About RED HAT 6

                            Linux Operating system

•It is a system software which provides an interface between user, hardware, peripherals devices and application program. Every os consists of two components

•Kernel

•shell

Kernel

•It is core of an operating system, it is an interpreter between user and hardware. In Dos – 10.sys, msdos.sys, in xp – NTUSKRMI32.com, in linux – Vmlinuz.

•Shell

•Shall is a command line interface (interpreter) between user and kernel. In Dos, winxp, win7,2k8, 2k3, vista – command.com

•In linux and unix – bash, csk,ksh,tcsh.

           Types of operating system

•There are 3 types of operating system.

1.Single user single task – in this os a single user log in an perform a single task

Ex. Dos

2.Single user multitask – in this os include all type of desktop os which log in a single user and perform multitask.

Ex. Xp,win7, ubuntu

3.Multi user multi task – in this os more than one user can log in  from the different terminals and perform multiple task.

Ex. Server 2000,2003, 2008, Redhat Enterprise Linux,etc.                                                               

               File System Structure In Linux

•1. / – Root

•It is a home folder of an administrative account in linux

  Every single file and directory starts from the root directory.

  Only root user has write privilege under this directory.

  2. /bin – User Binaries

•It store all the binaries files

  Contains binary executables.

  Common linux commands you need to use in single-user modes are located under this directory.

  Commands used by all the users of the system are located here.

  For example: ps, ls, ping, grep, cp.

•3. /sbin – System Binaries

•It store all the system binaries

•All the adminsitrative commands such as user add user mode, user del, grp del & grp add etc

  Just like /bin, /sbin also contains binary executables.

•4. /etc – Configuration Files

  Contains configuration files required by all programs.

  This also contains startup and shutdown shell scripts used to start/stop individual programs.

  For example: /etc/resolv.conf, /etc/logrotate.conf

•5. /dev – Device Files

•It is store all the hardware access point .

  Contains device files.

  These include terminal devices, usb, or any device attached to the system.

  For example: /dev/tty1, /dev/usbmon0

•6. /proc – Process Information

•It stores all the virtual file system , process in the system

  Contains information about system process.

  7. /var – Variable Files

  var stands for variable files.

  Content of the files that are expected to grow can be found under this directory.

  This includes — system log files (/var/log); packages and database files (/var/lib); emails (/var/mail); print queues (/var/spool); lock files (/var/lock); temp files needed across reboots (/var/tmp);

•8. /tmp – Temporary Files

  Directory that contains temporary files created by system and users.

  Files under this directory are deleted when system is rebooted.

•9. /usr – User Programs

•It store user documentation and manual pages.

  Contains binaries, libraries, documentation, and source-code for second level programs.

  /usr/bin contains binary files for user programs. If you can’t find a user binary under /bin, look under /usr/bin. For example: at, awk, cc, less, scp

  /usr/sbin contains binary files for system administrators. If you can’t find a system binary under /sbin, look under /usr/sbin. For example: atd, cron, sshd, useradd, userdel

  /usr/lib contains libraries for /usr/bin and /usr/sbin

  /usr/local contains users programs that you install from source. For example, when you install apache from source, it goes under /usr/local/apache2

•10. /home – Home Directories

•It is store the home directory of the local user account with there name .

  Home directories for all users to store their personal files.

  For example: /home/john, /home/nikita

•11. /boot – Boot Loader Files

  it stores booting files of the operating system

  Contains boot loader related files.

  Kernel initrd, vmlinux, grub files are located under /boot

  12. /lib – System Libraries

It store all the library files

  Contains library files that supports the binaries located under /bin and /sbin

  Library filenames are either ld* or lib*.so.*

  For example: ld-2.11.1.so, libncurses.so.5.7

•13. /opt – Optional add-on Applications

  opt stands for optional.

  Contains add-on applications from individual vendors.

  add-on applications should be installed under either /opt/ or /opt/ sub-directory.

•14. /mnt – Mount Directory

  Temporary mount directory where sys admins can mount filesystems.

•15. /media – Removable Media Devices

  Temporary mount directory for removable devices.

  For examples, /media/cdrom for CD-ROM; /media/floppy for floppy drives; /media/cdrecorder for CD writer

•16. /srv – Service Data

  srv stands for service.

  Contains server specific services related data.

  For example, /srv/cvs contains CVS related data.

                                                swap partition

•The swap partition is the portion of the hard drive that linux uses as virtual memory when it runs out of physical memory.

•Swap partition is a dubal of the RAM