Vagrant is a personal tool to automatically provision virtual machine environments. It comes for free along with VirtualBox plugin, although there are commercial plugins for other virtualization engines such as VMWare. It is a very handy tool, especially for developers: it enables them to quickly mock-up or destroy even complex virtual machine environments by executing just one command. Within this post we'll see how easily it can be installed, and how easy it is operating with it.
Every skilled professional should have an understanding of how the kernel does allocate memory: sooner or later it happens to get a system stuck complaining that it cannot allocate memory, despite the output of the "free" command showing that there's plenty of memory. This can get people confused, however this only means that the system cannot allocate kernel memory, despite it can still allocate system memory. The aim of this post is to clarify how the kernel allocates physical memory using the buddy algorithm, along with the available tools to check the state of physical memory.
A pillar every Linux professional must have are certainly Regular Expressions: they are broadly used every time is required to lookup or substitute a pattern that matches some criteria. Tools such as grep and sed miss almost all of their power if who is using them does not have a good understanding of Regular Expressions. This is really a huge topic: there's more than one book that is fully focused on regular expressions - this post is only a quick guide: the aim of this post is to let the reader get the gist of what Regular Expressions are by explaining everything that is needed to know to face the common use cases that may arise during daily work..
When dealing with environments that should meet security regulations it is very unlikely that systems have direct access to the Internet: they connect to the Internet by the means of a content proxy.
When dealing with the need of access the online Ansible Galaxy, you may think that creating the access rule on the corporate proxy is enough to sort things out, but it isn't: besides the poor performances due to the latency for downloading contents from the Internet, there's also the security concern that it is possible to upload contents to Ansible Galaxy using that proxy.
If you are working in an environment with sensitive data, this is a huge security risk that you can mitigate by using an on premise repository manager that mirrors the contents you need from the online Ansible Galaxy.
This post shows you how easily you can mirror a subset of the collections hosted onto the online Ansible Galaxy by using Pulp3 with the Ansible plugin.
Pulp is the repository manager used by Katello (the upstream project of Red Hat Network Satellite server 6.x). This Pulp version is really exciting, since it comes with several plugins that let you host several kind of repositories:
- generic files
- software packages: RPM packages, Deb Packages and even Container Images
- software modules: Python modules, Maven contents, Ruby Gem
- contents configuration management software: Ansible roles and collections and Chef cookbooks
In this post I'll show you how easy it is to install Pulp3 as container using the official container image.