DEV Community: Calzy

Question and Answer

Calzy — Thu, 13 Apr 2023 14:36:42 +0000

Mutual Exclusion

Definition
A mutual exclusion (mutex) is a software object that stops several users from accessing a shared resource at the same time.

How to handle

Use Token based algorithm, where a unique token is shared among all the sites.

Non-token based approach, where a site communicates with other sites in order to determine which sites should execute critical section next.

Quorum based approach. Instead of requesting permission to execute the critical section from all other sites, each site requests only a subset of sites which is called a quorum.

Deadlock

Definition
A deadlock occurs when a collection of processes is stalled because one process is holding a resource and waiting for another resource to be acquired by another process.

How to handle

Prevention, prevent it from happening.

Avoidance, use resource allocation algorithms.

Detection and Recovery, examine the state of the system to identify if a deadlock has occurred.

Timeouts, ensure that a process does not remain blocked indefinitely.

Starvation

Definition
Starvation is an issue that happens when high priority processes continue to run while low priority processes are halted indefinitely.

How to handle

A freelancing manager should be in charge of CPU resource allocation to guarantee that resources are distributed evenly.

Starvation can develop as a result of random process technique selection.

To minimize famine, process aging criteria should be considered while allocating resources.

To deal with famine, a scheduling method with a priority queue might be utilized.

Data Coherence

Definition
Data coherence encompasses both uniformity across shared resource data and logical links and completeness inside and between data sets.

How to handle

Cache coherence protocols are used to ensure that all processors have the same value of a shared variable by maintaining consistency between cached copies of the variable across all processors.

Memory barriers or synchronization instructions are used to ensure that changes made to a shared variable are visible to all processors by flushing any cached values and updating main memory.

Locking or semaphores can be used to ensure that only one thread can modify a shared variable at a time, preventing race conditions and ensuring consistency.

Concurrency

Calzy — Thu, 13 Apr 2023 14:17:50 +0000

Concurrency is the simultaneous execution of several instruction sequences. It occurs in the operating system when many process threads are executing concurrently. Threads of running processes constantly communicate with one another via shared memory or message forwarding. Through this article, I am going to discuss several key points about concurrency.

One of the most common problem occurring in concurrency is the producer-consumer problem. Before we can understand the Producer-Consumer Problem, we must first define the terms Producer and Consumer.

In an operating system, a Producer is a process that may generate data or items.
The Consumer is a Process that can consume the data/item created by the Producer.
A memory buffer is shared by both the Producer and the Consumer. This buffer is a certain size of memory in the system that is utilized for storing. The producer produces the data into the buffer and the consumer consumes the data from the buffer.

Source: Scaler

The Producer-Consumer dilemma is a well-known synchronization issue in computer systems. The problem is as follows: there is a fixed-size buffer, as well as a Producer and a Consumer process. The Producer operation generates an item and inserts it into the shared buffer. The Consumer process "consumes" objects that are in the shared buffer.

Other concept of concurrency is Mutual Exclusion. Mutex, or mutual exclusion, is a unit of code that prevents concurrent access to shared resources. Mutual exclusion is a concurrency control characteristic that is implemented to avoid race problems. In plain terms, it is a condition in which a thread of execution is never involved in a crucial part at the same time as another thread of execution that is also utilizing the critical section. This crucial part can be characterized as a time when the thread of execution accesses a shared resource, such as a data object, which several concurrent threads may seek to change.

Another concurrency concept is Semaphores. Semaphores are synchronization mechanisms that are used in computer systems to synchronize the activity of various processes. They are used to ensure mutual exclusion, avoid race situations, and establish process synchronization.

There is also Starvation concept in concurrency. Starvation is an issue that happens when high priority processes continue to run while low priority processes are halted indefinitely. A continual stream of higher-priority processes in a densely loaded computer system can prevent a low-priority operation from ever receiving the CPU. In times of scarcity, high priority activities consume all available resources. Aging can help alleviate the problem of famine. The priority of long waiting processes is steadily elevated as people age.

Concurrency is governed by a number of principles. Some of the key concepts and approaches connected to concurrency are the producer-consumer issue, mutual exclusion, semaphore, and starvation.

Processes and Threads

Calzy — Thu, 16 Mar 2023 17:59:23 +0000

Calzy Akmal-2101569

Process Management is a series of activities performed by a computer system to manage, control, and optimize the performance of processes running within the system. Stallings and Tanenbaum (2020) state that process management in an operating system requires proper strategies in resource allocation and memory management to ensure efficient system operation. Process management encompasses several tasks, such as creating and terminating processes, scheduling and allocating computer resources like the CPU, memory, and I/O devices, inter-process communication, and activity synchronization, memory management, and process supervision to prevent system conflicts and failures.

In creating a program using a high-level programming language, a translation process is needed as the computer operates using binary systems consisting of two numbers, 0 and 1. Hence, a compiler is used to translate the high-level language into binary language that can be processed by the computer so that the program written by humans can be understood and executed by the computer.
The role of process management is to optimize the set of code that has been translated by the compiler to make the memory needed by the computer to run the program more orderly and efficient. Additionally, process management also allocates computer resources required to run the program while supervising any execution failures.

The allocation process is performed by the operating system, which automatically divides the necessary memory to run the program so that the program can run optimally and minimize any issues that may arise. The operating system executes the executable created by the compiler by inserting the program's data into memory and allocating the resources needed to run the program.

When the program is running, the status changes from being just a program to a process. According to Tanenbaum and Bos (2015), a process is a program being executed by the operating system, including the data related to the execution such as memory addresses, status, and resource management. In the past, computers could only run one program being executed as the machine's capability was insufficient to run a multi-process system. With technological advancements, computers can now run multiple processes simultaneously, with optimized memory and better performance.

Within a process, there are "threads" that function as the basic execution unit in a program or process. According to Silberschatz, Galvin, and Gagne (2013), a thread can be thought of as a sub-component of a process that can be independently scheduled by the operating system. Threads improve system efficiency and responsiveness by allowing multiple tasks to be executed in parallel within a process. In this regard, threads allow the operating system to effectively utilize processing power.

Process management is crucial in ensuring the efficient execution of multiple processes and threads in an operating system. It involves the allocation of resources, scheduling, memory management, and process communication. A significant challenge in process management is avoiding conflicts among processes, particularly in cases where multiple processes are competing for the same resources.

Operating System Exercise

1. Managing Service

SSHD

SSHD Stop

SSHD Start

SSHD Restart

2. Running Init

SSH Status

3. TOP

References:

Silberschatz, A., Galvin, P. B., & Gagne, G. (2013). Operating
system concepts (9th ed.). John Wiley & Sons.
Stallings, W., & Tanenbaum, A. S. (2020). Operating Systems:
Internals and Design Principles. Pearson.
Tanenbaum, A. S., & Bos, H. (2015). Modern operating systems (4th
ed.). Pearson Education.

File Management

Calzy — Tue, 28 Feb 2023 18:28:57 +0000

Why do we need File Management?

Research suggests that proper file management is crucial for organizing, storing, and accessing digital information efficiently and effectively, which is essential for effective work and productivity [2].

Effective file management can lead to optimized storage space utilization, as well as the regular backup and easy recovery of important files in the event of damage or loss. There are some key factors about the importance of file management, such as:

File Organization
By organizing digital files into a structured and logical form, proper file management allows for a quicker access and make it easier to locate files.

Space Management
Effective file management allows for more efficient storage management on the computer or other devices by regularly deleting unnecessary files, which is particularly scathing when working with limited storage capacity.

File Recovery
Through the implementation of proper file management, important files are regularly backed up so that they are easily recoverable in the event of data loss, damage, or corruption.

Collaboration
Effective file management allows for easy and secure sharing and collaboration of files with others, without compromising the security or integrity of the files.

Security
Proper file management allows robust security protocols to safeguard sensitive information and restrict access to important files to authorized personnel only. This protects valuable data from unauthorized access and also mitigates the risks of data breaches or cyberattacks.

As pointed out by [1], proper file management is important for organizing and securing digital files, optimizing storage space, and ensuring efficient and secure collaboration with others. In conclusion, effective file management can reduce the time needed on working with files, enhance productivity.

Comparison Between FAT and NTFS

Tree-Structured Directory

As the name implies, a Tree-Structured Directory is a type of file organization system in which files are structured in a tree-like structure. Inside this system, the root directory is located at the top of the hierarchy, and all other directories and files are arranged beneath it in a hierarchical structure. Each directory can contain multiple subdirectories, and each subdirectory can contain additional files and directories [4].

Geeks for geeks

Acyclic-Graph Directory

Also known as Directed Acyclic Graph (DAG) directory, is a file organization model that represents the relationship between each file in a graph form structure that is interconnected. According to [4], in a DAG directory, each file or directory is represented as a node in the graph, and each link between nodes represents a relationship between files or directories. This model is different to the Tree-Structured Directory in which a DAG can have multiple parent directories, where the Tree-Structured Directory can only have one.

Binary Terms

Exercise Practice Module

Making a directory

Creating an empty file

Writing a file

Instant write onto a file

Read file

Delete file

Locate file location

Truncate file

Directory list

Copy and cut file

Recursion

Change access

Changing owner

References

[1] Deepika, C., & Mukesh, K. (2016). Managing Digital Information: The Need for Effective File Management. International Journal of Science and Research (IJSR), 5(7), 2602-2605.
[2] Hussain, M., Fiaz, M., Ashraf, S., & Raza, S. (2017). A
Comparative Study of File Management Techniques. Journal of
Information Engineering and Applications, 7(2), 51-59.
[3] Johnson, R. E., & Hartmanis, J. (1990). A taxonomy of computer
systems and their storage hierarchies. ACM Computing Surveys
(CSUR), 22(4), 283-341.
[4] Satyanarayanan, M., Kistler, J. J., Mummert, L., Pillai, P., & Rosenblum, M. (1990). Integrated file and memory management in a client-server environment. ACM Transactions on Computer Systems (TOCS), 8(3), 238-265.
[5] Silberschatz, A., Galvin, P. B., & Gagne, G. (2018). Operating system concepts (10th ed.). Wiley.
[6] Zhang, J., & Qi, L. (2006). A new dynamic disk allocation
algorithm based on LVM2. In Proceedings of the 2006
International Conference on Computational Intelligence and
Security (pp. 121-125). IEEE.

How To Install Ubuntu Server on Virtual Machine

Calzy — Wed, 15 Feb 2023 07:14:28 +0000

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First, open up the link down below and select the button to download the Ubuntu Server.iso on your computer.

If you have finished downloading, I assume you have already installed the Virtual Box (if you haven't, open this link to see on how to install the Virtual Box: https://dev.to/calzkmal/how-to-install-ubuntu-os-on-virtual-machine-364i).

Now open up the Virtual Box to proceed to the next step.

Click the 'New' button to create a new Virtual Machine (VM) on your desktop.

Fill up the required field to complete the initial setup. Give your VM a name, select where do you want to put the VM on your desktop, and select where the .iso is located. After that, press next to proceed.

Fill out the 'Username' and 'Password' columns according to your own preferences, and change the 'Hostname' and 'Domain name' columns if you wanted to. After that, press next to proceed.

After that, allocate the memory needed for the machine to work on your desktop. Recommended amount for the 'Base Memory' is around 8192 MB, and 4 CPU for the 'Processors'.

Lastly, allocate the storage amount for the server to operate on the VM. Around 25 GB of storage is enough for the machine to work.

There you go! If you have finished all the steps required on the VM installation, the last thing to do is to see all the summaries of the settings that you have set before. Press the 'Finish' button if you feel good enough about the settings.

Congratulations! You have succesfully installed the Ubuntu Server on your VM. Now, fire it up to use it.

How To Install Ubuntu OS on Virtual Machine

Calzy — Sat, 11 Feb 2023 09:49:40 +0000

cout << "Calzy Akmal - 2101569";

Virtual Machine Installation

First of all, make sure you have already installed the Virtual Machine on your desktop. If you haven't already, copy the link down below and paste it into your browser to download the Oracle VM VirtualBox installer.

https://www.virtualbox.org/wiki/Downloads

Select the best version that suited your desktop the most. In this case, I choose the "Windows hosts" because my desktop is running on Windows.

After that, open up the installer and proceed through the steps required.

If you have finished installing the Virtual Machine on your desktop, now open up the link down below and download the Ubuntu OS to proceed to the next steps.

https://ubuntu.com/download/desktop

After you have finished downloading the Ubuntu OS, proceed to fire up the Virtual Machine that has been installed before.

Proceed To Install Ubuntu

Now, press the "New" button on the UI and fill out the field required.

Name: If you include the word Ubuntu in your name the Type and Version will auto-update.
Machine Folder: This is where your virtual machines will be stored so you can resume working on them whenever you like.
ISO Image: Here you need to add a link to the ISO you downloaded from the Ubuntu website.

Skip the Unattended Installation checkbox because we want to install Ubuntu unattendedly.

Create A User Profile

The default credentials are:

Username: vboxuser
Password: changeme

Change it as preferred.

Define The Virtual Machine's Memory Allocation

In this section, we can customize the resources that our Virtual Machine's memory and processors will use from our device. It is recommended to allocate the VM with around 8 GB of RAM (Although that 4 GB is still fine) and 4 CPUs. Try to keep the sliders remain in the green area to prevent issues with the machine.

Then, we need to allocate the amount of storage for the hard disc of the Virtual Machine. The recommended size is 25 GB for Ubuntu. If you want the machine to pre-allocate full amount, check the "Pre-allocate Full Size" check box.

Click next to see the summary of the settings that are applied for the installation.

After that, hit finish to complete the installation.

Firing Up The Ubuntu OS

Now, open up the OS and hit the "Start" button to initiate the OS

After some while, the OS will finally be opened up and there will be some installation verifying done by the system. Just wait it out and don't press anything until it finished.

Once the installation finished, the machine will automatically restarts to finish up everything and you are ready to use the Ubuntu OS.