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What are Context Managers? Context managers are constructs that allow you to set something up and tear something down automatically, by using using the statement – with. For example you may want to open a file, write to the file, and then close the file. Here is an example of a context manager, with open(path, … Read more
An abstract class can be considered a blueprint for other classes, allowing you to mandate a set of methods that must be created within any child classes built from your abstract class. Creation Lets first look at how you create an abstract class. First we import abc, we define the class as a metaclass using … Read more
Issue When executing Yum you receive the following error, [root@william-gce blog]# yum install npm rpmdb: Thread/process 3934/139752225695488 failed: Thread died in Berkeley DB library error: db3 error(-30974) from dbenv->failchk: DB_RUNRECOVERY: Fatal error, run database recovery error: cannot open Packages index using db3 – (-30974) error: cannot open Packages database in /var/lib/rpm CRITICAL:yum.main: Error: rpmdb open … Read more
Recently I’ve discovered that there is, well, fairly limited information online around this point. In this short article we will explain how ICMP inspect, whether disabled or enabled, affects the connection table. What is ICMP Inspect? “The ICMP inspection engine allows ICMP traffic to be inspected like TCP and UDP traffic. Without the ICMP inspection … Read more
Introduction The other day I was asked to design a solution that required VNet peering, after some further digging and research into this feature I thought I’d share some of my findings with you all. Before we dive into the pros and cons, lets take a moment to quickly recap on what VNet peering actually … Read more
AWS Identity and Access Management (IAM) is a web service that helps you securely control access to AWS resources for your users. You use IAM to control who can use your AWS resources (authentication) and what resources they can use and in what ways (authorization)[1]. Key features The key IAM features are, Provides centralized control … Read more
AWS provides a suite of application services, such as SQS, SNS, SES and SWF. Each service providing various features and rich toolsets to empower the development and design of your applications. SQS (Simple Queue Service) SQS is a web service that provides access to a distributed message queue. Messages are stored in the queue, these … Read more
Docker provides various commands/methods for moving containers. Within this article we will look at each of the commands, along with examples needed to move your Docker containers between your hosts and repositories. Repo to Repo Lets look at how we get an image from a repository and how we get our local image up to … Read more
Issue When running Docker you may experience the following error, root# docker images Cannot connect to the Docker daemon. Is the docker daemon running on this host? Solution To start the Docker daemon run the following commands. docker-machine start default eval ‘docker-machine env default’ Below is an example, root# docker-machine start default Starting “default”… (default) … Read more