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Hello, My name is Amit - I am interested in programming, software tools, systems and infrastructure. A lot of what I explore in software makes it to my blog posts, articles, books, talks and GitHub repositories. If you would like to get an email everytime I write something new, please subscribe to my newsletter. You can contact me via email, on Twitter and on LinkedIn.

Blog posts

My post recent posts are below. So far, I have written about C, Fedora, Golang, Infrastructure, Python and various others.

AWS VPC subnets and Internet connectivity over IPv4

We can have two kinds of subnets inside a AWS VPC - private and public. A public subnet is one which is attached to an Internet Gateway. This essentially adds a routing table entry to the subnet's routing table sending all Internet traffic to an Internet Gateway. On the other hand …


flyway baseline: Introducing flyway migrations into existing database

If you are trying to introduce flyway to an existing database with the schemas and tables already created, you may find flyway baseline command useful.

Let's say you already have the migration scripts written, or perhaps dumped out of your existing DB setup, and they are:

V1__foo.sql
V2__foo_new.sql …

Git: Staging partial changes in a file

Let's say you have made a few changes to a file and only want to stage only some of those changes for commit. You may want to do so either to create a nice commit history or may be you just want to discard some of the changes. Either way …


Building Fedora Vagrant boxes for VirtualBox using Packer

In a previous post, I shared that we are going to have Fedora Scientific Vagrant boxes with the upcoming Fedora 29 release. Few weeks back, I wanted to try out a more recent build to script some of the testing I do on Fedora Scientific boxes to make sure that …


flyway, SQL server and non-empty schema?

While attempting to use flyway for SQL server schema migrations, I was consistently getting an error of the form Found non-empty schema xxx ithout metadata table! Use init() or set initOnMigrate to true to initialize the metadata table.. Okay, so easy - let me just delete the tables, drop the schema …


Examples of consuming data in Golang templates

While working on creating a template file for a Golang project, I wanted to better understand how to work with data in Golang templates as available via the html/template package. In this post, I discuss a few use cases that may arise.

Accessing a variable

Let's consider our first …


Download a file using `curl` - How hard can it get?

I wanted to download the prometheus binary using curl. My first attempt:

$ curl https://github.com/prometheus/prometheus/releases/download/v2.4.0/prometheus-2.4.0.linux-amd64.tar.gz
<html><body>
You are being <a href="https://github-production-release-asset-2e65be.s3.amazonaws.com/6838921/5c87dc00-b5d1-11e8-8a3a-fd29b54e0c60?X-Amz-Algorithm=AWS4-HMAC-SHA256&amp;X-Amz-Credential=AKIAIWNJYAX4CSVEH53A%2F20180914%2Fus-east-1 …

Docker userns-remap and system users on Linux

In this post, we learn how we can make use of docker's user namespacing feature on Linux in a CI/build environment to avoid running into permission issues. Using user namespacing also keeping things a bit sane without adopting sub-optimal alternatives.

Introduction

Let's consider that we are leveraging docker …


AWS Private Route53 DNS and Docker containers

AWS Route 53 private hosted zones enable you to have private DNS names which only resolve from your VPC. This is great when working from EC2 instances since everything is setup and ready to go. This however becomes a problem when using docker containers on a systemd system. On such …


AWS Network ACLs and ephermal port ranges

In this post, I discuss a problem (and its solution) I encountered while working with AWS (Amazon Web Services) Network ACLs, docker containers and ephermal port ranges.

Infrastructure setup

A Linux EC2 instance with docker engine running in a VPC with inbound and outbound traffic controlled by Network ACLs. I …

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