The ramblings of a computer geek
An Autonomous System Number (ASN) uniquely identifies a network or group of IP prefixes under a single administrative control that uses BGP to exchange routing information with other networks. Each ASN is used to tag routes in BGP so that routers can make loop-prevention and policy decisions. When two networks peer, they exchange routes with … Read more
Here’s a quick example of how you can use Terraform’s cidrsubnet function to streamline your use of IP Subnets and calculate a number of different subnets from a single CIDR range (or supernet). https://developer.hashicorp.com/terraform/language/functions/cidrsubnet Explaination The cidrsubnet function can be a bit weird when first looking at it. But we’re going to have an example … Read more
Firstly, a disclaimer. Although you can store values, specifically secrets (e.g. passwords) within Environment Variables so that you are not storing them in your Terraform template code there are better ways, for example by use of a formal Secrets Management solution. However, this article will show you how you can use Environment Variables to “safely” … Read more
We use IaC (Infrastructure as Code) for the deployment and management of all cloud (AWS) workloads to ensure we can manage and update infrastructure and applications that are deployed in the cloud rapidily and on an ongoing basis, while maintaining flexibility, security and availability. However issues may occur when changes are made using automated processes, … Read more
Although you should be using a keypair for SSH authentication (and not exposing to the Internet), if you’re working with a throw-away or test instance you might just need password authentication to be enabled. Here’s how! Open the SSH configuration file. Set the line “PasswordAuthentication” to “yes”. Save and close. Restart the SSH daemon with: … Read more
A potential scenario is to have a single Terraform template repository where you need to manage AWS resources across a number of different AWS Accounts. However, because each AWS Account is the edge of its authentication and authorisation profile, there is a need to be able cross this boundary within your Terraform to be able … Read more
You can force a replacement of an AWS EC2 instance within Terraform by issuing the following command. The previous command “taint” has now been deprecated. Where your instance is called “My-Instance-1” within the Terraform template. When you run this the instance will be destroyed and replaced (as if it was the first time it was … Read more
We have a user which has somehow added a proxyAddress (an email address to their account) but they don’t have an Exchange Online mailbox, and seemingly never have. Microsoft says the following about it from this article: An example of the problem can be seen below, as you can see the object on the right has … Read more
AWS CloudFront allows you to front your application (be it on EC2 instances or REST API etc.) so you can provide high availability, caching and protection (with WAF) to the workload. When configuring your application, you don’t want the application to be directly accessible without using CloudFront, so therefore you need to add some restrictions, … Read more
Here’s a little oddity with AWS Route Tables within Terraform, if you want to remove all of the routes in a route table, you can’t just delete or comment them out, otherwise it treats them as if nothing has changed. See the below example, you comment/remove the routes, then in its place add a blank … Read more