Those are often pretty heavily guarded documents. Here are a couple templates that I found from a Google search. https://sites.radford.edu/~softeng06/SoftwareRequirements.doc https://www.fdot.gov/docs/default-source/it/pdm/3_requirements/System_Requirements_Template.docx More on reddit.com

I find that if I'm struggling to start with documenting something, putting in the following headings as a scaffold helps to give me the shove that I need: Introduction Who What When Where Why How Resources Troubleshooting The Introduction is the executive summary, and you can start with that if you like - it's living documentation so you can always update this section. You will likely find that as you flesh out other parts of the documentation, that your understanding of the material tightens up a bit, and you can go back to the Introduction section and adjust it for accuracy. (Technically speaking, the Introduction should itself contain "the Five W's" (and one H) in some form, as "the Five W's" is a journalism technique where the crucial information is put into the first paragraph.) As you work through each of the Five W headings, they should naturally evolve into other words that make more sense relative to the context. Some of them you may find logically merge together, or some of them you may logically find are not actually necessary. Or the order of them may change etc. The Resources section is usually for referencing any sources you may have used while writing the documentation, and/or for links that a reader may want to follow should they be inspired to dive down the rabbit hole that your documentation has just waved in their face. Once I've got any momentum with writing documentation, I can easily slip into a flow state and smash out dense, yet structured and digestable documentation. I recently wrote a document about how to make bulk changes across our codebase, which means using an API to get a list of all resources from our git server, downloading everything, identifying where the changes need to be made, making feature branches, making the changes, committing and creating merge/pull requests. All in bulk with scripts. The headings naturally wound up in this structure: Introduction Overview of steps Getting prepared Setup ssh keys Create your working directory Get an access token Download the whole codebase Cloning Pulling Make the changes A brief warning Another safety consideration Process example: [redacted] updates Process example: [redacted] updates Programmatically creating bulk pull requests Cleaning up Troubleshooting During git push More on reddit.com

https://documentation.divio.com/ is a good resource. More on reddit.com

No template to share per se, but I highly recommend some form of diagram like a Visio for al layers of your environment. I used to love the days I'd spend doing Visio diagrams of our environment at one job. I'd have layers upon layers showing the physical, logical, traffic flow, application and such aspects. People thought it was a little overkill until we'd have and outage or some other need to use them and it was amazing how quickly someone with zero familiarity could be brought up to speed on the lay of the land. A good visual goes a long way and can't be as easily misinterpreted as an email trying to describe things. More on reddit.com