LINUX for Beginners

Linux just for beginners : Linux geeks plz excuse this Physician for his ignorance! its just an attempt to attract few more into Linux.

At this point of time try concentrating being a newbie at Linux.

What is Linux : Lot is heard about it ?

Get a copy of some Linux Distro. Distro ? Yes Linux is not like Windows and lots of flavours of the Linux ice-cream is available for you to taste. These flavors are called "Distro's". So move forward (beg , borrow or steal) and install a popular Distro (First time users should install popular Distros to get less headaches!) like Red Hat, Fedora (Red Hat), SuSE, Mandriva (previously Mandrake) etc. Other Distro's like Debain, Ubuntu, Puppy, Centos can also be checked.,

Installation :
You can install Linux in your existing machine which is having Windows (or other operating system) . The vice-versa ; Installing Windows on a Linux machine is not easy though (it is possible by configuring the bootloader). For beginners the GUI installation is available.. Take care when it asks for the Disk partitioning ; You have to be careful because anything wrong might erase your existing Windows file system. You may get confused about the Swap partition while installation; swap partition should be roughly twice the RAM of your PC.
                     More on the installation later ....

The Console or Terminal  :
Open a terminal/Console > Search anything named terminal in the menu's ; it may appear as "Terminal", "term", "Console" etc. etc. , Clicking it should bring a DOS prompt like window (but don't try DOS here!).

This Terminal is the gate to Linux;The format shown in the terminal is "[user@computer ~]$" .The dollar sign ($) at the end indicates that user is logged in as an normal user and not as root user (SuperUser).
The dollar changes to a hash (#) when the root account is active "[root@computer ~]#".
It is possible to log in as root from a normal login terminal. Use command "su". It will ask for the root password. See example below.



Root is something like Administrator User in Windows, but its does more than that of its Windows counterpart.
           Few System options are only possible when logged in as a "root" user.

Try some commands:

pwd          Present working directory with details

cd /           change directory

clear         Clear screen , simple same as "cls" of MS-DOS.

cp           Copy file from one to different location (same as copy in MS-DOS). e.g. [ritesh@andaman KINGSTON]$ cp linux.txt /home/ritesh

mkdir        Make new directory. e.g. [ritesh@andaman KINGSTON]$ mkdir NEWFOLDER

users        Display list of users currently logged on.

who          Same as "users" but displays usernames.

ls              directory (like dir in MSDOS)

ls */            Listing all contents of sub directory

ls -a           directory listing with hidden files and folders.

ls -l            directory listing with details.



uname -a     Get all details of your Linux kernel.

passwd        Changing user password in Linux.





Finding and searching files in Linux :

whereis          To know about all the possible file locations of the file /package. "whereis php" will return something like "/etc/php.d  /etc/php.ini

find /home/ritesh   To find all the full path of all files inside the folder "ritesh" . See example below in the screenshot.

find /home/ritesh -user ritesh  Its possible to find all files of a particular user (e.g.  "ritesh") in a particular location.

find /home/ritesh -name *admin  The wildcard searching is possible in Linux in the format depicted here. the wildcard *abcd , abcd* and *abcd* is supported.

find /home/ritesh -mtime 7    To find files according to their age ! ; -mtime 21 will display all files in the location which are exactly 21 days old. -mtime +50 will display files more than 50 days old.

rpm -q XXX (where XXX is program) To know if a program package is installed or not. e.g. "rpm -q php" will return something like "php-5.1.2-5" if PHP is installed else it will throw "package PHP is not installed"

chmod          It deals with File and directory permissions and security of files and folders. e.g. chmod 777 ritesh.htm .
                     Given below is the numeric value of permissions:
 

Looking at the table above from where chmod 777 has come ? Interestingly its simple ; 777 means all rights to everyone i.e. All the permissions shown in above table is granted to the file "ritesh.htm". This magic number is acquired by adding all above permissions
            i.e.  400+040+004+200+020+002+100+010+001 = 777 (for your custom file permissions use your permutations and combinations!)