github ssh keys are finicky

 Okay, github uses some hash magic to figure out what account is affiliated with a particular ssh key. If you have two accounts using the same key, it has to guess (and does so poorly) about which user is trying to write.

Moreover, it tries keys somewhat sequentially. If the first in our ssh-agent (via ssh-add -L) is associated with a user, that's the only one it tries. If not, I believe it will go onto the next one (but again, if that second key is associated with multiple github users, it's going to hash to a specific user.) This is all because you can't tell github what user to use. De facto, the key is hashing to one and only one user and it ass/u/mes that is the user it will end up using.

But, the sad sad sad part is that it will not give you any more information.

You can set a specific "id" to use in our .ssh/config file like this:

Host github.com

Identityfile /home/USERNAME/.ssh/id_githubonly_rsa

 

 

elevator=none elevator=noop are both overcome by events

 You can't just pass in on the kernel commandline "elevator=none". If you do in ~5.3 or newer, you'll see:

[    0.105899] Kernel parameter elevator= does not have any effect anymore.

               Please use sysfs to set IO scheduler for individual devices.

xorriso is the bomb

 So, I wanted to remaster the SystemRescue iso. A trivial (20 character addition) was needed. I could not for the life of me figure out how to do this.

The answer (after 3-4 different multi-hour sessions trying to figure this out) was to use a tool called: xorriso. And to bear in mind that the iso itself needs to be bootable via an ISO or burnt CD/DVD as well as via UEFI and possible even via USB. This means it needs to be an everything bagel (so to speak). I found the "howto" for another distro and used that technique with the slight differences for the system rescue iso (which buries the efiboot.img under archiso since it is arch linux based.)

There was also this handy little guide re: xorriso. That was part of figuring this out. (I've always used genisoimage and friends prior to needing to remaster this.)

ugly code that works

 I had the thought, "ugly code that works", as I finished a PR today. Project isn't technically open sourced (YET!) so I can't say much more but man, I worked sooooo long and hard on this trivial problem that I needed to vent.

The solution to the problem was to do something in cloud-init. Do the same thing in a systemd unit. And all of that was just to work around a sysctl issue. The solution is ugly code that works (in particular as it has a sleep 180 embedded in a script.) There is no reason in the world that I should be writing a systemd unit that calls a two line script where one line is sleep 180. But, there was no way to get the sysctl working with a systemd.path unit. (I tried, repeatedly.)

And the code works. I also then (after getting a merge) googled, "ugly code that works", and saw someone has already written this blog (though thankfully it wasn't me this time). See: https://dev.to/tonetheman/ugly-code-that-works-4i7l

"Do not be afraid to write ugly code that works." Also, don't be too surprised if it does break. Ugly code can be fragile also.

terraform is logical but not natural

The subject kind of says it all. If you can use environment variables (and you can and probably should) in terraform with the invocation/usage of TF_VAR_environment_variable_name, why in the ever loving world can you not do the same in modules (or sub-modules as I think of them)? Apparently environment variables don't propagate into the submodules.

So, you basically "re-declare" when you define/invoke the submodule. See: https://stackoverflow.com/questions/53853790/terraform-how-to-pass-environment-variables-to-sub-modules-in-terraform

In my case, I'm building "N" VMs in submodules and there is a "vms.tf" that has the "module "NAME" {} invocation (and of course there are "N" of these) so I had to do something like:

module "FIRST" {variableone = var.variableone}

.

.

.

module "NTH" {variableone = var.variableone}

"N" times and then at the top level (main.tf or variables.tf) something like:

variable "variableone" {
  description = "Cascade environment variable in terraform"
  default = ""

}

and then
export variableone="myvaluegoeshere"

in my environment.

It's been a minute and a few years....

 So, I just noticed it's been a minute since I last posted. I typically only post things that I need to find again in the future--and apparently that's been less often lately.

Today, I needed to figure out WHY IN THE WORLD my LG 4K HDMI monitor was popping throughout the day. And, indeed I did, but first, how did I get here?

I am a longtime Ubuntu user. This machine was built with Ubuntu in 2017-11 and upgraded to LTS release in 2018. I do daily apt updates but recently bit the bullet and brought it up to 2020 LTS release. That went very well and I see a number of improvements. However, it also started making a LOUD popping noise that I couldn't tie to any particular user activity.

A bit of googling later and I found that it was likely related to snd_hda_intel module and its power_save settings. power_save defaults to 1 (on this machine and similar) as it is a laptop and power_save is a good thing for a laptop. However, 98% of the time, it is now running primarily as a desktop. You know, COVID-19 and nowhere to go....

I confirmed the issue by further googling and found my friend Major Hayden's post when I ran into this same thing: https://major.io/2019/03/04/stop-audio-pops-on-intel-hd-audio/ it has a better writeup, more detail etc. But I post here so that I can easily find this myself for future me. I also thanked past Major here: https://twitter.com/davidmedberry/status/1371588276176363521