Introduction to LINUX Presented By Quontra Solutions

Information about Introduction to LINUX Presented By Quontra Solutions

Published on August 25, 2014

Author: quontra123



Introduction to LINUX: Introduction to LINUX [email protected] Contact:404-900-9988 [email protected] LINUX INTRODUCTION: [email protected] LINUX INTRODUCTION LINUX Is a Unix-like operating system ( OS)created by Linus Torvalds . He developed Linux because he wasn't happy with the currentlyavailable options in Unix and felt he could improve it. So he did what anybody elsewould do, and created his own operatingsystem . [email protected] Kernel : [email protected] Kernel In computing, the kernel is a computer program that manages input/output requests from software, and translates them into data processing instructions for the central processing unit and other electronic components of a computer. The kernel is a fundamental part of a modern computer's operating system . [email protected] linux kernel: [email protected] linux k ernel The Linux kernel is the operating system kernel used by the Linux family of Unix-like operating systems. It is a prominent example of free and open source software. The Linux kernel is released under the GNU General Public License version 2 (GPLv2)(plus some firmware images with various non-free licenses), and is developed by contributors worldwide. https :// 3.10.3 stable version [email protected] LINUX DISTROS: [email protected] LINUX DISTROS A Linux distribution (often called distro for short ) is a member of the family of Unix-like operating systems built on top of the Linux kernel . Such distributions are operating systems including a large collection of software applications such as word processors , spreadsheets, media players, and database applications . [email protected] LINUX DISTROS: [email protected] LINUX DISTROS Popular main distros Debian RedHat Suse Gentoo Slackware * [email protected] LINUX DISTROS: [email protected] LINUX DISTROS Popular child distros Ubuntu ( Debian based ) Fedora ( RedHat ) Centos ( RedHat ) [email protected] Which DISTRO: [email protected] Which DISTRO It depends on Software requirements Team or staff knowledge The one that makes you happy [email protected] uses: [email protected] uses Desktop Phones Tablets TV’s Servers [email protected] how it works?: [email protected] how it works? System startup - BIOS / BootMonitor Stage #1 bootloader (master boot record) Stage #2 bootloader (LILO GRUB) Kernel Init Runlevel [email protected] how it works?: [email protected] how it works? 1 . BIOS BIOS stands for Basic Input/Output System Performs some system integrity checks Searches , loads, and executes the boot loader program. It looks for boot loader in floppy, cd-rom , or hard drive. You can press a key (typically F12 of F2, but it depends on your system) during the BIOS startup to change the boot sequence. Once the boot loader program is detected and loaded into the memory, BIOS gives the control to it. So , in simple terms BIOS loads and executes the MBR boot loader [email protected] how it works?: [email protected] how it works? 2. MBR MBR stands for Master Boot Record. It is located in the 1st sector of the bootable disk. Typically / dev/ hda , or /dev/ sda MBR is less than 512 bytes in size. This has three components 1) primary boot loader info in 1st 446 bytes 2) partition table info in next 64 bytes 3) mbr validation check in last 2 bytes. It contains information about GRUB (or LILO in old systems). So , in simple terms MBR loads and executes the GRUB boot Loader. [email protected] how it works?: [email protected] how it works? 3. GRUB GRUB stands for Grand Unified Bootloader . If you have multiple kernel images installed on your system, you can choose which one to be executed. GRUB displays a splash screen, waits for few seconds, if you don’t enter anything, it loads the default kernel image as specified in the grub configuration file. GRUB has the knowledge of the filesystem (the older Linux loader LILO didn’t understand filesystem ). Grub configuration file is /boot/grub/ grub.conf (/etc/ grub.conf is a link to this). So , in simple terms GRUB just loads and executes Kernel and initrd images . [email protected] how it works?: [email protected] how it works? 4. Kernel Mounts the root file system as specified in the “root=” in grub.conf Kernel executes the / sbin /init program Since init was the 1st program to be executed by Linux Kernel, it has the process id (PID) of 1. Do a ‘ ps - ef | grep init’ and check the pid . initrd stands for Initial RAM Disk. initrd is used by kernel as temporary root file system until kernel is booted and the real root file system is mounted. It also contains necessary drivers compiled inside, which helps it to access the hard drive partitions, and other hardware. Saturday, July [email protected] how it works?: [email protected] how it works? 5. Init Looks at the /etc/ inittab file to decide the Linux run level. Following are the available run levels 0 – halt 1 – Single user mode 2 – Multiuser, without NFS 3 – Full multiuser mode 4 – unused 5 – X11 6 – reboot Init identifies the default initlevel from /etc/ inittab and uses that to load all appropriate program. Execute ‘ grep initdefault /etc/ inittab ’ on your system to identify the default run level If you want to get into trouble, you can set the default run level to 0 or 6. Since you know what 0 and 6 means, probably you might not do that. Typically you would set the default run level to either 3 or 5. [email protected] how it works?: [email protected] how it works? 6. Runlevel When the Linux system is booting up, you might see various services getting started. For example, it might say “starting sendmail …. OK”. Those are the runlevel programs, executed from the run level directory as defined by your run level. • Depending on your default init level setting, the system will execute the programs from one of the following directories. Run level 0 – /etc/ rc.d /rc0.d/ Run level 1 – /etc/ rc.d /rc1.d/ Run level 2 – /etc/ rc.d /rc2.d/ Run level 3 – /etc/ rc.d /rc3.d/ Run level 4 – /etc/ rc.d /rc4.d/ Run level 5 – /etc/ rc.d /rc5.d/ Run level 6 – /etc/ rc.d /rc6.d/ [email protected] how it works?: [email protected] how it works? [email protected] System Requirements : [email protected] System Requirements Desktop 700Mhz processor 512Mb RAM 5Gb hard-drive space VGA 1024x768 CD/DVD or USB port for installer media Internet access (not required but helpful) [email protected] System Requirements : [email protected] System Requirements Server CLI 300Mhz processor 128Mb RAM 1Gb hard-drive space VGA 640x480 CD Thank you: Thank you [email protected] Contact:404-900-9988

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