Peter Mescalchin magnetikonline

Delete CloudFormation stack - retaining resources

A guide for removing an existing CloudFormation stack - but retaining all managed resources.

First step - we need to get the CloudFormation stack into a state of DELETE_FAILED. This can be achieved by attempting stack delete with an IAM role that only has IAM action rights to cloudformation:DeleteStack and cloudformation:DescribeStackResources.

Create a new temporary IAM role with only the following allowed policy actions - for the rest of this guide that will be IAM role TEMP_CLOUDFORMATION_ROLE:

Remove AWS network interfaces from security group ID

Script has been handy to clean up security groups which have been used with VPC honed AWS Lambda functions and maintain an ENI association.

Why this is a problem:

Lambda function is created within the given VPC subnet(s) and assigned security group.
During deployment, AWS on your behalf creates ENIs assigned to the security group and placed into the instructed subnet(s).
Next, change is made to Lambda involving new security group association. AWS now creates new ENIs - as ENI reuse between Lambdas is only for the same security group/subnet combination.
Finally, user wishes to clean up legacy security group - but can't as existing ENIs still use security group.

List AWS Lambda@Edge log groups across regions

AWS Lambda@Edge functions, which run under CloudFront at multiple edge locations require associated Lambda functions to exist within each AWS region.

By design, this means CloudWatch Log groups produced by Lambda@Edge functions will exist across these regions.

This Bash script will query for all log groups associated to Lambda@Edge functions for each enabled region of the current AWS account to hopefully help determine where logs are going to and/or exist.

Delete S3 versioned objects and delete markers

Quick and dirty Bash script to iterate an S3 bucket and remove all object versions and delete markers.

Probably only usable on buckets with a few hundred version objects maximum, otherwise it might be more efficient and time effective to use a lifecycle rule to age out and remove objects in bulk.

Reference

https://gist.github.com/weavenet/f40b09847ac17dd99d16

Install The Silver Searcher (`ag`) on macOS from source

A quick n' dirty bash script to install the following:

automake, pkg-config, PCRE, xz - all needed by ag configure.
ag - from source.

Requires as a minimum Xcode CLI tools (don't need a full Xcode install). Can be done via the following:

$ xcode-select --install

Golang net/http middleware flow

$ go run main.go
Called middleware03()
Called middleware02()
Called middleware01()
Called initial()

Golang private modules within a GitHub organization

You've got Golang modules within a private repository or an organization and would like to go get them.

For this example the GitHub organization will be spacely-sprockets.

Howto

Set GOPRIVATE (ideally placed in your .bashrc / dotfiles):

Find latest non beta/RC release for Docker CLI

Using curl and jq to:

Pull list of GitHub release tags.
Filter out all that don't match vX.Y.Z (stripping beta/rc).
Finally return just the first entry (latest tag).

$ curl --silent \

Creating a 'run once' systemd unit

Systemd unit template which calls a script exactly once upon startup and keeps unit status active after script finishes.

Unit file placed in /etc/systemd/system and enabled with:

$ sudo systemctl enable runonce.service
$ sudo systemctl start runonce.service

	name: Workflow

	on:
	push:
	branches:
	- main

	jobs:
	first:
	runs-on: ubuntu-latest