition holding the root directory should be on a primary partition and must be formatted with a Linux filesystem.
• Linux can use either a swap file or a swap partition for the swap area. Whenever possible, create a separate swap partition. The recommended size of the swap partition is twice the amount of RAM, up to a maximum of 2 GB on PC computers. To improve performance, you can even put multiple swap areas on multiple disks.
• Consider creating separate partitions for the following directories. Set mount options based on the type of files in the directory.
o /tmp mount noexec,nosuid
o /var mount noexec,nosuid
o /usr mount ro
o /home mount nosuid
• Create additional partitions for other operating systems. If your computer already has an operating system (such as Windows) that takes up most of the available drive space, use the FIPS utility to split the existing partition and make room for new partitions (FIPS only resizes existing partitions by splitting them). Use a third party utility to resize partitions. Do not use fdisk, as this will destroy existing data.
• Select the appropriate filesystem for each partition to support the operating system or provide necessary features.