Replay - Colasoft's MAC Scanner

 

Very effective way to find out the MAC and IP addresses on your subnet when devices have firewalls blocking icmp or pings is to run an arp scan.

In this video i used Colasoft's MAC SCANNER you can find this at https://www.colasoft.com/mac_scanner/

We Know What Causes That

 

Dr. Franz H. Messerli, a recognized expert in hypertensive cardio-vascular disease, has published over 600 papers and written 20 books. In 2012, in the prestigious New England Journal of Medicine, Dr. Messerli wrote a short article about Nobel prizes and chocolate consumption. His research uncovered a strong linear correlation (r=0.791, P<0.0001) between the number of Nobel laureates a country produced per capita and the average chocolate consumption. He noted a possible link between dietary flavonols in chocolate and the reversal of age-related cognitive impairment. In order to think more clearly, he suggested, people everywhere should eat more chocolate.

While the article was intended as a funny reminder not to allow correlations to lead to false claims, not all of Messerli’s colleagues appreciated the humor. Many complained that the New England Journal of Medicine would publish such a thing, rushing to discredit the idea that eating chocolate would lead to more Nobel prizes. One even noted that there was a strong correlation between the number of IKEA stores and Nobel Prizes in a country, although offering no suggestions as to why that might be. If you’ve ever assembled IKEA furniture, you might have some ideas on this.

Food correlations are popular because we all eat. If eating chocolate in search of a Nobel Prize is not your thing, perhaps getting a doctorate in Civil Engineering piques your interest. Data shows a correlation (r=0.958) between the per capita consumption of mozzarella cheese and the number of CE PhD’s awarded. Since mozzarella is a key ingredient of pizza, this may explain its legendary popularity with graduate students.

Some of us are old enough to remember another popular correlation - the so-called “Hemline Index”. Economist George Taylor is often given credit, but while his 1929 thesis on post-war economic growth connected it with skirt length, he never proposed a general theory. As recently as 2010, economists Marjolein van Baardwijk and Philip Hans Franses of the Erasmus School of Economics examined this urban legend in light of hemline data from 1921-2009.

The accepted premise was that in prosperous times, people feel good and skirts get shorter, while empty bank accounts spoil the fun and cause hemlines to drop. The researchers were focused on the historical periods where the theory didn’t appear to hold. Their data analysis indicated that the economy leads the skirt length by about 3 years, although the conclusions were somewhat confounded by the weather. Even a full bank account doesn’t necessarily prompt a woman to wear a mini-skirt in the winter.

Not all researchers spend their working hours munching on pizza and chocolate while studying women’s skirts, although I’m not ruling out the possibility of finding data to support that conclusion. The Internet offers plenty of strange correlations, many of which should (but don’t always) fail the common-sense test.

As a kid growing up, I always looked forward to summers – you got 3 months off school and could do pretty much whatever you wanted while your parents provided free room and board. The other great thing about summers was that as the temperatures rose, the ice cream truck began making its daily rounds through our neighborhood. My Dad would grumble about how the ice cream truck’s wares were overpriced, so he would always lay in a summer stock of ice cream in our freezer. Confirmation bias notwithstanding, I just know that hot weather and ice cream sales have a strong positive correlation.

Mention hot weather to anyone in law enforcement, and I doubt if ice cream is the first thing that comes to mind. It is a proven fact that hotter weather begets higher crime rates – violent crimes in particular. Causation theories on this abound – increased levels of hostility and aggression, more social encounters that could turn violent, teens out of school with little to do and no supervision – people might even be fighting over ice cream.

It's easy to see how the comparison of two simple data sets, widely available on the Internet, can lead to some crazy theories. Comparing crime rates to ice cream sales would show a positive correlation, leading one to believe that eating ice cream makes one prone to criminal acts. Similarly, rising utility bills from increased air conditioner use would appear to make us more violent, at least until we identify the third variable – temperature. You get the idea.

At one time or another, most of us have been introduced to the Birthday Paradox. The basic idea is that if you have 23 or more people gathered together – like at a cocktail party or in a classroom – the odds are better than 50-50 that two will share the same birthday. The math is straightforward, although the result is quite counterintuitive. Someone inevitably points out that all birthdays are not equally likely, which is true, but has little effect on the outcome.

If you’re curious, the month with the most birthdays is August. Counting back 9 months puts us into the holiday parties, cold weather and cozy fires of December, a perfect setting for starting a baby.

And we know what causes that.

Author Profile - Paul W. Smith - leader, educator, technologist, writer - has a lifelong interest in the countless ways that technology changes the course of our journey through life. In addition to being a regular contributor to NetworkDataPedia, he maintains the website Technology for the Journey and occasionally writes for Blogcritics. Paul has 50 years of experience in research and advanced development for companies ranging from small startups to industry leaders. His other passion is teaching - he is a former Adjunct Professor of Mechanical Engineering at the Colorado School of Mines. Paul holds a doctorate in Applied Mechanics from the California Institute of Technology, as well as Bachelor’s and Master’s Degrees in Mechanical Engineering from the University of California, Santa Barbara.

Taking Kubernetes for a Spin: Beginner's Guide to kubectl

 

What Is kubectl?

Kubectl is a command-line interface (CLI) for running commands against Kubernetes clusters. It allows developers and administrators to interact with the Kubernetes API Server, which is the central management entity in a Kubernetes cluster. The name "kubectl" is derived from "kube CTL," where "kube" is short for Kubernetes and "CTL" is short for control.

Kubectl provides a way to manage your Kubernetes objects and resources. Whether you want to create, view, update, or delete Kubernetes pods, services, volumes, or deployments, kubectl has got you covered. It's a swiss army knife of sorts for interacting with Kubernetes, providing the ability to perform a wide range of tasks.

In the following sections we’ll provide a quick start guide to kubectl. See this blog post for a full kubectl cheat sheet for more advanced users.

Installing and Setting Up kubectl

Installing kubectl involves downloading the latest release with the command:

curl -LO https://storage.googleapis.com/kubernetes-release/release/$(curl -s https://storage.googleapis.com/kubernetes-release/release/stable.txt)/bin/linux/amd64/kubectl

After downloading, we need to make the kubectl binary executable with the command chmod +x ./kubectl.

Next, we move the binary into our PATH with the command sudo mv ./kubectl /usr/local/bin/kubectl.

To test the installation, we run the command kubectl version --client. The output will show the version that has been installed.

Setting up kubectl to interact with your Kubernetes cluster involves creating a kubeconfig file, which provides the necessary details about your cluster, user, namespace, and authentication mechanisms. Usually, when setting up a Kubernetes cluster, the setup process will generate this kubeconfig file for you. For multiple clusters, you can manage different kubeconfig files and switch between them using the KUBECONFIG environment variable.

Basic Operations with kubectl

Creating and Managing Kubernetes Objects

Kubernetes objects like Pods, Services, Deployments, etc., are fundamental building blocks of the Kubernetes system. These objects represent the state of your cluster and kubectl allows you to create and manage these objects.

Creating Kubernetes objects using kubectl often involves writing a configuration file in YAML or JSON format that describes the desired state for the object. For instance, to create a Deployment, you would write a Deployment configuration file and then use the command kubectl apply -f ./my-deployment.yaml to create the Deployment.

Managing Kubernetes objects involves several operations like viewing, updating, and deleting objects. The kubectl commands for these operations are kubectl get, kubectl edit, kubectl delete, respectively.

Viewing and Inspecting Resources

kubectl provides a wide range of commands to view and inspect your Kubernetes resources. The kubectl get command is one of the most used commands. It lists one or more resources of a specific resource type. For example, kubectl get pods will list all the Pods in your current namespace.

For detailed information about a specific resource, you can use the kubectl describe command. This command shows the detailed state of an object, including its specs and status.

Furthermore, you can use the kubectl logs command to fetch the logs of a Pod, which can be crucial for debugging purposes.

Working with Pods and Deployments

Pods and Deployments are two of the most common Kubernetes objects you'll work with. A Pod represents a single instance of a running process in your cluster and can contain one or more containers. A Deployment is a higher-level concept that manages Pods and provides features like scaling and rolling updates.

Creating and managing Pods and Deployments is similar to other Kubernetes objects. You write a configuration file and use kubectl apply -f ./my-pod.yaml or kubectl apply -f ./my-deployment.yaml to create a Pod or Deployment, respectively.

Scaling a Deployment involves updating the number of replicas in the Deployment configuration or using the kubectl scale command. For instance, kubectl scale deployment my-deployment --replicas=3 will scale your Deployment to have three Pods.

Using kubectl for Logs and Debugging

Logs are an essential part of any application. They provide valuable insights into the application's behavior and are crucial for debugging. Kubernetes and kubectl provide several mechanisms for logging and debugging your applications.

The kubectl logs command allows you to fetch the logs of a Pod. For instance, kubectl logs my-pod will fetch the logs of the Pod named my-pod. If your Pod has multiple containers, you can specify the container with -c.

Debugging in Kubernetes often involves interacting with your Pods. The kubectl exec command allows you to run commands in a container. For instance, kubectl exec my-pod -- ls / will run the ls / command in your Pod.

Best Practices for Using kubectl

Like any tool, kubectl is most effective when used correctly. There are certain best practices that can help you get the most out of kubectl.

Use Aliases and Autocompletion

If you're using kubectl frequently, you might find yourself typing the same commands over and over again. This can be tiresome and inefficient. Luckily, kubectl supports aliases and autocompletion.

Aliases are shortcuts for long commands. For instance, you can create an alias "kd" for "kubectl describe". This way, instead of typing the whole command, you just need to type "kd". This can significantly speed up your workflow.

Autocompletion, on the other hand, saves you from having to remember and type out the entire names of your Kubernetes resources. With autocompletion enabled, you just need to type the first few characters of the resource name, and kubectl will automatically fill in the rest. This not only speeds up your work but also reduces the chance of errors.

Prefer Declarative Management for Complex Tasks

While kubectl provides both imperative and declarative ways to manage Kubernetes resources, it's generally recommended to prefer declarative management for complex tasks.

In imperative management, you give kubectl commands to perform actions on resources. For instance, you might use kubectl create to create a new pod, or kubectl delete to delete a pod.

In contrast, declarative management involves creating a file that describes the desired state of the resources, and then using kubectl apply to enforce that state. This approach is more robust and scalable, as it allows you to manage complex systems with many interdependent resources.

Use Labels and Selectors for Efficient Resource Management

Labels and selectors are a powerful feature of Kubernetes that can make your resource management more efficient. Labels are key-value pairs that can be attached to Kubernetes objects, while selectors are expressions that match objects with certain labels.

By labeling your resources, you can easily group and select them based on their labels. For instance, you might label all your frontend pods with "tier=frontend", and then use a selector to select all the pods with this label. This can be incredibly useful for managing large or complex systems.

In conclusion, kubectl is a potent tool for managing Kubernetes clusters, but like any tool, it requires a bit of learning and practice to use effectively. By following the best practices discussed above, you can make your work with kubectl more efficient and enjoyable.

Author Bio: Gilad David Maayan

Gilad David Maayan is a technology writer who has worked with over 150 technology companies including SAP, Imperva, Samsung NEXT, NetApp and Check Point, producing technical and thought leadership content that elucidates technical solutions for developers and IT leadership. Today he heads Agile SEO, the leading marketing agency in the technology industry.

LinkedIn: https://www.linkedin.com/in/giladdavidmaayan/