#binary semaphore

[digitalthinkerhelp]

Binary Semaphores in Operating System with Examples

From this article, we will guide you all possible stuffs about what is binary semaphore in OS along with their examples; as well as advantages and disadvantages with ease. After reading this article, you will be getting fully educated about Binary Semaphores in Operating System without any hindrance.

Binary Semaphores Tutorial Headlines:

In this section, we will show you all headlines about this entire article; you can check them as your choice; below shown all:

What is Binary Semaphore in OS?

Working Structure of Binary Semaphore

Uses of Binary Semaphores

Key Features of Binary Semaphore

Binary Semaphore Example with Implementation in C

Advantages of Binary Semaphores

Disadvantages of Binary Semaphores

FAQs (Frequently Asked Questions)

What is the purpose of using a binary semaphore?

How does a binary semaphore support synchronization in a multi-threaded environment?

Can binary semaphore be used for inter-process synchronization?

Can binary semaphore be used for inter-process synchronization?

Let’s Get Started!!

[thecrazyworldbuilder]

Another reminder that there's no universal symbolism.

And, by proxy, a reminder that languages are a way of communicating one information via different methods. Sign language uses hand gestures and movements, verbal languages take speech, there's several real-life whistling languages, there's the Morse code, there's binary and all sorts of numeral systems, there's the semaphore, ciphers like the "dancing men" or pigpen, there's the heraldics of Europe, there's the language of flower bouquets and even secret calligraphy languages that hide second layer meanings in the way the letters of a word are written down to the amount of decorative loops and tilt.

Language is a magical thing in a way that anything can be considered language, once there's a system of decoding it. Language could be a ruler with each mark assigned to a letter, used for measuring specific sticks the length of which encode the meaning of the message.

There's so many possibilities. I'm going crazy over them.

[lopez-richter-fangirl]

Can you post what you think the answers to the post cards are for those of us who are too dumb to figure it out

First, I knew the answers anyway because the locations were already shared on the patreon, but it’s still fun to solve puzzles lmao. Second, I know some people weren’t sure about this step so you can go to the website https://www.tincanbros.com/find-tinlightenment? to confirm the locations when you solve the codes (but you don’t necessarily need to!). The codes used are binary, semaphore, dancing man, pigpen, and morse (there’s an error in their morse code!) in that order. Corey said in discord, google is your friend!!

[awigglycultist]

Tin can bros ciphers, here's what I got so far (other ppl have figured it out quicker than me but idc this is the first time I'm really able to work on the puzzles starkid and tcb have done):

Ok can't actually type in any of the codes from here so here's just what cipher they are and what they equal

1.) 10101111110101100, it's binary code, = - Ö

Edit: ok this isn't right, there's something going on where whatever it actually is isn't showing up properly in binary translators

2.) flag semaphore = EH ONE

3.) dancing men cipher = E C THREE N

4.) pigpen cipher = five thousand

[the-typing-dragon]

Are you more of a telegraph nerd or a semaphore enjoyer?

Definitely telegraph. I like my tech and i like my binary encoding methods

[mdraihanurrahmanrocky]

Telegraph Data: The Evolution of Instant Communication and Its Modern Legacy

In the modern world, where data flows across continents in milliseconds, it’s easy to forget the humble origins of global communication. The phrase “telegraph data” may evoke images of Morse code and clacking machines, but it represents a pivotal milestone in the history of information technology. Telegraph data laid the foundation for our current digital age. Understanding what telegraph data is, how it evolved, and what role it plays today helps us appreciate the journey of global communication from wires to wireless.

What is Telegraph Data?

Telegraph data refers to the information transmitted via a telegraph system—a communication method that dates back to the early 19th century. Telegraph systems work by converting text-based messages into coded electrical signals (most famously Morse code), which are then sent through wires to a receiving station where they are decoded.

In its simplest form, telegraph data includes:

Textual messages (encoded using Morse code or similar)

Transmission metadata (time sent, sender and receiver information)

Operational signals (acknowledgments, errors, and control instructions)

This format of communication was revolutionary at the time, transforming the pace and scope of information exchange.

The Birth of the Telegraph System

The invention of the electrical telegraph is credited to several inventors, with Samuel Morse and Alfred Vail being the most notable for developing the Morse code in the 1830s and 1840s. The first successful demonstration took place in 1844 between Washington, D.C., and Baltimore, with the famous message.

Prior to the telegraph, long-distance communication relied on physical means—letters, messengers, and semaphore signals—which were time-consuming and unreliable. The telegraph reduced transmission times from days or weeks to mere minutes, introducing a new era of rapid communication.

How Telegraph Data Changed the World

The impact of telegraph data was immense, reshaping multiple facets of society:

1. Military Communication

Telegraph systems allowed military commanders to send orders and receive updates in near real-time. During the American Civil War, the Union army's telegraph data  effective use of the telegraph gave it a strategic advantage.

2. Economic and Financial Markets

Telegraphy transformed business and finance by enabling stock prices, commodity prices, and transaction orders to be sent instantly between cities and countries. The telegraph was the first step toward the real-time global financial systems we have today.

3. Journalism and News Distribution

The rise of wire services like Reuters and the Associated Press was made possible by telegraph data. These services could now gather and disseminate news across the globe rapidly, revolutionizing the media industry.

4. Social and Personal Communication

For the first time, individuals could send personal messages to distant friends and family members, albeit at a cost. The telegram became a popular means of communication for urgent or significant news.

Technical Aspects of Telegraph Data

Though simple by today’s standards, telegraph data had several technical characteristics that made it effective:

Binary Encoding: Morse code is essentially a binary system of "dots" and "dashes" (short and long signals), much like the 0s and 1s used in modern digital systems.

Time Synchronization: Telegraph networks needed time-coordinated transmissions and receipts to avoid confusion.

Data Compression: Morse code was an early form of data compression, with shorter signals for more frequently used letters (e.g., “E” and “T”).

Error Handling: Telegraph operators developed methods for confirming receipt and requesting retransmission in case of errors—precursors to modern error-checking protocols.

Telegraph Data and the Advent of Submarine Cables

One of the greatest engineering feats of the 19th century was the laying of transoceanic telegraph cables. The first successful transatlantic telegraph cable, completed in 1866, connected North America and Europe, enabling near-instantaneous communication across the ocean.

These cables carried telegraph data at speeds unimaginable just a few decades prior and laid the groundwork for the global communication networks we rely on today.

Transition from Telegraph to Modern Data Transmission

While the telegraph dominated communication for nearly a century, it eventually gave way to newer technologies:

Telephone (1876): Enabled voice communication, replacing text-based telegrams for personal and business use.

Radio (1890s–1920s): Wireless telegraphy enabled communication without physical wires, essential for ships and remote locations.

Digital Computing and the Internet (20th century): Expanded the scope and capacity of data transmission far beyond the constraints of Morse code.

Interestingly, the foundational principles of telegraph data—encoding, transmission, synchronization, and decoding—still underpin modern data communication, albeit in vastly more complex and efficient forms.

Telegraph Data in Modern Context

Although traditional telegraph services have largely been phased out (the last telegram in the U.S. was sent in 2006), telegraph data is still studied and applied in niche contexts:

1. Data Communication Protocols

Modern digital communication protocols like TCP/IP echo many of the error correction and flow control methods originally developed for telegraphy.

2. Cybersecurity

The concept of encoding and decoding messages securely has its roots in telegraph communication, and the vulnerabilities of early systems still inform modern encryption methods.

3. Historical Data Mining

Historians and data scientists are analyzing historical telegraph records to understand social patterns, economic trends, and political decision-making in the 19th and 20th centuries.

4. Ham Radio and Morse Code

Amateur radio operators still use Morse code today, especially in emergencies where voice or digital communication fails.

The Legacy of Telegraph Data

The influence of telegraph data goes far beyond its original application. It was the first instance of separating the message from its physical medium—something foundational to digital communication. The idea that information could be encoded, transmitted, stored, and decoded independently of its content paved the way for everything from emails to satellite data.

Key legacies include:

Standardization of Time Zones (for synchronized communication)

Establishment of Global Communication Infrastructure

Conceptual Foundations for the Internet and Cloud Computing

Challenges Faced by Telegraph Systems

Despite its revolutionary nature, telegraphy had limitations:

Speed: Messages were encoded and decoded manually, limiting throughput.

Cost: Sending a telegram was expensive, especially over long distances.

Security: Early systems were vulnerable to interception and tampering.

Training: Operators needed skill and precision to send and receive messages accurately.

Many of these challenges echo in modern systems, though addressed with far more sophisticated tools and automation.

Future of Telegraph-Inspired Technologies

Telegraph data as a physical medium may be obsolete, but its principles are thriving in future technologies:

Quantum Communication: Echoes the idea of encoding and transmitting data through secure channels.

Internet of Things (IoT): Devices constantly send small packets of data—much like telegraph systems once did.

Neural Interfaces: The brain’s electrical signals are, in many ways, similar to Morse-coded impulses sent down a wire.

In educational and military contexts, telegraph data principles are still taught to explain the basics of digital transmission and network theory.

Thanks for reading..

SEO Expate Bangladesh Ltd.

[ankitcodinghub]

CSC718 Parallel Programming Midterm Solved

Total: 100 points (Midterm is a take-home exam. It includes four questions. The last one is a programming assignment. Please submit all your solutions and source code through D2L midterm Dropbox.) 1) (20 points) Binary semaphores only allow the integer to hold the values 0 and 1. However, binary semaphore are easier to implement than general semaphores. Here we demonstrate that a general…

[codingprolab]

CMSC 312 Assignment #2

1) Implement the counting semaphores using binary semaphores. Pseudo-code for the implementation is given in the attached notes on BB: 10xcountingSemUsingBinarySem.pdf Use the bounded-buffer producer-consumer problem as uploaded on BB (first code at https://jlmedina123.wordpress.com/2014/04/08/255/). Show the output of this code for BOTH the incorrect and correct implementations. Also, attach…

[vivisols]

Are you good at decoding messages? Not just the simple binary or Morse, but lesser known codes like Base64 or rot13?

if someone sent you something coded in Base64 would you recognize it or just see as gibberish and delete it?

would you use coded messages in your work? Hide secrets in plain sight? Are you one for that kind of sneakiness?

do you like mystery in that way? Or do you prefer to be blunt about your works? Your mystery not hidden by a string of mixed up letters? Or perhaps like no mystery at all?

also, would you just go the easy way and pull up a translator, or try to decode on your own? (I personally do both, depending on if I’m up to it or not, decoding is tedious)

im good at decoding messages with binary, morse code, and even semaphore! i can do rot13 pretty easily most of the time too, although I SUCK with everything else xD and id probably just see it as gibberish since unless it made sense in the context of something recent or specified that it was code. im not the best at recognizing things as code if they just randomly pop up and aren't specified as such xDDDD

i definitely am! :3 i love hiding coded messages in my works!!!!! and there are definitely a LOT of secrets hidden in plain sight in my writing, symbolism my very much BELOVED!!!!!!!!! i haven't really had a chance to properly take a crack at actual code within my works but!!!! id love to eventually!!

i typically LOVE those sorts of mysteries!!!! although the coded sections have to be properly dosed for me to actually enjoy it xP stuff like binary and morse code have to be used sparingly and with PURPOSE that makes sense in the context of the story, otherwise i find it more trouble than its worth tbh. as fun as it is to use and decode, it gets tiring after a while, especially if its not used to conceal anything really interesting! xP

when i write, i love including a whole bunch of secrets that you can find if you really dig! though they usually aren't hidden by any sort of code, they just rely on symbolism and prior knowledge of certain symbols! mystery and symbolism my VERY much beloved!!!

i typically try to decode on my own, but if its a LOT to decode or something i dont know too well then im bringing out the translator xD

[hatchetfieldtheories]

The clocks look to be semaphore considering the flags on the stamp, however I don't know what its supposed to mean once translated.

Ive got everything other than the morse code (in theory, 2 of them dont make much sense to me rn including the dancing man one) - the only one really that makes sense to me is the binary one 🤣

Stickmen are my new hexagons

[theficpusher]

Insomnis by FullOnLarrie | G | 500 Harry’s been having trouble sleeping. Louis makes everything better.

Taught Me How to Be Someone by threeturn | T | 1093 “Don’t fuck the robot,” says Louis. “Please Harry, don’t try to fuck the robot.”

(while you count clouds) by softly (alexenglish) | G | 1628 When you’re around I don’t know how to hide my feelings. I count in binary, in my head. zero one one zero one one and you count clouds.

when you feel the most alone by merryofsoul | T | 1842 Louis is an android -- who has feelings thank you very much -- and Liam doesn't have the time.

Soul by roaroftheninth | T | 4772 Liam tosses a grin back over his shoulder. “What are you going to do when I’ve gone and there’s no one around to drive you round the bend?” Louis’ bike coasts to a stop. It happens so slowly that by the time he’s at a standstill, Liam is far ahead, up by the curve. “I’ll forget.” Liam stops much more quickly. They’re alone in the dome; their private conversation can be held across thirty feet of open space. “You’ll what?” Louis watches him. “I’ll forget,” he repeats. “Not the way you forget things, when you can’t pinpoint them but you still carry them in your heart. I’ll just have my hard drive wiped.” Or: Louis is the medical android tasked with taking care of Liam in a world after nuclear war.

kettle and mirror by yasgorl | E | 5228 The delivery truck made it halfway up the long, rutted road, quickly turning white in the evening snow flurry, before leaving its burden at the turn into Liam’s driveway. Or, the one where Zayn is a robot.

Tubes And Wires And Careful Notes by zzegnas | T | 5306 “Zayn, you are displaying a slightly elevated percentage level of hostility. Your stress and anxiety levels are competing with each other as well. I believe your new position as head stock boy is a contributing factor.” “Thanks, but I didn’t need the physical.” “You seem exasperated,” Harry points out. “Would you like to hear a joke?” — Zayn notices a glitch in Harry's programming. Niall pretends it doesn't exist.

Semaphore Out On The Floor by zzegnas | T | 5869 “My programming detects you were telling a joke. I am amused.” “Good!” Niall chuckles, patting Harry on the shoulder. “At least you a sense of humor.” “In lieu of your humor, I have just downloaded ‘The World’s Greatest Dad Jokes’ into my library for future reference. Fairly impressive and entertaining, would you like to hear one?” — Due to recent memory problems, Niall is given a service android programmed to be his companion, who proves to be both a help and an unintentional nuisance.

[asktheraggededges]

So in Nada's hobbies, has she ever tried something creative? Like drawing or writing?

She wrote a VERY impressive and interesting play once, actually!

It took me a while to read through, because the parts of it that weren’t written in Nadanese were written in other languages including morse code, binary, Lacustrian and ...what was this one..?

Hexidecimal.

Presumably because the play was meant to be interpreted through these languages also.

Honestly, it was really really good. Sort of autobiographical if I’m reading it right. But I don’t really see it seeing the light of day, sadly. Four main reasons.

1. The biggest one is the language barrier and the amount of interpretation required. Not everyone is going to know semaphore or what certain dance moves mean, and some of the scenes where that is used is integral to the plot.

2. Budget. I love the scene with the giant talking cat that keeps on being eaten then growing back stronger, but I don’t wanna think about how we would broach that special effect.

3. It is long. Like, really long. Even if we took out the (honestly fairly important) stretches of silence, the play would still be about 16 hours long.

4. There is a LOT of graphic sexual content in this script. it’s not actually gratuitous - it generally represents something but man, we would need all sort of clearances and contracts for this. There are like, five prolonged sex scenes in this play.

It killed me to break all this to Nada, because she’s actually pretty good but she seemed okay with it. I think she knew it was never gonna happen and just enjoyed the exercise.

She’s neat. kinda wish she didn’t make feel like I was travel sick.

[billconrad]

Roman Numerals

    Education did not come easily for me, especially at the beginning. Right when I mainly had grasped basic arithmetic, the teacher introduced something radical, Roman Numerals. What are they? A long time ago, before numerical symbols like 1, 2, 3, 4, 5 were invented, the Romans developed an unorthodox method. For example, three capital I’s represented the number 3, III. Unfortunately, numbers quickly became confusing. Four was IV, five was V, and six was VI. Addition and subtraction are required to count? Lame!

    My six-year-old brain hurt when the teacher explained Roman Numerals, and I could not determine why we were not using what we already knew 4, 5, 6. The answer is that Roman Numerals are the classic method and uplift a document. Umm, alright. Not a great sell.

    Today, we have many ways to represent numbers, including binary (computer gobblygook), hex (more computer gobblygook), text (twenty-six), floating point (complex computer gobblygook), fractions, morse code, color code (electrical engineering gobblygook), maritime flag and even imaginary (complex math gobblygook). Did you get the joke? Imaginary numbers are complex. Hahaha. Alright, too much math.

    Why am I discussing this topic? It is time to retire Roman Numerals because they are no longer helpful, which would be one less thing to cram into our overloaded brains. Do they have a legitimate use? I would argue that Roman Numerals, Egyptian pictographs, Inca rope knot language, smoke signals, and semaphores (railroad flags) have no use because we have developed better methods. Plus, we have thoroughly recorded Roman Numerals history and structure for posterity.

    Many carryovers in the English language should also be eliminated, including alternate spellings, disused words, double spaces after the period, double-spaced paragraphs, and old English fonts (fonts that are difficult to read). Plus, there are keyboard keys that never get used, print screen, scroll lock, pause, and insert.

    Yeah, I’m dreaming. Roman Numerals will be used daily until our sun becomes warm to the touch. Why? Umm, tradition? That is not a sound reason, but we love traditions. Or perhaps I am an agelast? (A person who never laughs.) (Another word that we should eliminate.)

  You’re the best -Bill

  May 10, 2023

  Hey book lovers, I published three. Please check them out!

  Interviewing Immortality is a psychological thriller about a 500-year-old woman who forces a disgraced author to interview her.

  Pushed to the Edge of Survival is a drama, romance, and science fiction story about two unlikely people surviving a shipwreck and living with the consequences.

  Cable Ties is a classic spy novel about two hunters discovering that government communications are being recorded and the ensuing FBI investigation.

  These books are available in soft-cover on Amazon and eBook format everywhere.

[computingpostcom]

In this guide, we will install Semaphore Ansible Web UI on CentOS 7|CentOS 8. Semaphore is an open source web-based solution that makes Ansible easy to use for IT teams of all kinds. It gives you a Web interface from where you can launch and manage Ansible Tasks. Install Semaphore Ansible Web UI on CentOS 7|CentOS 8 Semaphore depends on the following tools: MySQL >= 5.6.4/MariaDB >= 5.3 ansible git >= 2.x We will start the installation by ensuring these dependencies are installed on your CentOS 7|CentOS 8 server. So follow steps in the next sections to ensure all is set. Before any installation we recommend you perform an update on the OS layer: sudo yum -y update A reboot is also essential once the upgrade is made: sudo reboot -f Step 1: Install MariaDB Database Server We have a comprehensive guide on installation of MariaDB on CentOS 7|CentOS 8. Run the commands below to install the latest stable release of MariaDB database server. curl -LsS -O https://downloads.mariadb.com/MariaDB/mariadb_repo_setup sudo bash mariadb_repo_setup sudo yum install MariaDB-server MariaDB-client MariaDB-backup Start and enable mariadb database service: sudo systemctl enable --now mariadb Secure database server after installation: $ sudo mariadb-secure-installation Switch to unix_socket authentication [Y/n] n Change the root password? [Y/n] y Remove anonymous users? [Y/n] y Disallow root login remotely? [Y/n] y Remove test database and access to it? [Y/n] y Reload privilege tables now? [Y/n] y Step 2: Install git 2.x on CentOS 7|CentOS 8 Install git 2.x on your CentOS 7 server using our guide below. Install latest version of Git ( Git 2.x ) on CentOS 7 Confirm git version. $ git --version git version 2.34.1 Step 3: Install Ansible on CentOS 7|CentOS 8 Install Ansible on your CentOS 7 server. sudo yum -y install epel-release sudo yum -y install ansible Test if ansible command is available. $ ansible --version ansible 2.9.27 config file = /etc/ansible/ansible.cfg configured module search path = [u'/root/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules'] ansible python module location = /usr/lib/python2.7/site-packages/ansible executable location = /usr/bin/ansible python version = 2.7.5 (default, Nov 16 2020, 22:23:17) [GCC 4.8.5 20150623 (Red Hat 4.8.5-44)] Step 4: Download Semaphore Visit the Semaphore Releases page and copy the download link for your OS. sudo yum -y install wget curl VER=$(curl -s https://api.github.com/repos/ansible-semaphore/semaphore/releases/latest|grep tag_name | cut -d '"' -f 4|sed 's/v//g') wget https://github.com/ansible-semaphore/semaphore/releases/download/v$VER/semaphore_$VER_linux_amd64.rpm Install Semaphore package: $ sudo rpm -Uvh semaphore_$VER_linux_amd64.rpm Preparing… ################################# [100%] Updating / installing… 1:semaphore-0:2.8.53-1 ################################# [100%] Check if you have semaphore binary in your $PATH. $ which semaphore /usr/bin/semaphore $ semaphore version v2.8.53 Usage help document: $ semaphore --help Ansible Semaphore is a beautiful web UI for Ansible. Source code is available at https://github.com/ansible-semaphore/semaphore. Complete documentation is available at https://ansible-semaphore.com. Usage: semaphore [flags] semaphore [command] Available Commands: completion generate the autocompletion script for the specified shell help Help about any command migrate Execute migrations server Run in server mode setup Perform interactive setup upgrade Upgrade to latest stable version user Manage users version Print the version of Semaphore Flags: --config string Configuration file path -h, --help help for semaphore Use "semaphore [command] --help" for more information about a command. Step 5: Setup Semaphore Run the following command to start Semaphore setup in your system.

$ sudo semaphore setup Hello! You will now be guided through a setup to: 1. Set up configuration for a MySQL/MariaDB database 2. Set up a path for your playbooks (auto-created) 3. Run database Migrations 4. Set up initial semaphore user & password What database to use: 1 - MySQL 2 - BoltDB 3 - PostgreSQL (default 1): 1 DB Hostname (default 127.0.0.1:3306): DB User (default root): root DB Password: DB Name (default semaphore): semaphore Playbook path (default /tmp/semaphore): /opt/semaphore Web root URL (optional, example http://localhost:8010/): http://localhost:8010/ Enable email alerts (y/n, default n): n Enable telegram alerts (y/n, default n): n Enable LDAP authentication (y/n, default n): n Confirm these values are correct to initiate setup. Is this correct? (yes/no): yes Config output directory (default /root): WARN[0037] An input error occured:unexpected newline Running: mkdir -p /root.. Configuration written to /root/config.json.. Pinging db.. Running DB Migrations.. Checking DB migrations Creating migrations table ...... Migrations Finished Set username Username: admin Email: admin@example.com WARN[0268] sql: no rows in result set level=Warn Your name: Admin User Password: StrongUserPassword You are all setup Admin User! Re-launch this program pointing to the configuration file ./semaphore -config /root/config.json To run as daemon: nohup ./semaphore -config /root/config.json & You can login with computingpost@example.com or computingpost. You can set other configuration values on the file /root/config.json. Step 6: Configure systemd unit for Semaphore Let’s now configure Semaphore Ansible UI to be managed by systemd. Create systemd service unit file. sudo vi /etc/systemd/system/semaphore.service The add: [Unit] Description=Semaphore Ansible UI Documentation=https://github.com/ansible-semaphore/semaphore Wants=network-online.target After=network-online.target [Service] Type=simple ExecReload=/bin/kill -HUP $MAINPID ExecStart=/usr/bin/semaphore server --config /etc/semaphore/config.json SyslogIdentifier=semaphore Restart=always [Install] WantedBy=multi-user.target Create Semaphore configurations directory: sudo mkdir /etc/semaphore Copy your configuration file to created directory: sudo ln -s /root/config.json /etc/semaphore/config.json Stop running instances of Semaphore. sudo pkill semaphore Confirm: ps aux | grep semaphore Reload systemd and start semaphore service. sudo systemctl daemon-reload sudo systemctl restart semaphore Check status to see if running: $ systemctl status semaphore ● semaphore.service - Semaphore Ansible UI Loaded: loaded (/etc/systemd/system/semaphore.service; disabled; vendor preset: disabled) Active: active (running) since Tue 2022-04-19 13:29:42 UTC; 3s ago Docs: https://github.com/ansible-semaphore/semaphore Main PID: 8636 (semaphore) CGroup: /system.slice/semaphore.service └─8636 /usr/bin/semaphore server --config /etc/semaphore/config.json Apr 19 13:29:42 centos.example.com systemd[1]: Started Semaphore Ansible UI. Apr 19 13:29:42 centos.example.com semaphore[8636]: MySQL root@127.0.0.1:3306 semaphore Apr 19 13:29:42 centos.example.com semaphore[8636]: Tmp Path (projects home) /tmp/semaphore Apr 19 13:29:42 centos.example.com semaphore[8636]: Semaphore v2.8.53 Apr 19 13:29:42 centos.example.com semaphore[8636]: Interface Apr 19 13:29:42 centos.example.com semaphore[8636]: Port :3000 Apr 19 13:29:42 centos.example.com semaphore[8636]: Server is running Set Service to start at boot. $ sudo systemctl enable semaphore Created symlink /etc/systemd/system/multi-user.target.wants/semaphore.service → /etc/systemd/system/semaphore.service. Port 3000 should now be Open $ sudo ss -tunelp | grep 3000 tcp LISTEN 0 128 [::]:3000 [::]:* users:(("semaphore",pid=8636,fd=8)) ino:36321 sk:ffff8ae3b4e59080 v6only:0

Step 7: Setup Nginx Proxy (Optional) To be able to access Semaphore Web interface with a domain name, use the guide below to setup. Configure Nginx Proxy for Semaphore Ansible Web UI Step 8: Access Semaphore Web interface On your web browser, open semaphore Server IP on port 3000 or server name. Use the username/email created earlier during installation to Sign in. Web console for semaphore should be shown after authentication. You’re ready to manage your servers with Ansible and powerful Web UI. The initial steps required are: Add SSH keys / API keys used by Ansible – Under Key Store > create key Create Inventory file with servers to manage – Under Inventory > create inventory Create users and add to Team(s) Create Environments Add Playbook repositories Create Task Templates and execute Also check a detailed guide on semaphore Web UI. For Ubuntu / Debian installation, check: Setup Semaphore Ansible Web UI on Ubuntu / Debian

[viswatechynology]

Dead Lock

What is Deadlock?

Deadlock is a situation that occurs in OS when any process enters a waiting state because another waiting process is holding the demanded resource. Deadlock is a common problem in multi-processing where several processes share a specific type of mutually exclusive resource known as a soft lock or software.

Example of Deadlock

A real-world example would be traffic, which is going only in one direction.

Here, a bridge is considered a resource.

So, when Deadlock happens, it can be easily resolved if one car backs up (Preempt resources and rollback).

Several cars may have to be backed up if a deadlock situation occurs.

So starvation is possible.

Read More

What is Circular wait?

One process is waiting for the resource, which is held by the second process, which is also waiting for the resource held by the third process etc. This will continue until the last process is waiting for a resource held by the first process. This creates a circular chain.

For example, Process A is allocated Resource B as it is requesting Resource A. In the same way, Process B is allocated Resource A, and it is requesting Resource B. This creates a circular wait loop.

Example of Circular wait

For example, a computer has three USB drives and three processes. Each of the three processes able to holds one of the USB drives. So, when each process requests another drive, the three processes will have the deadlock situation as each process will be waiting for the USB drive to release, which is currently in use. This will result in a circular chain.

Deadlock Detection in OS

A deadlock occurrence can be detected by the resource scheduler. A resource scheduler helps OS to keep track of all the resources which are allocated to different processes. So, when a deadlock is detected, it can be resolved using the below-given methods:

Deadlock Prevention in OS

It’s important to prevent a deadlock before it can occur. The system checks every transaction before it is executed to make sure it doesn’t lead the deadlock situations. Such that even a small change to occur dead that an operation which can lead to Deadlock in the future it also never allowed process to execute.

It is a set of methods for ensuring that at least one of the conditions cannot hold.

No preemptive action:

No Preemption — A resource can be released only voluntarily by the process holding it after that process has finished its task

If a process which is holding some resources request another resource that can’t be immediately allocated to it, in that situation, all resources will be released.

Preempted resources require the list of resources for a process that is waiting.

The process will be restarted only if it can regain its old resource and a new one that it is requesting.

If the process is requesting some other resource, when it is available, then it was given to the requesting process.

If it is held by another process that is waiting for another resource, we release it and give it to the requesting process.

Mutual Exclusion:

Read More

Mutual Exclusion is a full form of Mutex. It is a special type of binary semaphore which used for controlling access to the shared resource. It includes a priority inheritance mechanism to avoid extended priority inversion problems. It allows current higher priority tasks to be kept in the blocked state for the shortest time possible.

Resources shared such as read-only files never lead to deadlocks, but resources, like printers and tape drives, needs exclusive access by a single process.

Hold and Wait:

In this condition, processes must be stopped from holding single or multiple resources while simultaneously waiting for one or more others.

Circular Wait:

It imposes a total ordering of all resource types. Circular wait also requires that every process request resources in increasing order of enumeration.

Deadlock Avoidance Algorithms

It is better to avoid a deadlock instead of taking action after the Deadlock has occurred. It needs additional information, like how resources should be used. Deadlock avoidance is the simplest and most useful model that each process declares the maximum number of resources of each type that it may need.

Avoidance Algorithms

The deadlock-avoidance algorithm helps you to dynamically assess the resource-allocation state so that there can never be a circular-wait situation.

A single instance of a resource type.

Use a resource-allocation graph

Cycles are necessary which are sufficient for Deadlock

Multiples instances of a resource type.

Cycles are necessary but never sufficient for Deadlock.

Uses the banker’s algorithm

Advantages of Deadlock

Here, are pros/benefits of using Deadlock method

This situation works well for processes which perform a single burst of activity

No preemption needed for Deadlock.

Convenient method when applied to resources whose state can be saved and restored easily

Feasible to enforce via compile-time checks

Needs no run-time computation since the problem is solved in system design

Disadvantages of Deadlock

Here, are cons/ drawback of using deadlock method

Delays process initiation

Processes must know future resource need

Pre-empts more often than necessary

Dis-allows incremental resource requests

Inherent preemption losses.

[viswatech]

Dead Lock

What is Deadlock?

Deadlock is a situation that occurs in OS when any process enters a waiting state because another waiting process is holding the demanded resource. Deadlock is a common problem in multi-processing where several processes share a specific type of mutually exclusive resource known as a soft lock or software.

Example of Deadlock

A real-world example would be     traffic, which is going only in one direction.

Here, a bridge is considered a     resource.

So, when Deadlock happens, it     can be easily resolved if one car backs up (Preempt resources and     rollback).

Several cars may have to be     backed up if a deadlock situation occurs.

So starvation is possible.

Read More

What is Circular wait?

One process is waiting for the resource, which is held by the second process, which is also waiting for the resource held by the third process etc. This will continue until the last process is waiting for a resource held by the first process. This creates a circular chain.

For example, Process A is allocated Resource B as it is requesting Resource A. In the same way, Process B is allocated Resource A, and it is requesting Resource B. This creates a circular wait loop.

Example of Circular wait

For example, a computer has three USB drives and three processes. Each of the three processes able to holds one of the USB drives. So, when each process requests another drive, the three processes will have the deadlock situation as each process will be waiting for the USB drive to release, which is currently in use. This will result in a circular chain.

Deadlock Detection in OS

A deadlock occurrence can be detected by the resource scheduler. A resource scheduler helps OS to keep track of all the resources which are allocated to different processes. So, when a deadlock is detected, it can be resolved using the below-given methods:

Deadlock Prevention in OS

It’s important to prevent a deadlock before it can occur. The system checks every transaction before it is executed to make sure it doesn’t lead the deadlock situations. Such that even a small change to occur dead that an operation which can lead to Deadlock in the future it also never allowed process to execute.

It is a set of methods for ensuring that at least one of the conditions cannot hold.

No preemptive action:

No Preemption – A resource can be released only voluntarily by the process holding it after that process has finished its task

If     a process which is holding some resources request another resource that     can’t be immediately allocated to it, in that situation, all resources     will be released.

Preempted     resources require the list of resources for a process that is waiting.

The     process will be restarted only if it can regain its old resource and a new     one that it is requesting.

If     the process is requesting some other resource, when it is available, then     it was given to the requesting process.

If     it is held by another process that is waiting for another resource, we     release it and give it to the requesting process.

Mutual Exclusion:

Read More

Mutual Exclusion is a full form of Mutex. It is a special type of binary semaphore which used for controlling access to the shared resource. It includes a priority inheritance mechanism to avoid extended priority inversion problems. It allows current higher priority tasks to be kept in the blocked state for the shortest time possible.

Resources shared such as read-only files never lead to deadlocks, but resources, like printers and tape drives, needs exclusive access by a single process.

Hold and Wait:

In this condition, processes must be stopped from holding single or multiple resources while simultaneously waiting for one or more others.

Circular Wait:

It imposes a total ordering of all resource types. Circular wait also requires that every process request resources in increasing order of enumeration.

Deadlock Avoidance Algorithms

It is better to avoid a deadlock instead of taking action after the Deadlock has occurred. It needs additional information, like how resources should be used. Deadlock avoidance is the simplest and most useful model that each process declares the maximum number of resources of each type that it may need.

Avoidance Algorithms

The deadlock-avoidance algorithm helps you to dynamically assess the resource-allocation state so that there can never be a circular-wait situation.

A single instance of a resource type.

Use     a resource-allocation graph

Cycles     are necessary which are sufficient for Deadlock

Multiples instances of a resource type.

Cycles     are necessary but never sufficient for Deadlock.

Uses     the banker’s algorithm

Advantages of Deadlock

Here, are pros/benefits of using Deadlock method

This     situation works well for processes which perform a single burst of     activity

No     preemption needed for Deadlock.

Convenient     method when applied to resources whose state can be saved and restored     easily

Feasible     to enforce via compile-time checks

Needs     no run-time computation since the problem is solved in system design

Disadvantages of Deadlock

Here, are cons/ drawback of using deadlock method

Delays     process initiation

Processes     must know future resource need

Pre-empts     more often than necessary

Dis-allows     incremental resource requests

Inherent     preemption losses.