unit 4

sudo (short for "superuser do") is a command in Unix-like operating systems that allows authorized users to execute commands as the superuser or another user, as specified by the system's security policy. It provides a way to perform administrative tasks and run privileged commands while maintaining a separation between regular user privileges and administrative privileges.

Key features of sudo:

Authorization: sudo is typically configured to allow specific users or groups to execute commands with elevated privileges.
Command Logging: sudo can log all executed commands, providing an audit trail for system administrators.
Time-based Controls: It can be configured to restrict the duration of elevated privileges, enhancing security.
Fine-Grained Control: Administrators can specify which commands users can run with sudo and which commands require full root access.

sudo is commonly used in Linux distributions to execute administrative tasks, such as software updates, system configuration changes, and file management operations, without the need to log in as the root user.

Root Account: The root account, often referred to as the superuser or the administrator, is a special user account in Unix-like operating systems that has unrestricted access to all system resources and commands. The root user can perform any action on the system, including modifying system files, installing software, and configuring system settings. Due to its broad privileges, it is crucial to use the root account with caution to avoid accidental system damage or security risks.

Logging in as the root user is generally discouraged for routine tasks because it exposes the system to potential security vulnerabilities. Instead, it's recommended to use sudo to execute specific commands with elevated privileges when needed. However, if you must log in as the root user, you can do so with the following procedure:

Procedure to Login as Root User (Temporary):

Open a terminal.
Type the following command and press Enter:
```
sudo -i
```
You will be prompted to enter your user password.
After entering the correct password, you will be granted a root shell, and your command prompt will change to indicate that you are now the root user.

Example:
```
root@hostname:~#
```
Be cautious when performing actions as the root user, as you have full control over the system, and mistakes can have significant consequences.
To exit the root shell and return to your regular user account, simply type exit and press Enter:
```
exit
```

2.What are roles and responsibilities of a Linux administrator in Linux system?

A Linux system administrator, often referred to as a sysadmin, plays a crucial role in managing and maintaining Linux-based systems. The roles and responsibilities of a Linux administrator can vary depending on the organization's size, specific needs, and the complexity of the systems they are responsible for.

1. System Installation and Configuration:

Install, configure, and maintain Linux operating systems on servers, workstations, and virtual machines.
Perform system initialization and setup, including partitioning, file system creation, and network configuration.

2. User and Group Management:

Create, modify, and delete user accounts and groups.
Manage user access and permissions, including setting up user roles and privileges.

3. Security Management:

Implement and maintain security measures, such as firewalls, intrusion detection systems, and security updates.
Perform regular security audits and vulnerability assessments.
Enforce access controls and authentication mechanisms.

4. System Updates and Patch Management:

Keep the system up to date by applying patches, updates, and security fixes.
Configure and manage package repositories and package managers (e.g., YUM, APT).

5. Backup and Recovery:

Set up backup systems and routines to ensure data integrity and availability.
Develop disaster recovery plans and procedures.

6. File System Management:

Manage file systems, including creating, mounting, and resizing partitions.
Monitor disk space usage and implement storage solutions as needed.

7. Performance Monitoring and Optimization:

Monitor system performance using tools like top, vmstat, and sar.
Optimize system resources, including CPU, memory, and disk space.

8. Service and Application Management:

Install, configure, and manage software applications and services.
Monitor and troubleshoot application issues.

9. Network Configuration and Management:

Configure and manage network interfaces, IP addresses, and routing tables.
Troubleshoot network connectivity problems.

10. Scripting and Automation: - Write scripts (e.g., Bash, Python) to automate routine tasks and system administration processes. - Implement and manage task scheduling (e.g., cron jobs).

11. Troubleshooting and Problem Resolution: - Identify and resolve system-related issues, including hardware and software failures. - Analyze system logs and error messages.

12. Disaster Recovery and Business Continuity: - Develop and maintain disaster recovery plans to ensure system availability in case of failures or disasters.

13. Documentation: - Create and maintain system documentation, including configuration files, procedures, and network diagrams.

14. Security Policy Implementation: - Enforce security policies, access controls, and best practices across the organization. - Conduct security audits and implement security measures.

15. Collaboration and Communication: - Collaborate with other IT teams, developers, and stakeholders to meet organizational goals. - Provide technical support and guidance to end-users.

16. Continuous Learning: - Stay up to date with Linux technologies, security practices, and industry trends. - Pursue relevant certifications to enhance skills and knowledge.

17. Compliance and Governance: - Ensure that the Linux systems comply with industry regulations and organizational policies.

3.What is a root user? Explain the methods to monitor system performance in Linux Environment with example.

The root user, also known as the superuser, is a special user account in Unix-like operating systems, including Linux, that has full administrative privileges and unrestricted access to all system resources and commands. The root user has the highest level of authority on the system and can perform any action, including system configuration, software installation, and file manipulation.

Here are some key characteristics of the root user:

Unrestricted Access: The root user can execute any command and access any file or directory on the system, bypassing normal access controls and permissions.
Responsibility: With great power comes great responsibility. The root user is responsible for the overall system's integrity, security, and stability. Therefore, it should be used judiciously and only when necessary.
Security Risk: Because of its extensive privileges, the root user account is a potential security risk. Misuse or unauthorized access to the root account can lead to system compromise or data loss.

Methods to Monitor System Performance in Linux:

Monitoring system performance is crucial for maintaining the stability and efficiency of a Linux system. Linux provides various tools and utilities to monitor system performance, track resource usage, and diagnose issues. Here are some common methods and tools to monitor system performance:

1. top Command:

The top command provides real-time information about system performance, including CPU usage, memory usage, running processes, and system load.
Open a terminal and run top to launch the top utility. Here's an example:
```
top
```
top continuously updates the display, allowing you to monitor resource usage interactively. Press 'q' to exit.

2. htop Command:

htop is an interactive process viewer and system monitor that offers an enhanced and more user-friendly version of top. It provides a visual representation of system performance.
Install htop if it's not already available on your system and run it:
```
sudo apt-get install htop  # On Debian/Ubuntu
htop
```

3. vmstat Command:

The vmstat command provides system-wide statistics on processes, memory, paging, block I/O, and CPU activity.
Run vmstat with the desired interval and count to display periodic updates:
```
vmstat 1 5  # Display statistics every 1 second, 5 times
```

4. sar Command:

The sar command (System Activity Reporter) collects, reports, and saves system activity information, including CPU, memory, and disk usage.
Install sar if needed and run it to display system performance data:
```
sudo apt-get install sysstat  # On Debian/Ubuntu
sar
```

5. iostat Command:

The iostat command reports CPU and input/output statistics for devices, partitions, and network filesystems (NFS).
Run iostat with the desired options to monitor disk and CPU activity:
```
iostat -d 1 5  # Display disk statistics every 1 second, 5 times
```

6. free Command:

The free command provides information about system memory and swap usage.
Running free -m will display memory usage in megabytes:
```
free -m
```

4.What is Kudzu? What are the module configurations commands? Explain with example of each.

Kudzu was a hardware detection and configuration tool used in some Linux distributions, particularly in the past. Its primary purpose was to identify and configure hardware devices, such as network cards, sound cards, and storage controllers, during the system's boot process or when new hardware was detected.

Kudzu performed the following tasks:

Hardware Detection: It detected and identified hardware devices connected to the system.
Driver Loading: It attempted to load the appropriate device drivers for the detected hardware.
Configuration: Kudzu configured the detected devices, making them available for use by the operating system.

Here are some example module configuration commands related to hardware management in Linux:

1. modprobe Command:

The modprobe command is used to add and remove kernel modules (device drivers) dynamically.
To load a module (driver), use the following syntax:
```
sudo modprobe module_name
```
Replace module_name with the name of the module you want to load.
Example: Loading the snd-pcm module for sound support:
```
sudo modprobe snd-pcm
```

2. lsmod Command:

The lsmod command lists the currently loaded kernel modules.
To view the list of loaded modules, simply run:
```
lsmod
```

3. rmmod Command:

The rmmod command is used to remove (unload) a loaded kernel module.
To unload a module, use the following syntax:
```
sudo rmmod module_name
```
Replace module_name with the name of the module you want to unload.
Example: Unloading the snd-pcm module:
```
sudo rmmod snd-pcm
```

4. lsusb and lspci Commands:

These commands are used to list USB devices (lsusb) and PCI devices (lspci) connected to your system, respectively.
Running these commands provides information about detected hardware devices and their associated drivers.
Example: Listing USB devices:
```
lsusb
```
Example: Listing PCI devices:
```
lspci
```

5. What is root account and root directory? How can you switch user in Linux from terminal? Also explain the importance of sudo command.

The root account in Linux is a special user account that has superuser or administrative privileges. It is often referred to as the "root user" or "superuser." The root account can perform any action, including system configuration, software installation, and file manipulation.

Key characteristics of the root account:

Unrestricted Access: The root account can execute any command and access any file or directory on the system, bypassing normal access controls and permissions.
Responsibility: With great power comes great responsibility. The root user is responsible for maintaining the system's integrity, security, and stability. It should be used judiciously and only when necessary.
Security Risk: Because of its extensive privileges, the root account is a potential security risk. Misuse or unauthorized access to the root account can lead to system compromise or data loss.

Root Directory: The term "root directory" in Linux refers to the top-level directory in the file system hierarchy. It is denoted by the forward slash character ("/"). The root directory contains all other directories and files on the system, forming the basis of the file system structure. Every file and directory on a Linux system is located within or beneath the root directory.

For example, some important directories within the root directory include:

/etc: Contains system-wide configuration files and scripts.
/home: Typically contains user home directories.
/var: Contains variable data, such as log files and spool directories.
/tmp: Contains temporary files.

Switching User in Linux from the Terminal: In Linux, you can switch between users from the terminal using the su (switch user) command. To switch to another user's account, including the root account, follow these steps:

Open a terminal.
To switch to a specific user, use the following command, replacing username with the target username:
```
su username
```
You will be prompted to enter the password for the target user.
If you want to switch to the root user, you can use su without specifying a username:
```
su
```
You will be prompted to enter the root user's password.
After successfully entering the password, you will be logged in as the specified user or the root user. The terminal prompt will change to indicate the current user.

Importance of the sudo Command: The sudo (superuser do) command is of great importance in Linux for the following reasons:

Elevated Privileges: sudo allows authorized users to execute commands with elevated privileges, such as those of the root user, without needing to log in as the root user. This helps maintain a separation between regular user privileges and administrative privileges.
Security: Using sudo is more secure than directly logging in as the root user because it requires users to enter their own passwords, not the root user's password. It also logs command execution, providing an audit trail.
Granular Control: System administrators can configure sudo to grant specific users or groups access to specific commands or scripts, ensuring fine-grained control over who can perform administrative tasks.
Reduced Risk: By using sudo, users are less likely to accidentally execute harmful commands or make system-altering mistakes since they need to explicitly request elevated privileges.
Best Practice: It is considered a best practice in Linux system administration to use sudo for administrative tasks instead of relying on the root account. This approach helps minimize the risk of security breaches and system errors.

6. What is role of super user in linux?

The superuser, often referred to as the "root user" or simply "root," plays a central and critical role in the Linux operating system. The role of the superuser is as follows:

Administrative Privileges: The superuser has the highest level of authority on a Linux system and possesses unrestricted access to all system resources, files, and commands. This means that the superuser can perform any action on the system, including system configuration, software installation, and file manipulation.
System Maintenance: The superuser is responsible for maintaining the integrity, security, and stability of the Linux system. This includes tasks such as configuring hardware, setting up system services, managing users and groups, and ensuring system updates are applied.
Security: The superuser is responsible for enforcing security measures and access controls on the system. This involves configuring firewalls, intrusion detection systems, and access permissions to safeguard the system from unauthorized access and potential threats.
Software Installation: The superuser is the only user who can install system-wide software packages and updates. This ensures that software installations do not compromise system integrity or interfere with other users.
Configuration: Many system configuration files and settings can only be modified by the superuser. This includes critical configuration files in the /etc directory, which control various aspects of system behavior.
Maintenance and Troubleshooting: The superuser is the go-to account for resolving system issues and errors. It is used to diagnose and fix problems, analyze system logs, and perform system recovery tasks.
Access Control: The superuser has the ability to create, modify, and delete user accounts and groups, as well as set permissions for files and directories. This allows for centralized access control management.
Emergency Recovery: In the event of a system malfunction or data loss, the superuser can take corrective actions to recover the system and data, such as restoring backups or repairing filesystems.
System Updates: The superuser is responsible for applying system updates, security patches, and software upgrades to keep the system secure and up to date.
Customization: System customization and fine-tuning, including kernel parameter adjustments and system optimizations, are often performed by the superuser.

7. What do you mean by shadow password file? Explain how you can make your password more secure and stronger?

A shadow password file is a system file used in Unix-like operating systems, including Linux, to enhance the security of user account passwords. It contains the hashed or encrypted passwords of user accounts, as well as other related information. The purpose of a shadow password file is to separate the sensitive password information from the main password file (typically /etc/passwd), which is accessible to all users. By doing this, it adds an extra layer of security to user account information.

Here's how a shadow password file works and why it's important:

Main Password File (/etc/passwd): The main password file traditionally contained user account information, including usernames, user IDs (UIDs), group IDs (GIDs), and password hashes. However, storing password hashes in a file that was readable by all users posed a security risk, as attackers could potentially access and attempt to crack the passwords.
Shadow Password File (/etc/shadow): To address this security concern, the shadow password file was introduced. The shadow password file stores the password hashes, as well as other password-related information (e.g., password expiration dates and account lockout policies). This file is restricted to system administrators and is typically not accessible to regular users.

To make your passwords more secure and stronger, consider the following best practices:

Use Complex Passwords: Create passwords that are difficult to guess by including a combination of uppercase letters, lowercase letters, numbers, and special characters. Avoid using easily guessable passwords like "password" or "123456."
Password Length: Longer passwords are generally more secure. Aim for passwords that are at least 12 characters in length or longer.
Avoid Common Words: Avoid using common words, phrases, or patterns in your passwords. Attackers often use dictionary attacks to guess passwords.
Unpredictable Combinations: Create passwords that are not based on easily guessable patterns, such as keyboard patterns or common sequences.
Avoid Personal Information: Don't use easily discoverable personal information, such as your name, birthdate, or family members' names, in your passwords.
Unique Passwords: Use different passwords for different accounts and services. Reusing passwords increases the risk if one account is compromised.
Password Manager: Consider using a password manager to generate, store, and manage complex passwords for different accounts. Password managers can help you maintain strong and unique passwords for each service you use.
Two-Factor Authentication (2FA): Enable 2FA wherever possible. Two-factor authentication adds an extra layer of security by requiring a second form of verification (e.g., a code sent to your phone) in addition to your password.
Regularly Update Passwords: Change your passwords periodically, especially for critical accounts. Avoid using the same password for an extended period.
Stay Informed: Keep up with security best practices and be aware of common password vulnerabilities and attack techniques.

8. What are modules on Linux system? How do you use them? Explain.

In a Linux system, a module, also known as a kernel module or a loadable kernel module, is a piece of code that can be dynamically loaded or unloaded into the running kernel without the need to reboot the system. Kernel modules extend the functionality of the Linux kernel, allowing you to add support for new hardware, filesystems, or functionality without the need to recompile the entire kernel.

Here's an explanation of what modules are and how to use them in Linux:

1. Purpose of Kernel Modules:

Kernel modules serve various purposes, including:
- Adding support for new hardware devices, such as network cards, graphics cards, or storage controllers.
- Extending filesystem support, allowing Linux to read and write to different filesystem formats.
- Implementing additional kernel features or functionality, such as file compression or encryption.
- Supporting third-party or out-of-tree drivers and features.

2. Module Loading and Unloading:

Modules can be loaded (inserted) into the kernel or unloaded (removed) from it using specific commands and utilities.
Common module-related commands include:
- modprobe: Used to load and unload modules and handle module dependencies.
- insmod: Used to insert modules into the kernel.
- rmmod: Used to remove (unload) modules from the kernel.

3. Discovering Available Modules:

You can use commands like lsmod or modprobe -l to list the currently loaded modules or discover available modules on your system.

4. Module Dependencies:

Modules can depend on one another. For example, a module for a specific hardware device may depend on a more generic module for that device class. When you load a module, the system automatically loads its dependencies.

5. Module Configuration:

Module configuration files are typically located in the /etc/modprobe.d/ directory. These files specify module options, blacklisting, or other configuration settings.

6. Module Autoloading:

Linux systems can be configured to autoload modules when a corresponding hardware device is detected. This is often managed through the udev subsystem.

7. Managing Modules with modprobe:

The modprobe command is commonly used to manage modules. It can load and unload modules as well as handle module dependencies.
For example, to load the usb-storage module, you can use:
```
sudo modprobe usb-storage
```
To remove the module:
```
sudo modprobe -r usb-storage
```

8. Module Configuration Files:

Module-specific configuration files may be located in /etc/modprobe.d/ or /lib/modprobe.d/. These files allow you to specify module options or blacklist certain modules.

9. Blacklisting Modules:

You can blacklist modules to prevent them from being automatically loaded. This is useful when you want to use a different module or driver for a specific hardware component.
To blacklist a module, create a configuration file with the module name in /etc/modprobe.d/ and add the line blacklist module_name.

10. Module Utilities: - In addition to the mentioned commands, other utilities like lsmod (list loaded modules), depmod (generate module dependency information), and modinfo (display information about a module) are available for managing and inspecting modules.

11. Kernel Module Development: - Developers can create their own kernel modules to add custom functionality to the Linux kernel. These modules are typically written in C and compiled against the kernel headers of the target system.

Kernel modules are a powerful and flexible way to extend the functionality of the Linux kernel. They are commonly used to support various hardware devices and to add new features or drivers to a running Linux system. When using modules, it's essential to manage them carefully to ensure system stability and compatibility with hardware and software components.

9. Why not use root account all the time? Explain.

Using the root account all the time, especially for routine tasks and general use, is strongly discouraged in Linux for several important reasons:

Security Risk: The root account has unrestricted access to all system resources and commands. Using it for everyday tasks increases the risk of accidentally making system-altering mistakes or executing harmful commands. If a malicious actor gains access to the root account, they can cause significant damage to the system.
Accidental Data Loss: With root privileges, you can modify or delete system files and directories critical for the operating system's functionality. Accidental data loss or system misconfiguration can occur when using root without caution.
Limited Accountability: When using the root account, actions taken are often not logged or attributed to a specific user. This lack of accountability makes it challenging to trace who made changes or mistakes in the system, hindering troubleshooting and security auditing.
Malware and Exploits: Malware or malicious software often targets the root account since compromising it provides full control over the system. By using a non-root account, you reduce the likelihood of your system being compromised by malware.
Best Practices: It is considered a best practice in Linux system administration to use the root account sparingly and only when necessary for administrative tasks that require elevated privileges.
Principle of Least Privilege (PoLP): The PoLP is a security principle that suggests granting users the minimum level of access necessary to perform their tasks. Using a regular user account with limited privileges follows this principle and reduces the attack surface of the system.

Instead of using the root account, Linux encourages the use of the following security practices:

Use of sudo: The sudo (superuser do) command allows authorized users to execute specific commands with elevated privileges without logging in as the root user. It provides a way to perform administrative tasks safely while maintaining a separation between regular user privileges and administrative privileges.
Limited Use of su: The su (switch user) command can be used to temporarily become the root user or switch to another user account. However, it should be used judiciously and only when necessary for administrative tasks.
Regular User Accounts: Users should have their own regular user accounts for day-to-day activities. These accounts have limited access and are less likely to cause unintentional system changes or damage.
Password Policies: Enforce strong password policies for user accounts, including regular password updates and the use of complex passwords. Consider implementing two-factor authentication (2FA) for added security.
User Groups: Assign users to appropriate user groups to control access to specific resources and commands. Grant access only to users who need it.
Audit and Monitoring: Enable system logging and monitoring to track user actions and system events. This helps identify and respond to security incidents or unauthorized activities.

10. Explain the symbolic and absolute method for giving permission to a file. Change the permission of a file named GPT.sh

(1) write only by owner (2) read and execute by other (3) Execute by all (4)read by owner, write by group, read by others

In Linux, file permissions can be set using both symbolic notation and absolute notation (also known as octal notation). Let's first explain the symbolic method and then the absolute method for changing the permissions of a file named GPT.sh according to the specified criteria:

Symbolic Method:

In symbolic notation, you can use the chmod command to change file permissions based on the following symbols:

u: Owner (user)
g: Group
o: Others (everyone else)
a: All (u + g + o)
+: Add permission
-: Remove permission
=: Set permission explicitly

Permissions:

r: Read
w: Write
x: Execute

To change the permissions of GPT.sh as specified:

# (1) write only by owner
chmod u+w GPT.sh

# (2) read and execute by other
chmod o+rx GPT.sh

# (3) Execute by all
chmod a+x GPT.sh

# (4) read by owner
chmod u+r GPT.sh

# (5) write by group
chmod g+w GPT.sh

# (6) read by others
chmod o+r GPT.sh

Absolute Method (Octal Notation):

In absolute notation (octal notation), each permission is represented by a three-digit number (base 8) where each digit corresponds to a user category (owner, group, others). The values for each permission are as follows:

4: Read permission
2: Write permission
1: Execute permission
0: No permission

To set permissions in octal notation, you calculate the sum of the values for the desired permissions and then assign that value to the file.

To achieve the same permissions as specified:

# (1) write only by owner (u=2, g=0, o=0)
chmod 200 GPT.sh

# (2) read and execute by other (u=0, g=0, o=5)
chmod 005 GPT.sh

# (3) Execute by all (u=0, g=0, o=1)
chmod 011 GPT.sh

# (4) read by owner (u=4, g=0, o=0)
chmod 400 GPT.sh

# (5) write by group (u=0, g=2, o=0)
chmod 020 GPT.sh

# (6) read by others (u=0, g=0, o=4)
chmod 004 GPT.sh

1. What is SUDO? Describe the root account with the procedure to login as root user?​

2.What are roles and responsibilities of a Linux administrator in Linux system?​

3.What is a root user? Explain the methods to monitor system performance in Linux Environment with example.​

4.What is Kudzu? What are the module configurations commands? Explain with example of each.​

5. What is root account and root directory? How can you switch user in Linux from terminal? Also explain the importance of sudo command.​

6. What is role of super user in linux?​

7. What do you mean by shadow password file? Explain how you can make your password more secure and stronger?​

8. What are modules on Linux system? How do you use them? Explain.​

9. Why not use root account all the time? Explain.​

10. Explain the symbolic and absolute method for giving permission to a file. Change the permission of a file named GPT.sh​

1. What is SUDO? Describe the root account with the procedure to login as root user?