Unix and System Booting Overview

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Questions and Answers

What does the task_struct data structure NOT contain?

Processes priority

Timing information (correct)

Process state

Error number of the last faulting system call

What is the maximum size of the kernel process table in Linux?

256 entries

1024 entries

2048 entries

512 entries (correct)

What is the Process ID (PID) of the init process?

1 (correct)

Which of the following accurately describes the init process?

It is the ultimate parent in the running system. Signup and view all the answers

Which of the following is NOT a valid process state represented in task_struct?

Sleeping Signup and view all the answers

What is the primary function of the BIOS during the boot process?

To connect hardware and software Signup and view all the answers

Which hexadecimal address does the CPU begin executing at during the startup process?

0XFFFFFFF0 Signup and view all the answers

What does the term POST stand for in the context of computer booting?

Power-On Self Test Signup and view all the answers

What is the role of EEPROM in relation to BIOS?

It stores the BIOS code Signup and view all the answers

What interface does the BIOS provide for the operating system?

Hardware Interface Signup and view all the answers

What boot procedure is followed by Red Hat Enterprise Linux 6.0?

Upstart procedure Signup and view all the answers

During the boot process, how does the BIOS communicate with hardware components?

Through standardized calls Signup and view all the answers

How does the BIOS interact with USB devices on newer motherboards?

It identifies and recognizes them Signup and view all the answers

What is one of the main functionalities that students will learn about in this module?

Manipulating user accounts Signup and view all the answers

Which aspect of process management is included in this module?

PS tool Signup and view all the answers

What role does Unix primarily play according to the context provided?

It serves as a foundational example for many operating systems Signup and view all the answers

Which statement accurately describes the historical significance of Unix?

It has contributed significantly to the development of the Internet. Signup and view all the answers

What does the security aspect of this module address?

Basic UNIX and Linux security issues Signup and view all the answers

Which of the following best describes the evolution of Unix mentioned in the content?

It started as a test platform and evolved to power numerous devices. Signup and view all the answers

What is a key feature of Unicode mentioned in the content?

It has replaced ASCII and other character encoding systems. Signup and view all the answers

Which of the following operating systems is Unix derived from?

Apple's iOS Signup and view all the answers

What does the command 'shutdown -r now' accomplish?

It reboots the system immediately. Signup and view all the answers

Which of the following options is NOT a valid use of the shutdown command?

shutdown -x 12:00 Signup and view all the answers

What is the purpose of the 'kill' command in UNIX?

To terminate a specified process or process group. Signup and view all the answers

What information is NOT included in the /etc/passwd file format?

User's email address Signup and view all the answers

What does the 'x' character in the password field of /etc/passwd indicate?

The password is stored in /etc/shadow. Signup and view all the answers

Which User ID (UID) is reserved for the root user?

0 Signup and view all the answers

What is the maximum character limit for a username in the /etc/passwd file?

32 characters Signup and view all the answers

What does the option '-f' do when used with the shutdown command?

Performs a fast reboot without checking the file system. Signup and view all the answers

What does the stage one bootloader search for on a Windows system?

A partition marked as ‘active’ Signup and view all the answers

How many partitions can be marked as active on a correctly created MBR disk?

One Signup and view all the answers

What is the maximum size of the boot code that can be loaded by the MBR?

512 bytes Signup and view all the answers

What is LILO in the context of boot loaders?

A boot loader that can load multiple images Signup and view all the answers

Where can LILO be placed on a computer system?

In the MBR or boot sector partition Signup and view all the answers

What is the role of the boot loader?

To load the kernel into memory Signup and view all the answers

What is the /dev/initrd file classified as?

Read-only block device Signup and view all the answers

Which component of the boot process is independent of the operating system?

Boot loader Signup and view all the answers

Study Notes

Unix History

Unix is a foundational operating system, influencing modern systems such as Linux, Apple's OS X, Android, and iOS.
Unix is based on principles that are universally applicable and not bound by a specific operating system.
Unix is widely used in infrastructure, the Internet, consumer desktops and laptops, mobile devices, TVs, home routers, and supercomputers.

Encoding

Unicode now replaces ASCII, ISO 8859, and EUC.
Users can handle practically any script and language used on the planet.
Supports comprehensive set of mathematical and technical symbols to simplify scientific information exchange.
UTF-8 is the way in which Unicode is used under UNIX, Linux, and other systems.

Booting the Machine

The startup process is the installation of software.
The boot up procedure utilized by Linux, HP-UX UNIX, and Solaris are based on the UNIX System V procedure.
Red Hat Enterprise Linux 6.0 boot up procedure is based on the Upstart procedure.

BIOS

The BIOS is the lowest level of software that interfaces with the hardware as a whole.
BIOS code is inside a chip on the motherboard of your PC, usually stored on what is called an EEPROM.
The BIOS interface allows the bootloader and operating system kernel to communicate with and control the hardware.
The BIOS on newer motherboards recognizes and identifies USB devices, external drives, and USB mice.

Boot Loader

The boot loader is responsible for loading the kernel into memory.
Boot loaders are independent of the operating system.
The boot loader must share the 512 bytes with the partition table.
The boot loader searches for a partition marked as "active" which indicates that the start of the partition contains the next portion of the boot code in its starting sectors.
On a correctly created MBR disk, only one partition can be marked as active at a time.

LILO

The LILO is independent of specific file systems, allowing it to boot an operating system from floppy disks and hard drives.
LILO can be placed either in the master boot record (MBR) or the boot sector partition.

Linux Initrd

The /dev/initrd file is a read-only block device.

Linux Kernel Data Structure (task_struct)

The task_struct data structure contains the following fields:
- Process state
- Processes priority
- Clock ticks
- Error number of the last faulting system call

Processes

Processes have the following:
- Original parent
- Parent
- Youngest child
- Younger sibling
- Older sibling
Processes have timing information, such as the amount of time the process has spent in user mode.

Linux Kernel Process Table

The kernel process table is implemented as an array of pointers to task structures.
The kernel process table is limited in size to 512 entries.

Role of the init process

The init process is the ultimate parent in the running system.
The init process has a Process ID (PID) of one (1) and a Parent Process ID of zero (0).
The init process plays an important role in the startup process.
All future processes on the system are descendants of the init process.
Once the system processes are created, then the kernel's work is basically completed.

Shutdown Command

The shutdown command shuts down a system immediately - shutdown -h now
The shutdown command reboots a system immediately - shutdown -r now
Users can specify an exact time or a delay before shutdown.
shutdown -h 20:00 will turn the computer off at 8:00 PM.
shutdown -r -t 60 will automatically reboot the machine within 60 seconds (one minute) of issuing the command.

Kill Command

The kill command sends the specified signal to the specified process or process group.
Avoid indiscriminate use of the kill command on jobs involving text editors, databases, mail programs, or any other program that has a large amount of user interaction.

/etc/passwd File

Located in /etc/passwd
Field separators: Colon (:)
File format: Username:Password:UID:GID:UserID:Home directory:Command/shell
Example: dandrear:x:1020:1021:dandrear user:/export/home/dandrear:/bin/bash

/etc/passwd Fields

Username: Used when a user logs in. The username should be between 1 and 32 characters in length.
Password: An "x" character indicates that the encrypted password is stored in the /etc/shadow file.
User ID (UID): Each user must be assigned a user ID (UID). UID 0 (zero) is reserved for root and UIDs 1-99 are reserved for other predefined accounts.
Group ID (GID): The primary group ID (stored in /etc/group file)
User ID Info: The comment field. This field is user defined and can hold information like the user's full name, phone number, etc.

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Description

This quiz covers the history of Unix as a significant operating system and its influence on modern systems. Additionally, it delves into encoding standards, the booting processes of various systems, and the role of BIOS. Test your knowledge on these essential computing concepts!