Welcome to My Technical Blog
Welcome to my technical blog! I’m Xavier Lopez, a Senior Platform Engineer with over 10 years of experience in DevOps, cloud architecture, and platform devel...
Blog Posts
2024
2023
Network Concepts
Layer 2 and 3 of the Open Systems Interconnection (OSI) Model. An explainer. Data Link Layer (Layer 2): Functionality: This ...
Virtualization - Server
The Fundamentals of Server Virtualization: Benefits Efficiency: Scaling by creating new VMs from templates. Scaling by cloning VM...
Virtualization - Network
Network Virtualization Virtual Switches Virtual Firewalls Virtual NICs These map back to physical network adapte...
Virtualization - CPU
Device mapper: A virtual block device driver framework provided by the Linux kernel, which provides an infrastructure to filter I/O for block devices (BIO...
Useful Commands
Top provides a dynamic real-time view of a running system. PID (Process ID): The unique identifier for each process. USER: The user or ow...
Python
Programming Concepts Instance methods: methods that can be called on instances of a class. They must accept a reference to the actual instance on which it...
Network Troubleshooting
Methodology Identify the problem Gather information Identify symptoms Question users Change ma...
Host Storage Management
Linux Modules: Code segments that can be dynamically loaded and unloaded into the kernel. They can be removed when they are no longer needed. Modules exte...
Host Memory and CPU Troubleshooting
Install and enable sysstat systemctl enable --now sysstat systemctl status sysstat Enable sysstat data collection su...
Ansible
Concepts Modules Discrete units of code that can be used from the command line or in a playbook task. Ansible executes each module, usually on the remote ...
Welcome to Jekyll!
You’ll find this post in your _posts directory. Go ahead and edit it and re-build the site to see your changes. You can rebuild the site in many different wa...
Kubernetes Cluster Configuration
I was in the process of installing Prometheus and needed to have a couple of features enabled in an on-premises cluster, but didn’t know where to get and set...
Create a New Git Merge Request on the Command Line
Let’s create a merge request from the command line. You can do this in the Gitlab UI, but why change contexts? As a developer, you’re familiar with the wor...
2022
Authenticating Gitlab-Runner to Kubernetes
Gitlab-Runner Can’t Talk to the K8s API
Three useful FZF commands
If you haven’t yet discovered fzf, you should take a few minutes of each day to get it under your control. It’s a tool that could add substantial time saving...
How to use Kubernetes secrets for Rails App configuration
For Rails apps that I deploy to a Kubernetes cluster, I like to push as much environment configuration as I can to Kubernetes secrets. Here’s what my app-co...
AWS tag filtering using Terraform data source
This is how you filter an AWS resource, by tag. I needed to do this in order to add a route through a vpc peering connection, for each route table. I wanted ...
Kubernetes Manual Certificate Update and Upgrade-bug Fixes
About one year ago, I set up an on-premises Kubernetes cluster. Keeping track of the SSL certs slipped my mind, and I woke up one morning to an inaccessible ...
Fetch the latest Gitlab repo signing key
This is something I had to track down recently. If you haven’t seen it yet, you will. I know I’m going to need to refer back to it, before all my servers ar...
Tmux Cheatsheet
List tmux sessions:
VIM Cheatsheet
Everyone is already familiar with the basic stuff. If not, you can find it anywhere on the web. I’m going to list some of the hard-to-remember stuff that acc...
Docker Cheatsheet
Yet another cheatsheet! This is coming in handy, isn’t it? Let’s start this off with one that is relatively new to me, and wonderfully useful.
Key and Certificate Extraction from a .pxf file
Sometimes you ask someone in your IT department for an SSL certificate to use in a project you have running somewhere on the internet. He obliges. You feel...
Kubernetes Cheatsheet
You know how we do it. We do a hundred things a day, but we don’t try to memorize it all. For this, we have cheatsheets. Here’s another one.
Display verbose output during ‘vagrant up’
Today, I was running the ‘curl’ command, as part of the provisioning of a Vagrant vm. It was failing, and I couldn’t tell why, because there wasn’t enough in...
RVM Cheatsheet
Let’s create a handy little list of my most commonly used rvm commands. RVM, for those who might be wondering, is a ruby version manager. It does a great job...
Order ls command output by date
The other day I needed to manipulate some files I’d just downloaded from an s3 bucket. Listing the contents of the downloads directory revealed a huge chall...
See Git Log in Glorious Detail
The Git subcommand that I’m about to share with you is so esoteric and its output so detailed, that it inspires developers to build entire user interfaces. ...
Run a Rails App Without a Database
Haven’t you ever wanted to create a Rails application without a database? Installing the default SQLite database, or choosing a different one, and installing...
Can’t find the libpq-fe.h header
This sometimes happens when you try to install the pg gem on a linux box.
Shrink SQL DB log file
Before copying a database to another server, it’s a good idea to shrink the log file for transport. Open SQL Server Management Studio and run the following c...
systemd cheatnotes
systemd is a system and service manager that’s on its way to becoming the default initialization program across linux distributions. The command line starts ...
Save file in VIM without sudo
I cringe every time vim notifies me that I won’t be able to save the file I’ve just edited, after I’ve already changed it in 10 different places.
Unicorn Restart
Every now and then you have to restart your Rails applications. Something happens somewhere along the chain and you start getting screenshots from your coll...
Active Record - Query Only the Columns You Want
Here’s another bit of command line usefullness that I repeatedly need, but never remember. It does a great job of making the query result readable, and unclu...
Skip the pipeline when pushing to Git
Sometimes you don’t want to trigger an entire pipeline run, right? Maybe you’ve only changed the name of some files in the repo, or perhaps you deleted some ...
How to delete a local and remote Git branch
I need to do this often, but not often enough to memorize the process. So I’ll document it here, where I can easily find it.
This is it!
Hello there. This is the first post of the new zavestudios. You have no idea how many times this idea has false started. This time, though, is for real. Firs...
2021
File Archiving and Compression Cheatsheet
TAR - Tape Archive Tool found in Linux / Unix