System Administrator Responsible for? Install OS Network Configuration Security Configuration Patching Backup Performance Management Storage Management User Management TroubleShooting & Maintainance Vendor Management Created by

Who You Work with Sys Admin Network Team Storage Admin Backup Admin Database Admin Security Team Application Team Noc/Help Desks FacilitiesVendors Created by

Operating System [OS] OSUnixAIX(IBM)HPUX Oracle Solaris LinuxRedhatSuseDebainUbuntuMintWindows Created by betwn Unix and LinuxDiff mac linHow many linux distro Most Popular LinuxPopular linux by catogery Another link diff unix and linux

Environment Development or sandboxing Development Environment Integration, developer testing and side effects Test Environment Performance testing, quality Assurance, Check if there is any negative impact on the existing functionality QA Environment Pre-production environment Final testing prior to deploying to production Staging Environment Serves end- users/clients Production Environment Created by

Severity Level Severity 1 (urgent) :Severity 2(High):Severity 3(Medium):Severity 4(Low): Created by Link to severity Level Red Hats version of severity Level

What is Operating System A software program designed to act as an interface between a hardware and the user. It controls the hardware, manages system resources and supervises interaction between the system and its users.

OS User Shell kernel Hardware

Kernel Kernel : Core of the Unix OS. It interacts with the hardware. It is loaded into memory when the system is booted. Its functions are -the kernel is responsible for memory management, process and task management, and disk management.processtaskdisk -The kernel connects the system hardware to the application software

Shell Simply put, the shell is a program that takes your commands from the keyboard and gives them to the operating system to perform. In the old days, it was the only user interface available on a Unix computer. Nowadays, we have graphical user interfaces (GUIs) in addition to command line interfaces (CLIs) such as the shell. On most Linux systems a program called bash (which stands for Bourne Again SHell, an enhanced version of the original Bourne shell program, sh, written by Steve Bourne) acts as the shell program. There are several additional shell programs available on a typical Linux system. These include: ksh, tcsh and zsh.bashkshtcshzsh

What is the difference between a kernel and shell? What happens if we have ONLY the kernel BUT NO shell? You then have a machine with the actual OS but there is NO way you can use it. There is no "interface" for the human to interact with the OS and hence the machine. (Assuming GUIs don't exist, for simplicity :) What happens if we have ONLY the shell BUT NO kernel? This is impossible. Shell is a program provided by the OS so that you can interact with it. Without the kernel/OS nothing can execute (in a sense, not 100% true though, but you get the idea) A shell is just a program that offers some functionality that runs on the OS. The kernel is the "essence/core" of the OS. The words can be confusing so here's the dictionary definition of kernel: [code]Kernel: a softer, usually edible part of a nut, seed, or fruit stone contained within its hard shell.[/code] See how the words kernel/shell relate? That's the origin of it and its borrowed use in computing. The kernel is the essence/core of the OS. You access the machine via the OS and the OS via a "shell" that seems to "contain" the kernel. Kernel and Shell

Linux Operating System

Kernel

Shell Bourne Shell (sh) -- This shell does not have the interactive facilities provided by modern shells such as the C shell and Korn shell. C Shell (csh) -- It provides a C-like language with which to write shell scripts - hence its name. Korn Shell (ksh) -- It provides all the features of the C and TC shells together with a shell programming language similar to that of the original Bourne shell. Bash Shell(bash) -- Bash provides all the interactive features of the C shell (csh) and the Korn shell (ksh). Its programming language is compatible with the Bourne shell (sh).

PATH Absolute Path:-> An absolute path is defined as the specifying the location of a file or directory from the root directory(/). In other words we can say absolute path is a complete path from start of actual filesystem from / directory. Eg: /var/ftp/pub Relative Path:-> Relative path is defined as path related to the present working directory(pwd). Suppose I am located in /var/log and I want to change directory to /var/log/kernel. I can use relative path concept to change directory to kernel.Eg: pwd /var/log cd kernel Absolute Path vs Relative PathGood link for PathsVideo link for Paths

UseFul commands

Directory Layout FileSystem Layout

Logical Volume 500MB Logical Volume 1GB /dev/appvg Volume Group 20GB Physical Partition pvcreate /dev/sdb1 Physical Partition pvcreate dev/sdb2 /dev/sdb Physical Hard Drive fdisk /dev/sdb 20 GB /dev/sdb1 10 GB/dev/sdb2 10GB vgcreate appvg /dev/sdb1 /dev/sdb2 Lvcreate –L 500 –n datalv appvg mkfs.ext4 /dev/appvg/datalv Lvcreate –L 1024 –n sharelv appvg mkfs.ext4 /dev/appvg/sharelv lvextend –L +500 /dev/appvg/datalv free 18.5 GB resize2fs /dev/appvg/datalv Logical Volume (pvcreate) Volume group (vgcreate) Logical volume (lvcreate) mount –t ext4 /dev/appvg/datalv /data mount –t ext4 /dev/appvg/sharelv /share Mount point /data Mount point /share