Operating Systems Lab Manual, Study Guides, Projects, Research of Operating Systems

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18CSC205J - Operating Systems

LAB MANUAL

Bachelor of Technology

Semester IV

Academic Year: 2021-2022 EVEN SEMESTER

FACULTY OF ENGINEERING AND TECHNOLOGY

SRM INSTITUTE OF SCIENCE AND TECHNOLOGY

RAMAPURAM CAMPUS,

CHENNAI- 600 089

Ubuntu installation guidelines in windows

Select Turn Windows features On or Off

Select Windows subsystem for linux then press Ok

Now restart the PC to apply the changes

Choose Microsoft Store and search for Ubuntu and Install it

Now Launch the Ubuntu

Finally you will get the prompt on successful installation of Ubuntu in windows 10 64 bit

LIST OF EXPERIMENTS

Ex.No. Experiment^ Name

1 Understanding the booting process of Linux

2 Understanding^ the^ Linux^ file^ system

3 Understanding^ the^ various^ Phases^ of^ Compilation^ of^ a^ ‗C‘^ Program

4 System^ admin^ commands^ –^ Basics

5 System^ admin^ commands^ –^ Simple^ task^ automations

6 Linux^ commands

7 Shell^ Programs^ –^ Basic^ level

8 Process^ Creation

9 Overlay^ concept

10 Overlay^ concept

11 IPC^ using^ Pipes

12 IPC^ using^ shared^ memory^ and^ Message^ queues

13 Process^ synchronization

14 Study^ of OS

15 Understanding^ the^ OS161^ filesystem^ and^ working^ with^ test^ programs

Step 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.

Step 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).  As you notice from the above info, it contains kernel and initrd image.  So, in simple terms GRUB just loads and executes Kernel and initrd images.

Step 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.

Step 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 – X  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.

Step 6. Runlevel programs

 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. o Run level 0 – /etc/rc.d/rc0.d/ o Run level 1 – /etc/rc.d/rc1.d/ o Run level 2 – /etc/rc.d/rc2.d/ o Run level 3 – /etc/rc.d/rc3.d/ o Run level 4 – /etc/rc.d/rc4.d/ o Run level 5 – /etc/rc.d/rc5.d/ o Run level 6 – /etc/rc.d/rc6.d/  Please note that there are also symbolic links available for these directory under /etc directly. So, /etc/rc0.d is linked to /etc/rc.d/rc0.d.  Under the /etc/rc.d/rc*.d/ directories, you would see programs that start with S and K.  Programs starts with S are used during startup. S for startup.  Programs starts with K are used during shutdown. K for kill.  There are numbers right next to S and K in the program names. Those are the sequence number in which the programs should be started or killed.  For example, S12syslog is to start the syslog deamon, which has the sequence number of 12. S80sendmail is to start the sendmail daemon, which has the sequence number of

80. So, syslog program will be started before sendmail.

Login Process

1. Users enter their username and password
2. The operating system confirms your name and password.
3. A "shell" is created for you based on your entry in the "/etc/passwd" file
4. You are "placed" in your "home"directory.
5. Start-up information is read from the file named "/etc/profile". This file is known as the system login file. When every user logs in, they read the information in this file.
6. Additional information is read from the file named ".profile" that is located in your "home" directory. This file is known as your personal login file.

Outcome: Learned the various stages of Linux boot process.

File System Structure

A file system is a logical collection of files on a partition or disk. A partition is a container for information and can span an entire hard drive if desired. UNIX uses a hierarchical file system structure, much like an upside-down tree, with root (/) at the base of the file system and all other directories spreading from there.

The following table provides a short overview of the most important higher-level directories

you find on a Linux system

Directory Contents / Root directory—the starting point of the directory tree. /bin (^) Essential binary files. Binary Executable files /boot Static files of the boot loader. /dev Files needed to access host-specific devices. /etc (^) Host-specific system configuration files. /lib (^) Essential shared libraries and kernel modules. /media Mount points for removable media. /mnt (^) Mount point for temporarily mounting a file system. /opt (^) Add-on application software packages. /root (^) Home directory for the super user root. /sbin (^) Essential system binaries. /srv (^) Data for services provided by the system.

/proc Contains all processes marked as a file by process number or other information that is dynamic to the system /tmp (^) Temporary files. /usr (^) Secondary hierarchy with read-only data. /var Variable data such as log files /kernal (^) Contains kernel files

EDITORS AND FILTERS

VI EDITOR

 vi fname  to open the file fname

 There are two types of mode in vi editor Escape mode – used to give commands – to switch to escape mode, press key Command mode – used to edit the text – to switch to command mode, press any one the following inserting text command

a) Inserting Text i  insert text before the cursor a  append text after the cursor I  insert text at the beginning of the line A  append text to the end of the line r  replace character under the cursor with the next character typed R  Overwrite characters until the end of the line o  (small o) open new line after the current line to type text O  (capital O) open new line before the current line to type text

b) Cursor movements h  left j  down k up l  right (The arrow keys usually work also)

^ F forward one screen ^ B back one screen ^ D down half screen ^ U up half screen (^ indicates control key; case does not matter)

0  (zero) beginning of line $  end of line

c) Deleting text Note : (n) indicates a number, and is optional

dd  deletes current line (n) dd  deletes (n) line(s) ex. 5dd  deletes 5 lines (n) dw  deletes (n) word(s) D  deletes from cursor to end of line

‗\12‘ Newline ‗\33‘

Ex.

Escape

tr : ‗\11‘ < f1 translates all : into tab of f ile f

-s Option translate multiple occurrences of a character by single character. -d Option is to delete a character

4. grep  Used to search one or more files for a particular pattern.

Syntax : grep pattern filename(s)

Lines that contain the pattern in the file(s) get displayed pattern can be any regular expressions More than one files can be searched for a pattern

-v option displays the lines that do not contain the pattern -l list only name of the files that contain the pattern -n displays also the line number along with the lines that matches the pattern

5. sort  Used to sort the file in order

Syntax : sort filename

Sorts the data as text by default Sorts by the first filed by default

-r option sorts the file in descending order -u eliminates duplicate lines -o filename writes sorted data into the file fname -t dchar sorts the file in which fileds are separated by dchar -n sorts the data as number +1n skip first filed and sort the file by second filed numerically

6. Uniq  Displays unique lines of a sorted file Syntax : uniq filename

-d option displays only the duplicate lines -c displays unique lines with no. of occurrences.

7. cmp  Used to compare two files Syntax : cmp f1 f compare two files f1 & f2 and prints the line of first difference.

8. diff  Used to differentiate two files

Syntax : diff f1 f compare two files f1 & f2 and prints all the lines that are differed between f & f2.

9. comm  Used to compare two sorted files Syntax : comm file1 file

Three columns of output will be displayed. First column displays the lines that are unique to file Second column displays the lines that are unique to file Third column displays the lines that are appears in both the files

-1 option suppress first column -2 option suppress second column -3 option suppress third column -12 option display only third column -13 option display only second column -23 option display only first column

Outcome: Learned and used various Linux file system, file system structure, VI editor and various filter commands in Linux and executed.