Everyday Notes from a Linux Administrator
The sed utility can be used to print the contents of a
file, substitute a line (or multiple lines), and then save the file. In
contrast to grep, sed can substitute a line or multiple lines in a file and perform an in-place update of that file.
The simplest sed invocation when substituting foo for bar is:
$ sed 's/foo/bar/' inputfileEvery Linux command has one or more options and flags to perform different operations. One of the useful and important option allow us to simulate Linux commands but do not actually change the system. For instance, we can simulate the process of installation or removal of a package or program, but without actually installing or removing the intended package from a Linux system.
Continue reading “How To Simulate Linux Commands”Missing rc.local for adding commands to run on startup? Here’s how to set up similar functionality with today’s systemd.
The rc.local file was—and in some cases still is—the place for Linux sysadmins to put commands that need to be run at startup. Use of the rc.local
file is not only deprecated but after a couple of hours worth of
attempts, was not working in any event. This despite the fact that the systemd documentation mentions the use of a “generator” that generates systemd services from an rc.local file if one exists.
Docker is the most popular container technology. It is designed to make it easier to create, deploy, and run applications by using containers. Docker behaves similar to a virtual machine hypervisor. But unlike a virtual machine, rather than creating a whole virtual operating system, Docker allows applications to use the same Linux kernel as the system that they’re running on and only requires applications be shipped with things not already running on the host computer. This gives a significant performance boost and reduces the size of the application.
Continue reading “Essential Docker commands”This is the part one of the four part series on the basics of how to use Ansible. There will be a gradual introduction from basic to intermediate examples how to install, setup and use Ansible. As well as the how to create ansible playbooks and roles. Let’s get started with Part One: Installation and Setup.
Continue reading “Ansible Part I: Installation and Setup”