There will be times when you will be wanting a particular program, header, or library, but aren’t sure which package it is in. Instead of trying to search the repositories for packages by name and description with dnf search, you can use dnf provides to search the repository for packages that provide a particular file.… Read More »
I chose this topic because SEO tools found it is a common search topic. The answer you need is there are multiple variants of Linux for loops. The technically correct answer is there isn’t such a thing, as Linux is just a kernel. The answer you want is how to use a Linux for loop.… Read More »
Creating a simple Linux cluster doesn’t have to be complicated. Below, I demonstrate how to do so with keepalived, named, and nginx. The clustered service will be nginx. I will use named to return virtual IPs (VIP)s when clients lookup the name of the clustered services. Keepalived will be used to manage VIP failover. Server… Read More »
Mirroring an Existing LVM Volume is pretty straightforward. Assuming you have enough space for it on separate physical volumes, it is a single command. According to the documentation, you will find two varieties. One is just called mirror, the other raid1. The documentation recommends using raid1, so that is what I will cover. There are… Read More »
There may be occasions where you need to remove an LVM disk. Maybe the host is a VM and you need space on the hypervisor? Perhaps the device is a fiber channel SAN target that you no longer need? No matter the reason, it isn’t terribly difficult to remove an LVM disk. There are three… Read More »
While uncommon, sometimes a package update can cause problems. Distributions that use yum or dnf track package changes with a transaction log. You can undo a yum update by undoing the relevant transaction(s). In order for this to work, the previous versions of any packages in the transaction must exist in the repositories. The process… Read More »
If you are writing a startup or monitoring script, you may want a way to check if a TCP port is listening in bash. You can actually do it without calling any external programs, such as ss or netstat. I have only done this on Linux, so if you are using another UNIX like operating… Read More »
Linux setuid and setgid programs allow a regular user to alter the user or group it runs as. Below, I provide a program written in C to demonstrate the concepts. Don’t worry if you aren’t a programmer or have good grasp on C. I will walk you through how the program works. I am assuming… Read More »
Using a proxy with DNF is straightforward. You can edit /etc/dnf/dnf.conf, set the relevant environment variable, or use the shell sub command. DNF supports both HTTP and SOCKS proxies and several authentication methods. Keep in mind a few things when caching package repositories: Package repositories running on HTTPS cannot be cached without something like Squid’s… Read More »
The easiest way to tell which shell you are using is by looking at what the exe link points to in your shell process’s /proc directory. You can use the command ls -l /proc/$$/exe. Below is an example: $ ls -l /proc/$$/exe lrwxrwxrwx 1 tyler tyler 0 Sep 22 19:39 /proc/19867/exe -> /bin/bash The special… Read More »