Redhat Enterprise linux

Touch Command

abrazaq@gmail.com — Sat, 01 Oct 2011 10:37:00 +0000

NAME

touch - change file timestamps

SYNOPSIS

touch [OPTION]... FILE...

DESCRIPTION

Update the access and modification times of each FILE to the current time. A FILE argument that does not exist is created empty, unless -c or -h is supplied.

A FILE argument string of - is handled specially and causes touch to change the times of the file associated with standard output.

Mandatory arguments to long options are mandatory for short options too.

-a change only the access time

-c, --no-create do not create any files

-d, --date=STRING parse STRING and use it instead of current time

-h, --no-dereference affect each symbolic link instead of any referenced file (useful only on systems that can change the timestamps of a symlink)

-m change only the modification time

-r, --reference=FILE use this file’s times instead of current time

-t STAMP use [[CC]YY]MMDDhhmm[.ss] instead of current time

--time=WORD change the specified time: WORD is access, atime, or use: equivalent to -a WORD is modify or mtime: equivalent to –m

--help display this help and exit

--version output version information and exit

Note that the -d and -t options accept different time-date formats.

DATE STRING

The --date=STRING is a mostly free format human readable date string such as "Sun, 29 Feb 2004 16:21:42 -0800" or "2004-02-29 16:21:42" or even "next Thursday". A date string may contain items indicating calendar date, time of day, time zone, day of week, relative time, relative date, and numbers. An empty string indicates the beginning of the day. The date string format is more complex than is easily documented here but is fully described in the info documentation.

mkdir Command

abrazaq@gmail.com — Fri, 30 Sep 2011 11:16:00 +0000

NAME

mkdir - make directories

SYNOPSIS

mkdir [OPTION]... DIRECTORY...

DESCRIPTION

Create the DIRECTORY(ies), if they do not already exist. Mandatory arguments to long options are mandatory for short options too.

-m, --mode=MODE set file mode (as in chmod), not a=rwx - umask

-p, --parents no error if existing, make parent directories as needed

-v, --verbose print a message for each created directory

-Z, --context=CTX set the SELinux security context of each created directory to CTX

--help display this help and exit

--version output version information and exit

rm Command

abrazaq@gmail.com — Fri, 30 Sep 2011 11:15:00 +0000

NAME

rm - remove files or directories

SYNOPSIS

rm [OPTION]... FILE...

DESCRIPTION

This manual page documents the GNU version of rm. rm removes each specified file. By default, it does not remove directories.

If the -I or --interactive=once option is given, and there are more than three files or the -r, -R, or - -recursive are given, then rm prompts the user for whether to proceed with the entire operation. If the response is not affirmative, the entire command is aborted. Otherwise, if a file is unwritable, standard input is a terminal, and the -f or --force option is not given, or the -i or --interactive=always option is given, rm prompts the user for whether to remove the file. If the response is not affirmative, the file is skipped.

OPTIONS

Remove (unlink) the FILE(s).

-f, --force ignore nonexistent files, never prompt

-i prompt before every removal

-I prompt once before removing more than three files, or when removing recursively. Less intrusive than -i, while still giving protection against most mistakes

--interactive[=WHEN] prompt according to WHEN: never, once (-I), or always (-i). Without WHEN, prompt always one-file-system. when removing a hierarchy recursively, skip any directory that is on a file system different from that of the corresponding command line argument

--no-preserve-root do not treat ‘/’ specially

--preserve-root do not remove ‘/’ (default)

-r, -R, --recursive remove directories and their contents recursively

-v, --verbose explain what is being done

--help display this help and exit

--version output version information and exit

By default, rm does not remove directories. Use the --recursive (-r or -R) option to remove each listed directory, too, along with all of its contents. To remove a file whose name starts with a ‘-’, for example ‘-foo’, use one of these commands:

rm -- -foo

rm ./-foo

Note that if you use rm to remove a file, it is usually possible to recover the contents of that file. If you want more assurance that the contents are truly unrecoverable, consider using shred.

mv Command

abrazaq@gmail.com — Fri, 30 Sep 2011 11:14:00 +0000

NAME

mv - move (rename) files

SYNOPSIS

mv [OPTION]... [-T] SOURCE DEST

mv [OPTION]... SOURCE... DIRECTORY

mv [OPTION]... -t DIRECTORY SOURCE...

DESCRIPTION

Rename SOURCE to DEST, or move SOURCE(s) to DIRECTORY. Mandatory arguments to long options are mandatory for short options too.

--backup [=CONTROL] make a backup of each existing destination file

-b like --backup but does not accept an argument

-f, --force do not prompt before overwriting

-i, --interactive prompt before overwrite

-n, --no-clobber do not overwrite an existing file

If you specify more than one of -i, -f, -n, only the final one takes effect.

--strip-trailing-slashes remove any trailing slashes from each SOURCE argument

-S, --suffix=SUFFIX override the usual backup suffix

-t, --target-directory=DIRECTORY move all SOURCE arguments into DIRECTORY

-T, --no-target-directory treats DEST as a normal file

-u, --update move only when the SOURCE file is newer than the destination file or when the destination file is missing

-v, --verbose explain what is being done

--help display this help and exit

--version output version information and exit

The backup suffix is ‘~’, unless set with --suffix or SIMPLE_BACKUP_SUFFIX. The version control method may be selected via the --backup option or through the VERSION_CONTROL environment variable.

Here are the values:

none, off never make backups (even if --backup is given)

numbered, t make numbered backups existing, nil

Numbered if numbered backups exist, simple otherwise simple, never always make simple backups

CP Command

abrazaq@gmail.com — Fri, 30 Sep 2011 11:13:00 +0000

NAME

cp - copy files and directories

SYNOPSIS

cp [OPTION]... [-T] SOURCE DEST

cp [OPTION]... SOURCE... DIRECTORY

cp [OPTION]... -t DIRECTORY SOURCE...

DESCRIPTION

Copy SOURCE to DEST, or multiple SOURCE(s) to DIRECTORY. Mandatory arguments to long options are mandatory for short options too.

-a, --archive same as -dR --preserve=all

--backup[=CONTROL] make a backup of each existing destination file

-b like --backup but does not accept an argument

--copy-contents copy contents of special files when recursive

-d same as --no-dereference --preserve=links

-f, --force if an existing destination file cannot be opened, remove it and try again (redundant if the -n option is used)

-i, --interactive prompt before overwrite (overrides a previous -n option)

-H follow command-line symbolic links in SOURCE

-l, --link link files instead of copying

-L, --dereference always follow symbolic links in SOURCE

-n, --no-clobber do not overwrite an existing file (overrides a previous –I option)

-P, --no-dereference never follow symbolic links in SOURCE

-p same as --preserve = mode,ownership,timestamps

--preserve[=ATTR_LIST] preserve the specified attributes (default: mode, ownership, timestamps), if possible additional attributes: context , links, xattr, all

-c same as --preserve=context

--no-preserve=ATTR_LIST don’t preserve the specified attributes

--parents use full source file name under DIRECTORY

-R, -r, --recursive copy directories recursively

--reflink[=WHEN] control clone/CoW copies. See below.

--remove-destination remove each existing destination file before attempting to open it (contrast with --force)

--sparse=WHEN control creation of sparse files. See below.

--strip-trailing-slashes remove any trailing slashes from each SOURCE argument

-s, --symbolic-link make symbolic links instead of copying

-S, --suffix=SUFFIX override the usual backup suffix

-t, --target-directory=DIRECTORY copy all SOURCE arguments into DIRECTORY -T, --no-target-directory treat DEST as a normal file

-u, --update copy only when the SOURCE file is newer than the destination file or when the destination file is missing

-v, --verbose explain what is being done

-x, --one-file-system stay on this file system

-Z, --context=CONTEXT set security context of copy to CONTEXT --help display this help and exit

--version output version information and exit By default, sparse SOURCE files are detected by a crude heuristic and the corresponding DEST file is made sparse as well. That is the behavior selected by --sparse=auto. Specify --sparse=always to create a sparse DEST file whenever the SOURCE file contains a long enough sequence of zero bytes. Use --sparse=never to inhibit creation of sparse files.

When --reflink[=always] is specified, perform a lightweight copy, where the data blocks are copied only when modified. If this is not possible the copy fails, or if --reflink=auto is specified, fall back to a standard copy.

The backup suffix is ‘~’, unless set with --suffix or SIMPLE_BACKUP_SUFFIX. The version control method may be selected via the --backup option or through the VERSION_CONTROL environment variable.

Here are the values:

none, off never make backups (even if --backup is given) numbered, make numbered backups existing, nil numbered if numbered backups exist, simple otherwise simple, never always make simple backups. As a special case, cp makes a backup of SOURCE when the force and backup options are given and SOURCE and DEST are the same name for an existing, regular file.

Which Command

abrazaq@gmail.com — Fri, 30 Sep 2011 11:12:00 +0000

NAME

which - shows the full path of (shell) commands.

SYNOPSIS

which [options] [--] programname [...]

DESCRIPTION

Which takes one or more arguments. For each of its arguments it prints to stdout the full path of the executables that would have been executed when this argument had been entered at the shell prompt. It does this by searching for an executable or script in the directories listed in the environment variable PATH using the same algorithm as bash(1).

This man page is generated from the file which.texinfo.

OPTIONS

--all, -a Print all matching executables in PATH, not just the first.

--read-alias, -I Read aliases from stdin, reporting matching ones on stdout. This is useful in combination with using an alias for which it self. For example

alias which=´alias | which -i´.

--skip-alias Ignore option `--read-alias´, if any. This is useful to explicity search for normal binaries, while using the `--read-alias´ option in an alias or function for which.

--read-functions Read shell function definitions from stdin, reporting matching ones on stdout. This is useful in combination with using a shell function for which itself. For example:

which() { declare -f | which --read-functions $@ }

export -f which

--skip-functions Ignore option `--read-functions´, if any. This is useful to explicity search for normal binaries, while using the `--read-functions´ option in an alias or function for which.

--skip-dot Skip directories in PATH that start with a dot.

--skip-tilde Skip directories in PATH that start with a tilde and executables which reside in the HOME directory.

--show-dot If a directory in PATH starts with a dot and a matching executable was found for that path, then print "./programname" rather than the full path.

--show-tilde Output a tilde when a directory matches the HOME directory. This option is ignored when which is invoked as root.

--tty-only Stop processing options on the right if not on tty.

--version,-v,-V Print version information on standard output then exit successfully.

--help Print usage information on standard output then exit successfully.

EXAMPLE

The recommended way to use this utility is by adding an alias (C shell) or shell function (Bourne shell) for which like the following:

[ba]sh:

which ()

{

(alias; declare -f) | /usr/bin/which --tty-only --read-alias --read-functions --show-tilde --show-dot $@

}

export -f which

[t]csh:

alias which ´alias | /usr/bin/which --tty-only --read-alias --show-dot --show-tilde´

This will print the readable ~/ and ./ when starting which from your prompt, while still printing the full path when used from a script:

> which q2

~/bin/q2

> echo `which q2`

/home/carlo/bin/q2

BUGS

The HOME directory is determined by looking for the HOME environment variable,which aborts when this variable doesn´t exist. Which will consider two equivalent directories to be different when one of them contains a path with a symbolic link.

who command

abrazaq@gmail.com — Fri, 30 Sep 2011 11:05:00 +0000

NAME

who - show who is logged on

SYNOPSIS

who [OPTION]... [ FILE | ARG1 ARG2 ]

DESCRIPTION

Print information about users who are currently logged in.

-a, --all same as -b -d --login -p -r -t -T -u

-b, --boot time of last system boot

-d, --dead print dead processes

-H, --heading print line of column headings

-l, --login print system login processes

--lookup attempt to canonicalize hostnames via DNS

-m only hostname and user associated with stdin

-p, --process print active processes spawned by init

-q, --count all login names and number of users logged on

-r, --runlevel print current runlevel

-s, --short print only name, line, and time (default)

-t, --time print last system clock change

-T, -w, --mesg add user’s message status as +, - or ?

-u, --users list users logged in

--message same as -T

--writable same as -T

--help display this help and exit

--version output version information and exit

If FILE is not specified, use /var/run/utmp. /var/log/wtmp as FILE is common. If ARG1 ARG2 given, -m presumed: ‘am i’ or ‘mom likes’ are usual.

Pwd Command

abrazaq@gmail.com — Sat, 24 Sep 2011 16:58:00 +0000

NAME
pwd - print name of current/working directory

SYNOPSIS pwd [OPTION]...

DESCRIPTION

Print the full filename of the current working directory.

-L, --logical use PWD from environment, even if it contains symlinks

-P, --physical avoid all symlinks

--help display this help and exit

--version output version information and exit

NOTE: your shell may have its own version of pwd, which usually supersedes the version described here. Please refer to your shell’s documentation for details about the options it supports.

Redhat Enterprise linux 6 Installation

abrazaq@gmail.com — Sat, 24 Sep 2011 10:41:00 +0000

RHEL-6 Installation Part 1

RHEL-6 Installation Part 2

RHEL-6 Installation Part3

IF you have any question, quarry, suggestion please comments or email to Admin. Thanks

The Power of ls Command

abrazaq@gmail.com — Sun, 18 Sep 2011 15:31:00 +0000

NAME

ls - List directory contents

SYNOPSIS

ls [OPTION]... [FILE]...

DESCRIPTION

List information about the FILEs (the current directory by default). Sort entries alphabetically if none of -cftuvSUX nor --sort.

Mandatory arguments to long options are mandatory for short options too.

-a, --all do not ignore entries starting with .

-A, --almost-all do not list implied . and ..

--author with -l, print the author of each file

-b, --escape print octal escapes for nongraphic characters

--block-size=SIZE use SIZE-byte blocks. See SIZE format below

-B, --ignore-backups do not list implied entries ending with ~

-c with -lt: sort by, and show, ctime (time of last modification of file status information) with -l: show ctime and sort by name otherwise: sort by ctime

-C list entries by columns

--color[=WHEN] colorize the output. WHEN defaults to ‘always’ or can be ‘never’ or ‘auto’. More info below

-d, --directory list directory entries instead of contents, and do not dereference symbolic links

-D, --dired generate output designed for Emacs’ dired mode

-f do not sort, enable -aU, disable -ls --color

-F, --classify append indicator (one of */=>@|) to entries

--file-type likewise, except do not append ‘*’

--format=WORD across -x, commas -m, horizontal -x, long -l, single-column -1, verbose -l, vertical -C

--full-time like -l --time-style=full-iso

-g like -l, but do not list owner

--group-directories-first group directories before files.

augment with a --sort option, but any use of --sort=none (-U) disables grouping

-G, --no-group in a long listing, don’t print group names

-h, --human-readable with -l, print sizes in human readable format (e.g., 1K 234M 2G)

--si likewise, but use powers of 1000 not 1024

-H, --dereference-command-line follow symbolic links listed on the command line

--dereference-command-line-symlink-to-dir follow each command line symbolic link that points to a directory

--hide=PATTERN do not list implied entries matching shell PATTERN (overridden by -a or -A)

--indicator-style=WORD append indicator with style WORD to entry names: none (default), slash (-p), file-type (--file-type), classify (-F)

-i, --inode print the index number of each file

-I, --ignore=PATTERN do not list implied entries matching shell PATTERN

-k like --block-size=1K

-l use a long listing format

-L, --dereference

when showing file information for a symbolic link, show information for the file the link references rather than for the link itself

-m fill width with a comma separated list of entries

-n, --numeric-uid-gid like -l, but list numeric user and group IDs

-N, --literal print raw entry names (don’t treat e.g. control characters specially)

-o like -l, but do not list group information

-p, --indicator-style=slash append / indicator to directories

-q, --hide-control-chars print ? instead of non graphic characters

--show-control-chars show non graphic characters as-is (default unless program is ‘ls’ and output is a terminal)

-Q, --quote-name enclose entry names in double quotes

--quoting-style=WORD use quoting style WORD for entry names: literal, locale, shell, shell-always, c, escape

-r, --reverse reverse order while sorting

-R, --recursive list subdirectories recursively

-s, --size print the allocated size of each file, in blocks

-S sort by file size --sort=WORD sort by WORD instead of name: none -U, extension -X, size -S, time -t, version -v

--time=WORD

with -l, show time as WORD instead of modification time: atime -u, access -u, use -u, ctime -c, or status -c; use specified time as sort key if --sort=time

--time-style=STYLE with -l, show times using style STYLE: full-iso, long-iso, iso, locale, +FORMAT. FORMAT is interpreted like ‘date’; if FORMAT

is FORMAT1<newline>FORMAT2, FORMAT1 applies to non-recent files and FORMAT2 to recent files; if STYLE is prefixed with

‘posix-’, STYLE takes effect only outside the POSIX locale

-t sort by modification time

-T, --tabsize=COLS assume tab stops at each COLS instead of 8

-u with -lt: sort by, and show, access time with -l: show access time and sort by name otherwise: sort by access time

-U do not sort; list entries in directory order

-v natural sort of (version) numbers within text

-w, --width=COLS assume screen width instead of current value

-x list entries by lines instead of by columns

-X sort alphabetically by entry extension

-1 list one file per line SELinux options:

--lcontext Display security context. Enable -l. Lines will probably be too wide for most displays.

-Z, --context Display security context so it fits on most displays. Displays only mode, user, group, security context and file name.

--scontext Display only security context and file name.

--help display this help and exit

--version output version information and exit

SIZE may be (or may be an integer optionally followed by) one of following: KB 1000, K 1024, MB 1000*1000, M 1024*1024, and so on for

G, T, P, E, Z, Y.

Using color to distinguish file types is disabled both by default and with --color=never. With --color=auto, ls emits color codes

only when standard output is connected to a terminal. The LS_COLORS environment variable can change the settings. Use the dircolors command to set it.

Exit status:

0 if OK,

1 if minor problems (e.g., cannot access subdirectory),

2 if serious trouble (e.g., cannot access command-line argument).

AUTHOR

Written by Richard M. Stallman and David MacKenzie.

Installing Red Hat Enterprise Linux 5 Step by Step

abrazaq@gmail.com — Sat, 17 Sep 2011 18:03:00 +0000

1. Power on your system. Press the appropriate key, typically ESC, F12, or DEL. If a boot menu isn’t available, you’ll need to adjust the boot sequence in the computer BIOS, which you can then use to boot directly from your selected media. Set your computer’s BIOS to boot from the first installation CD or USB drive. Details vary by PC. Make sure your BIOS saves your changes before you reboot.

2. You’ll see the first installation screen. Click Next.

3. You’ve already selected a language and keyboard, so the next step, if you’re actually running Red Hat Enterprise Linux 5 (as opposed to one of the rebuild distributions), is to enter an installation number associated with your purchased or trial subscription, as shown Here

4. Partition configuration based on your memory and available hard disk space (based on free space after removing partitions), or choose to customize the configuration

5. If there are existing partitions on the installed hard drives, you’ll get the chance to confirm that you want to remove said partitions (this step isn’t final). If you’re configuring a dual-boot with another operating system, don’t delete the partitions! Instead, click back and select Create A Custom Layout.

6. Now inspect and change partitions in Disk Druid, as shown. You can also create and then configure RAID and LVM partitions. And Then Click Next.

7. Once you’ve configured your partitions, set up a boot loader. If you select No Boot Loader Will Be Installed, you’ll need to use a third-party boot loader such as Partition Magic or Microsoft’s NTLDR. Unless you want to set up a Boot Loader Password or Configure Advanced Boot Loader Options, click Next.

8. Configure your connection to the network. If you don’t want the DHCP server to assign a hostname (or you don’t have a DHCP server), you can assign it manually, as shown here. Click Next to move on.

9. Set the time zone for your system. If you don’t have another operating system on this computer, keep the System Clock Uses UTC option active. Then click Next.

10. Type in and confirm the root password for your system. Click Next

11. There are two package customization screens available. Click Next

12. Select the package groups of your choice. This should conform to the requirements of the Installation and Configuration section of your particular packages. Click Next.

13. Once you’ve selected the package groups of your choice, you get one last chance to go back before starting the installation process. Click Next if you’re happy with your choices, or click Back to make changes.

14. The next screen congratulates you for completing the installation. The next step is to reboot your computer into RHEL. Click Reboot.

Hope the Above Redhat enterprise Linux 5 step by step installation. If you have any question or query ask at any time.

Redhat Enterprise Linux Text mode

abrazaq@gmail.com — Tue, 13 Sep 2011 10:21:00 +0000

You know you're in text mode when the whole screen is black, showing (in most cases white) characters. A text mode login screen typically shows some information about the machine you are working on, the name of the machine and a prompt waiting for you to log in:

RedHat Linux Enterprise Release 5.0 (Psyche)

blast login: _

The login is different from a graphical login, in that you have to hit the Enter key after providing your user name, because there are no buttons on the screen that you can click with the mouse. Then you should type your password, followed by another Enter. You won't see any indication that you are entering something, not even an asterisk, and you won't see the cursor move. But this is normal on Linux and is done for security reasons.

When the system has accepted you as a valid user, you may get some more information, called the message of the day, which can be anything. Additionally, it is popular on UNIX systems to display a fortune cookie, which contains some general wise or unwise (this is up to you) thoughts. After that, you will be given a shell, indicated with the same prompt that you would get in graphical mode.

Don't log in as root

Also in text mode: log in as root only to do setup and configuration that absolutely requires administrator privileges, such as adding users, installing software packages, and performing network and other system configuration. Once you are finished, immediately leave the special account and resume your work as a non-privileged user. Alternatively, some systems, like Ubuntu, force you to use sudo, so that you do not need direct access to the administrative account. Logging out is done by entering the logout command, followed by Enter. You are successfully disconnected from the system when you see the login screen again.

The power button

While Linux was not meant to be shut off without application of the proper procedures for halting the system, hitting the power button is equivalent to starting those procedures on newer systems. However, powering off an old system without going through the halting process might cause severe damage! If you want to be sure, always use the Shutdown option when you log out from the graphical interface, or, when on the login screen (where you have to give your user name and password) look around for a shutdown button.

Now that we know how to connect to and disconnect from the system, we're ready for our first commands.

Graphical Login mode in Linux

abrazaq@gmail.com — Thu, 08 Sep 2011 11:40:00 +0000

This is the default nowadays on most desktop computers. You know you will connect to the system using graphical mode when you are first asked for your user name, and then, in a new window, to type your password.

To log in, make sure the mouse pointer is in the login window, provide your user name and password to the system and click OK or press Enter.

Careful with that root account!

It is generally considered a bad idea to connect (graphically) using the root user name, the system.

Administrator’s account, since the use of graphics includes running a lot of extra programs, in root's case with a lot of extra permissions. To keep all risks as low as possible, use a normal user account to connect graphically. But there are enough risks to keep this in mind as a general advice, for all use of the root account: only log in as root when extra privileges are required.

After entering your user name/password combination, it can take a little while before the graphical environment is started, depending on the CPU speed of your computer, on the software you use and on your personal settings. To continue, you will need to open a terminal window or xterm for short (X being the name for the underlying software supporting the graphical environment). This program can be found in the Applications->Utilities, System Tools or Internet menu, depending on what window manager you are using. There might be icons that you can use as a shortcut to get an xterm window as well, and clicking the right mouse button on the desktop background will usually present you with a menu containing a terminal window application.

While browsing the menus, you will notice that a lot of things can be done without entering commands via the keyboard. For most users, the good old point-'n'-click method of dealing with the computer will do. But this guide is for future network and system administrators, who will need to meddle with the heart of the system. They need a stronger tool than a mouse to handle all the tasks they will face. This tool is the shell, and when in graphical mode, we activate our shell by opening a terminal window.

The terminal window is your control panel for the system. Almost everything that follows is done using this simple but powerful text tool. A terminal window should always show a command prompt when you open one. This terminal shows a standard prompt, which displays the user's login name, and the current working directory, represented by the twiddle (~):

[user@host dir]

In the above example, user will be your login name, hosts the name of the machine you are working on, and dir an indication of your current location in the file system.

To disconnect from the system in graphical mode, you need to close all terminal windows and other applications. After that, hit the logout icon or find Log Out in the menu. Closing everything is not really necessary, and the system can do this for you, but session management might put all currently open applications back on your screen when you connect again, which takes longer and is not always the esired effect. However, this behavior is configurable.

When you see the login screen again, asking to enter user name and password, logout was successful.

Gnome or KDE?

We mentioned both the Gnome and KDE desktops already a couple of times. These are the two most popular ways of managing your desktop, although there are many, many others. Whatever desktop you chose to work with is fine - as long as you know how to open a terminal window. However, we will continue to refer to both Gnome and KDE for the most popular ways of achieving certain tasks.

Characteristics or Properties of Linux

abrazaq@gmail.com — Tue, 06 Sep 2011 07:01:00 +0000

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

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 tele transportation machines or time travel and sell your new code, as long as your customers can still have a copy of that code.

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.

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.

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.

Linux is scalable

From a Palmtop with 2 MB of memory to a petabyte 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.

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.

Is Linux difficult?

abrazaq@gmail.com — Mon, 05 Sep 2011 10:49:00 +0000

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 "lusers" who hadn't seen the light yet. It was common practice to tell a beginning user to "RTFM" (read the manuals). 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.

Linus and Linux

abrazaq@gmail.com — Mon, 05 Sep 2011 10:43:00 +0000

By the beginning of the 90s home PCs were finally powerful enough to run a full blown UNIX. Linus Torvalds, a young man studying computer science at the University of Helsinki, thought it would be a good idea to have some sort of freely available academic version of UNIX, and promptly started to code.

He started to ask questions, looking for answers and solutions that would help him get UNIX on his PC. Below is one of his first posts in comp.os.minix, dating from 1991:

From: torvalds@klaava.Helsinki.FI (Linus Benedict Torvalds)

Newsgroups: comp.os.minix

Subject: Gcc-1.40 and a posix-question

Message-ID: <1991Jul3.100050.9886@klaava.Helsinki.FI>

Date: 3 Jul 91 10:00:50 GMT

Hello netlanders,

Due to a project I'm working on (in minix), I'm interested in the posix standard definition. Could somebody please point me to a (preferably) machine-readable format of the latest posix rules? Ftp-sites would be nice.

From the start, it was Linus' goal to have a free system that was completely compliant with the original UNIX. That is why he asked for POSIX standards, POSIX still being the standard for UNIX.

In those days plug-and-play wasn't invented yet, but so many people were interested in having a UNIX system of their own, that this was only a small obstacle. New drivers became available for all kinds of new hardware, at a continuously rising speed. Almost as soon as a new piece of hardware became available, someone bought it and submitted it to the Linux test, as the system was gradually being called, releasing more free code for an ever wider range of hardware. These coders didn't stop at their PC's; every piece of hardware they could find was useful for Linux.

Back then, those people were called "nerds" or "freaks", but it didn't matter to them, as long as the supported hardware list grew longer and longer. Thanks to these people, Linux is now not only ideal to run on new PC's, but is also the system of choice for old and exotic hardware that would be useless if Linux didn't exist.

Two years after Linus' post, there were 12000 Linux users. The project, popular with hobbyists, grew steadily, all the while staying within the bounds of the POSIX standard. All the features of UNIX were added over the next couple of years, resulting in the mature operating system Linux has become today. Linux is a full UNIX clone, fit for use on workstations as well as on middle-range and high-end servers. Today, a lot of the important players on the hard- and software market each have their team of Linux developers; at your local dealer's you can even buy pre-installed Linux systems with official support - even though there is still a lot of hard- and software that is not supported, too.

Current application of Linux systems

abrazaq@gmail.com — Mon, 05 Sep 2011 10:30:00 +0000

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.

Which distribution should I install?

abrazaq@gmail.com — Mon, 05 Sep 2011 10:21:00 +0000

Prior to installation, the most important factor is your hardware. Since every Linux distribution contains the basic packages and can be built to meet almost any requirement (because they all use the Linux kernel), you only need to consider if the distribution will run on your hardware. LinuxPPC for example has been made to run on Apple and other PowerPCs and does not run on an ordinary x86 based PC. LinuxPPC does run on the new Macs, but you can't use it for some of the older ones with ancient bus technology. Another tricky case is Sun hardware, which could be an old SPARC CPU or a newer UltraSparc, both requiring different versions of Linux.

Some Linux distributions are optimized for certain processors, such as Athlon CPUs, while they will at the same time run decent enough on the standard 486, 586 and 686 Intel processors. Sometimes distributions for special CPUs are not as reliable, since they are tested by fewer people.

Most Linux distributions offer a set of programs for generic PCs with special packages containing optimized kernels for the x86 Intel based CPUs. These distributions are well-tested and maintained on a regular basis, focusing on reliant server implementation and easy installation and update procedures. Examples are Debian, Ubuntu, Fedora, SuSE and Mandriva, which are by far the most popular Linux systems and generally considered easy to handle for the beginning user, while not blocking professionals from getting the most out of their Linux machines. Linux also runs decently on laptops and middle-range servers. Drivers for new hardware are included only after extensive testing, which adds to the stability of a system.

While the standard desktop might be Gnome on one system, another might offer KDE by default. Generally, both Gnome and KDE are available for all major Linux distributions. Other window and desktop managers are available for more advanced users.

The standard installation process allows users to choose between different basic setups, such as a workstation, where all packages needed for everyday use and development are installed, or a server installation, where different network services can be selected. Expert users can install every combination of packages they want during the initial installation process.

The goal of this guide is to apply to all Linux distributions. For your own convenience, however, it is strongly advised that beginners stick to a mainstream distribution, supporting all common hardware and applications by default. The following are very good choices for novices:

· Fedora Core

· Debian and Ubuntu

· SuSE Linux

· Mandriva (former MandrakeSoft)

· Knoppix: an operating system that runs from your CD-ROM, you don't need to install anything.

Redhat Enterprise linux 5 VMware Installation part3

abrazaq@gmail.com — Sat, 03 Sep 2011 09:23:00 +0000

Redhat Enterprise linux 5 VMware Installation part2

abrazaq@gmail.com — Sat, 03 Sep 2011 09:22:00 +0000

Redhat Enterprise linux 5 VMware Installation part1

abrazaq@gmail.com — Sat, 03 Sep 2011 09:14:00 +0000

Linux in The Business

abrazaq@gmail.com — Fri, 02 Sep 2011 15:48:00 +0000

In 2008, IDC analyst Al Gillen cited a nearly 24 percent annual growth rate for the Linux industry, which puts a $21 billion 2007 technology at $49 billion in 2011. The companies involved in Linux include industry leaders such as IBM, Fujitsu, Hewlett-Packard, Oracle, Intel, Hitachi, NEC, and Novell. All have all invested time, talent, and resources to bettering Linux on their own and through the Linux Foundation.

If Linux is free of cost, how does a Linux company generate revenue?

One example of how a Linux business works: while nearly all of a Linux distribution's code is available for free download, the time and cost involved in actually downloading all of that code and putting it together in a cohesive and functional manner is significantly high.

To avoid the timesink and the learning curve required to accomplish such a task, users can simply pay a distribution maker for the convenience of not having to build a free Linux from scratch. Businesses and individual users benefit from the distributors' expertise in putting all of the free Linux code into an easy-to-use set of packages.

Another source of revenue for companies is ongoing commercial support for Linux. In fact, some distributions will allow users to download their software free of charge and build their entire revenue model on a services and support business plan.

Linux is a platform that can generate revenue, all while still being free. Customers gain the knowledge that they are paying directly for support and convenience, and will always have a choice of which Linux systems will work for them best.

Linux Development

abrazaq@gmail.com — Fri, 02 Sep 2011 15:45:00 +0000

Linux is an operating system that is comprised of many different development languages. A very large percentage of the distributions' code is written in either the C (52.86%) or C++ (25.56%) languages. All of the rest of the code falls into single-digit percentages, with Java, Perl, and Lisp rounding out the rest of the top 5 languages.

The Linux kernel itself has an even more dominant C presence, with over 95 percent of the kernel's code written in that language. But other languages make up the kernel as well, making it more heterogenous than other operating systems.

The kernel community has evolved its own distinct ways of operating which allow it to function smoothly (and produce a high-quality product) in an environment where thousands of lines of code are being changed every day. This means the Linux kernel development process differs greatly from proprietary development methods.

The kernel's development process may come across as strange and intimidating to new developers, but there are good reasons and solid experience behind it. A developer who does not understand the kernel community's ways (or, worse, who tries to flout or circumvent them) will have a frustrating experience in store. The development community, while being helpful to those who are trying to learn, has little time for those who will not listen or who do not care about the development process.

While many Linux developers still use text-based tools such as Emacs or Vim to develop their code, Eclipse, Anjuta, and Netbeans all provide more robust integrated development environments for Linux.

Linux in Community

abrazaq@gmail.com — Fri, 02 Sep 2011 15:44:00 +0000

Linux communities come in two basic forms: developer and user communities.

One of the most compelling features of Linux is that it is accessible to developers; anybody with the requisite skills can improve Linux and influence the direction of its development. Proprietary products cannot offer this kind of openness, which is a characteristic of the free software process.

Developer communities can volunteer to maintain and support whole distributions, such as the Debian or Gentoo Projects. Novell and Red hat also support community-driven versions of their products, openSUSE and Fedora, respectively. The improvements to these community distros are then incorporated into the commercial server and desktop products from these companies.

The Linux kernel itself is primarily supported by its developer community as well and is one of the largest and most active free software projects in existence. A typical three-month kernel development cycle can involve over 1000 developers working for more than 100 different companies (or for no company at all).

With the growth of Linux has come an increase in the number of developers (and companies) wishing to participate in its development. Hardware vendors want to ensure that Linux supports their products well, making those products attractive to Linux users. Embedded systems vendors, who use Linux as a component in an integrated product, want Linux to be as capable and well-suited to the task at hand as possible. Distributors and other software vendors who base their products on Linux have a clear interest in the capabilities, performance, and reliability of the Linux kernel.

Other developer communities focus on different applications and environments that run on Linux, such as Firefox, OpenOffice.org, GNOME, and KDE.

End users, too, can make valuable contributions to the development of Linux. With online communities such as Linux.com, LinuxQuestions, and the many and varied communities hosted by distributions and applications, the Linux user base is an often vocal, usually positive advocate and guide for the Linux operating system.

The Linux community is not just a presence online. Local groups known as Linux Users Groups (LUGs) often meet to discuss issues regarding the Linux operating system, and provide other local users with free demonstrations, training, technical support, and installfests.

Redhat Licensing

abrazaq@gmail.com — Fri, 02 Sep 2011 15:42:00 +0000

Code is contributed to the Linux kernel under a number of licenses, but all code must be compatible with version 2 of the GNU General Public License (GPLv2), which is the license covering the kernel distribution as a whole. In practice, that means that all code contributions are covered either by GPLv2 (with, optionally, language allowing distribution under later versions of the GPL) or the three-clause BSD license. Any contributions which are not covered by a compatible license will not be accepted into the kernel.

Copyright assignments are not required (or requested) for code contributed to the kernel. All code merged into the mainline kernel retains its original ownership; as a result, the kernel now has thousands of owners.

One implication of this ownership structure is that any attempt to change the licensing of the kernel is doomed to almost certain failure. There are few practical scenarios where the agreement of all copyright holders could be obtained (or their code removed from the kernel). So, in particular, there is no prospect of a migration to version 3 of the GPL in the foreseeable future.

It is imperative that all code contributed to the kernel be legitimately free software. For that reason, code from anonymous (or pseudonymous) contributors will not be accepted. All contributors are required to "sign off" on their code, stating that the code can be distributed with the kernel under the GPL. Code which has not been licensed as free software by its owner, or which risks creating copyright-related problems for the kernel (such as code which derives from reverse-engineering efforts lacking proper safeguards) cannot be contributed.

Questions about copyright-related issues are common on Linux development mailing lists. Such questions will normally receive no shortage of answers, but one should bear in mind that the people answering those questions are not lawyers and cannot provide legal advice. If you have legal questions relating to Linux source code, there is no substitute for talking with a lawyer who understands this field. Relying on answers obtained on technical mailing lists is a risky affair.