Poland ice-hockey predictions tomorrow

Tactical Adjustments and Coaching Decisions

Critical coaching decisions will play a significant role in tomorrow's matches:

• In-Game Substitutions**: Coaches will need to make timely substitutions to maintain energy levels and exploit weaknesses in opposing defenses.mikkelk/mikkelk.github.io<|file_sep|>/_posts/2018-09-06-Ethereum-Dapps.md --- layout: post title: "Ethereum Dapps" date: "2018-09-06" categories: blockchain ethereum dapp --- # Ethereum Dapps Ethereum is one of several projects aiming at bringing smart contracts onto blockchains. The idea is that anyone should be able develop smart contracts which are then deployed onto blockchains. These smart contracts can then interact with each other using Ether as currency. This makes it possible for developers creating decentralized applications (Dapps) using smart contracts. This blog post gives an overview of Ethereum Dapps. ## Ethereum Ethereum is an open-source blockchain which allows developers write smart contracts. It was first proposed by Vitalik Buterin [1] [2] who later founded Ethereum Foundation which oversees development. The first release of Ethereum was called Frontier [1]. The Ethereum white paper defines Ethereum as: >An Ethereum Virtual Machine (EVM) running on top of this network defines a Turing-complete programming language which enables anyone, regardless of technical ability or resources, to create arbitrarily complex smart contracts [2]. ## Smart Contracts Smart contracts are computer programs stored onto blockchains. The idea is that these programs can interact with each other using Ether as currency. This allows developers build decentralized applications (Dapps). Smart contracts are typically written using Solidity [1] [2]. Solidity is an object-oriented programming language influenced by JavaScript. However Solidity uses static typing instead of dynamic typing. This makes it more similar than JavaScript when it comes down to syntax. ## Decentralized Applications (Dapps) Decentralized applications (Dapps) are applications which use smart contracts instead of centralized servers. The idea is that users can interact with these applications directly without any middlemen or intermediaries. This allows users full control over what happens within these applications. ### Example An example of decentralized application is called CryptoKitties [5]. CryptoKitties allows users buy virtual cats using Ether as currency. The application uses smart contracts deployed onto Ethereum blockchain. Each virtual cat has its own unique ID which acts as its public key. Users can breed two virtual cats together which creates another virtual cat. The ID (public key) of this new virtual cat depends on its parents' IDs (public keys). This makes sure that every virtual cat has its own unique ID. ## Conclusion In conclusion Ethereum allows developers write smart contracts using Solidity language. These smart contracts can then be deployed onto Ethereum blockchain. Once deployed these smart contracts can interact with each other using Ether as currency. This makes it possible for developers create decentralized applications (Dapps). ## References [1] https://www.ethereum.org/ [2] https://github.com/ethereum/wiki/wiki/White-Paper [3] https://en.wikipedia.org/wiki/Ethereum [4] https://solidity.readthedocs.io/en/v0.4.24/ [5] https://www.cryptokitties.co/<|repo_name|>mikkelk/mikkelk.github.io<|file_sep|>/_posts/2018-03-25-Docker-for-Beginners.md --- layout: post title: "Docker For Beginners" date: "2018-03-25" categories: docker container --- # Docker For Beginners Docker is an open-source platform which allows developers build, ship and run distributed applications using containers [1][2]. A container packages an application together with all its dependencies including libraries and system tools required by that application. In this way it becomes easy for developers deploy applications across multiple machines regardless of differences between those machines. ## What Is Docker? Docker is an open-source platform which allows developers build, ship and run distributed applications using containers [1][2]. A container packages an application together with all its dependencies including libraries and system tools required by that application. In this way it becomes easy for developers deploy applications across multiple machines regardless of differences between those machines. ## Why Use Docker? There are several reasons why one would want use Docker: * **Portability:** Applications packaged inside containers can easily be moved between different machines regardless if they run Windows or Linux operating system. * **Scalability:** Applications packaged inside containers can easily scale up or down depending on demand. * **Security:** Applications packaged inside containers are isolated from other processes running on host machine. * **Flexibility:** Applications packaged inside containers can run anywhere including cloud platforms such as Amazon Web Services (AWS) or Google Cloud Platform (GCP). * **Efficiency:** Containers use fewer resources compared with virtual machines (VMs). ## How Does Docker Work? Docker works by creating isolated environments called containers where each container contains everything needed run particular piece software including operating system kernel itself [1][2]. Containers communicate via network interface provided by host operating system so they don't need direct access into underlying hardware like VMs do. When you start up new container instance all necessary files required by application get copied from host machine into newly created container instance. Once started up container instance behaves exactly like regular process running under same operating system kernel but without any direct access into underlying hardware like VMs do. ## How To Install Docker? Installing Docker depends heavily upon operating system being used but generally speaking there are two ways install Docker: 1) Download official binaries from official website [1][2]. 2) Use package manager specific your operating system such as apt-get/yum/etc... Once installed simply run command `docker version` from command line interface (CLI) terminal window should display something similar below: Client: Version: {{ site.docker_version }} API version: {{ site.docker_api_version }} Go version: {{ site.go_version }} Git commit: {{ site.git_commit }} Built: {{ site.built }} OS/Arch: {{ site.os_arch }} Server: Version: {{ site.docker_version }} API version: {{ site.docker_api_version }} Go version: {{ site.go_version }} Git commit: {{ site.git_commit }} Built: {{ site.built }} OS/Arch: {{ site.os_arch }} If everything went well then congratulations! You have successfully installed Docker! ## How To Create Container Images? Container images are created using special tool called `Dockerfile` which contains instructions describing how build particular image [1][2]. A typical `Dockerfile` looks something like below: FROM ubuntu:16.04 RUN apt-get update && apt-get install -y curl vim git CMD ["bash"] Above `Dockerfile` describes how build image based upon Ubuntu Linux distribution version `16.04`. It installs several useful tools such as curl/vim/git before finally starting up bash shell when container instance starts up. To build above image simply run following command from directory containing above `Dockerfile`: docker build -t my_image . Once built successfully you should see something similar below: Sending build context to Docker daemon {{ site.build_context }} bytes Step {{ site.step_one }}/{{ site.total_steps }} : FROM ubuntu:16.04 ---> cdb5f9c7d6b9 Step {{ site.step_two }}/{{ site.total_steps }} : RUN apt-get update && apt-get install -y curl vim git ---> Running in b39e5fca8f7c ... Successfully built e34e6c6b9d7f Successfully tagged my_image :latest If everything went well then congratulations! You have successfully created your first container image! ## How To Run Container Instances? To run new container instance simply execute following command from command line interface (CLI) terminal window: docker run -it my_image /bin/bash Above command tells Docker run new container instance based upon previously created `my_image` image using interactive terminal mode (`-it`) option followed by bash shell executable path (`/bin/bash`) argument passed onto newly created container instance upon startup time. Once started up successfully you should see something similar below: root@{{ site.container_id }}:/# Congratulations! You have successfully started your first container instance! ## How To Stop Container Instances? To stop currently running container instance simply execute following command from command line interface (CLI) terminal window: docker stop {{ site.container_id }} Above command tells Docker stop currently running container instance identified by its unique ID (`{{ site.container_id }}`) passed onto `docker stop` command as argument. Once stopped successfully you should see something similar below: {{ site.container_id }} Stopped Congratulations! You have successfully stopped your first container instance! ## How To Remove Container Instances? To remove stopped container instances simply execute following command from command line interface (CLI) terminal window: docker rm {{ site.container_id }} Above command tells Docker remove stopped container instance identified by its unique ID (`{{ site.container_id }}`) passed onto `docker rm` command as argument. Once removed successfully you should see something similar below: {{ site.container_id }} Removed Congratulations! You have successfully removed your first stopped container instance! ## How To Remove Container Images? To remove previously created container images simply execute following command from command line interface (CLI) terminal window: docker rmi my_image Above command tells Docker remove previously created container image identified by its name (`my_image`) passed onto `docker rmi` command as argument. Once removed successfully you should see something similar below: Untagged: my_image :latest Deleted: sha256:e34e6c6b9d7f... Deleted: sha256:cdb5f9c7d6b9... Deleted: sha256:f6e0d9a9d9f... Deleted: sha256:a0b71c8b5a... Deleted: sha256:a0b71c8b5a... Deleted: sha256:a0b71c8b5a... Deleted: sha256:a0b71c8b5a... Deleted: sha256:a0b71c8b5a... Deleted: sha256:a0b71c8b5a... Deleted: sha256:a0b71c8b5a... Deleted: sha256:a0b71c8b5a... Deleted: sha256:a0b71c8b5a... Deleted: sha256:a0b71c8b5a... Congratulations! You have successfully removed your first previously created container image! ## Conclusion In conclusion Docker provides powerful platform allowing developers easily package applications together along with all necessary dependencies required by those applications into isolated environments called containers which behave exactly