TYPE OF BACKUP IN LINUX

INCREMENTAL BACKUP

An incremental backup is a type of backup that only copies files that have changed since the last backup. If a full backup was done on Monday, Tuesday's, incremental will backup files that have changed since Tuesday's incremental backup.

The main advantage of incremental backups is that fewer files are backed up daily, allowing for shorter backup windows. The disadvantages is that during a complete restore, the latest full and all subsequent incremental backups must be restored, which can take significantly longer.

DIFFERENTIAL BACKUP

A differential backup is a type of backup that copies all the data that's been changed since the last full backup. The size of a differential backup grows throughout the week and becomes progressively larger until the next full backup. A full restore from this type of backup only requires the last full backup and the last differential.

COMPARISON BETWEEN INCREMENTAL AND DIFFERENTIAL

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LINUX SHELLS

Shell is any interface through which a user can interact with the computer operating system.

TYPE OF SHELL

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COMMON FILE SYSTEM IN LINUX

File systems are one of the things any newcomer to Linux must become acquainted with. It is a file that organize the data and metadata on a storage device in computer.

EXT2

• This file system is the predecessor to the EXT3 file system.
• EXT2 is not journaled.
• Hence, it is not recommended any longer

EXT3

•  Most popular Linux file system, limited scalability in size and number of files.
• This file system journaled file system that has the greatest use in Linux.
• It is quite robust and quick, although it does not scale well large volumes nor great number of files.
• However, it is still not as scalable as some of the other file systems listed even with htrees.

FAT32

•  FAT32 is the crudest of the file systems listed.
• It is popular with its widespread use and in Windows desktop world. 
• It has made its way into being in the file system in flash RAM devices such as digital cameras, USB memory sticks and etc.
• It has no built in security access control, so is small and works well in these portable and embedded applications.
• It scales the least of the file systems listed and most systems have FAT32 compatibality due to its ubiquity.

GFS

•  The RedHat Global File System was open sourced in mid 2004.
• It is a parallel cluster file system which allows multiple machines to access common data on a SAN (Storage Area Network).
• This important for allowing multiple machines access to the same data to ease management such as common configuration files between multiple webservers.
• It also allows applications and services which are written to direct disk access to be scaled out to multiple nodes.

JFS

•  The IBM Journaled File System is the file system used by IBM in AIX and OS/2.
• It is a feature rich fie system ported to Linux to allow for ease of migration of existing data.
• It has been shown to provide excellent overall performance across a variety of workloads.

ReiserFS

•  The Reiser File System is the default file system in SUSE Linux distributions.
• It was designed to remove the scalability and performance limitations that exist in EXT2 and EXT3 file systems.
• It scales and performs extremely well on Linux, outscalling EXT3 with htrees.
• It is the best file system on Linux where there are a great number of small files in the file system.

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TYPE OF BOOT LOADERS IN LINUX

GRUB

• GNU GRUB short for GNU Grand Unified Bootloader.
• Reference implementation of the Multiboot Specification, which provides a user the choice to boot one of multiple operating system installed on a computer or select a specific kernel configuration available on a particular operating system's partitions 
• Features 
• - user can dynamically configure the GRUB sub-syste.
• - GRUB is highly portable and can be used in a variety of different user interfaces.
• - it can download operating-system images from a network and can support operating system that do not multi-boot.

LOADLIN

•  Loadlin is a Linux boot loader that runs under DOS or Microsoft Windows.
• Loadlin and the Linux kernel are both files on a file system accessible to DOS/Windows.
• It loads the Linux kernel into memory from a file. It also places various configuration parameters into memory and transfers control to the kernel. 
• The kernel reads these parameters, initializes and runs, replacing DOS/Windows completely.

 LILO

•  LILO was default boot loader for most Linux distributions in the years after the popularity of loadlin.
• LILO is a boot loader for Linux/x86 and other PC operating systems.
• It is responsible for loading your Linux kernel from either a floppy or a hard drive and passing control to it.
• It is capable of booting beyond cylinder 1024 of a hard disk if the BIOS supports EDD packet call extensions to the int 0x13 interface.
• LILO can also be used to boot many other operating systems, including DOS, Windows (all versions), OS/2, and the BSD variants
• The LILO distribution includes full source, documentation and support files.

SYSLINUX

• The Syslinux Project is suite of lightweight IBM PC MBR bootloaders for starting up computers with the Linux kernel.
• It normally used for booting full Linux installations since Linux is not normally on FAT file systems.
• Instead, it is often used for boot rescue floppy disks, USBs or other lightweight boot systems.
• Syslinux also presents a simple text interface that can be used to select between configurations defined in the configuration file and can be used to add parameters to the kernel.
  

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METHOD OF LINUX INSTALLATION

1. DVD/CD ROM

•  For this method, user need to have a DVD/CD ROM drive and the CD installation.
• User can download the official release Linux iso image from whatever distributions they choose from distribution's official website and burn it into cd or dvd.
• They also have many mirrors in regions around the world which provide cd and dvd iso image download using FTP or HTTP for faster download.

2. Hard Drive

• User need to transfer the set of Scientific Linux Installation CD iso images to adirectory on their hard drive. Be sure to do amd5sum on the iso's. It is to ensure the user downloaded properly.
•  Be usre to keep track of what drive, partition and directory on that you have your iso images. 

3. NFS (Network File System)

• If you need to install Linux on many machines, you can use NFS . It makes it easier and faster because it allows you to install Linux on your local network.
• However, you need to configure the NFS server in order to make it available to remote machines.

4. FTP

• You can use this method if you don't have Red Hat Linux CD-ROM or a CD-ROM drive but do have network access.
• When installing via FTP, the Red Hat Linux packages you select are downloaded (using FTP) across the network to your computer and are installed on your hard drive.

5.HTTP

•  Select this option if you have a HTTP (web) or FTP server that you can install from.
• If you have a web server running and want to enable HTTP access to your install server then add sym links from your document root to the install server directory and this will grant access.
• Then, make the install directory visible to your web server by making it appear under the document root by some means.

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REASONS TO MAKE PARTITION

Partitioning is the act of dividing a hard disk drive into multiple logical storage units referred to as partiotions, to treat one physical disk drive as if it were multiple disks. Partitions are also termed "slices" for operating systems based on BSD, Solaris or GNU Hurd. A partition editor software program can be used to create, resize, delete and manipulate these partitions on the hard disk.

There are some of the reasons to make partition.

• Easy to manage
  If you keep your operating system and applications on a partition separate from your data, the data will be more easier to back up and easier to restore. Its make your system more manageable. Another more, if you need to reinstall the operating system, you can do it without worrying about the data on the other partition.
   
• Backup and Recovery
  You can store a complete backup image (an exact clone/duplicate) of your whole Windows installation on a second partition. This can be used quickly restore Windows in the event of major problems without losing anything, so your settings, programs and Windows would be the same as at the time you created the backup. It also make it easier to recover a corrupted file system or operating system installation.


• Security
  Separation of the operating system files from user files may result into a better and secure system. Restrict the growth of certain file systems is possible using various techniques.
   
• Secure the data from virus / data crash
  Viruses and malware target files on the main Windows C: partition. If your document are stored there, they are much more likely to become infected than if they are stored in a separate D: partition. So if part of your hard drive becomes corrupted or infected with virus or malware, the other partitions have a good  chance of remaining unscathed.
   
•  Different file system
  By creating the partition and separate the system files and user files into a different file system, it may decrease the chance of corruption or accidental deletion of crucial system files.
  
  
• Multi Operating System
  For creating multiple operating system boots sequences. Different partitions can be used for different operating systems like Windows, Linux and other else.
   
• Squeeze more performance
  Partitioning a large drive into smaller units improves performance by decreasing the amount of traveling the drive's read/write head has to do when it searches for data. A partition also shrinks the size of the tables the computer uses to keep track of where dara is stored, further improving performance.
   
• Stability and Efficiency
  You can increase disk space efficiency by formatting disk with various block sizes. It depends upon the usage.

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KERNEL (MONOLITHIC KERNEL AND MICROKERNEL)

Kernel is a program that constitutes the central core of  a computer operating system. It has complete control over everything that occurs in the system. A kernel can be contrasted with a shell, which is the outermost part of an operating system and a program that interacts with user commands.

Monolithic

A monolithic kernel is an operating system architecture where the entire operating system is working in the kernel space and alone as supervisor mode. The monolithic differs from other operating system architectures (such as the microkernel architecture) in that it defines alone a high-level virtual interface over computer hardware, with a set of primitives or system calls to implement all operating system services such as process management, concurrency, and memory management itself and one or more device drivers as modules.

Properties of Monolithic Kernels

• OS is all in one place, below the “red line”

• Applications use a well-defined system call interface to interact with kernel

• Examples:  Unix, Windows NT/XP, Linux, BSD, OS/161

• Common in commercial systems

Advantages and disadvantage

Microkernel

Microkernel is the only software executing at the most privileged level (generally referred to as supervisor or kernel mode).[citation needed] Traditional operating system functions, such as device drivers, protocol stacks and file systems, are removed from the microkernel to run in user space.[citation needed] In source code size, microkernels tend to be under 10,000 lines of code, as a general rule. MINIX's kernel, for example has less than 6,000 lines of code.

 

Properties of Microkernels

• Design Philosophy:  protected kernel code provides minimal “small, clean, logical” set of abstractions

• Tasks and threads

• Virtual memory

• Interprocess communication

• Everything else is a server process running at user-level

• Examples: Mach, Chorus, QNX, GNU Hurd

• Mixed results

Microkernel Advantages and disadvantage

 

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