Eleven Free Homelab Tools for the Questions Guides Skip

Every guide I write ends in the same handful of questions. How much hardware do I actually need? What happens when one box dies? Are my backups real or just a feeling? A guide can walk you through a setup, but it can't do arithmetic about your lab — so I built eleven small tools that can, at peira.dev/tools.

They're free, none ask who you are, and seven of the eleven keep working once the page has loaded — network unplugged, laptop in a cupboard, whatever.

They share one lab profile

This is the part that makes them a set rather than eleven unrelated pages. Describe your lab once — tick your services in the sizing calculator, press Save to profile — and the others pick it up. The failure simulator opens with your nodes already modelled; the backup planner knows what data you have; the power-loss playbook knows what's plugged in. Lab doc hands the whole thing back as a Markdown file.

Nothing about that profile leaves your browser. No account, no sync, no server that could leak it — which is also why it doesn't follow you between devices. The Markdown export is how you carry it elsewhere.

Plan the build

Sizing calculator — asks what you want to run and recommends nodes, RAM, and storage. It cares most about RAM, because that's the constraint that actually bites; vCPUs overcommit happily, memory doesn't. Tick "survive one node failure" and it insists on three nodes (a two-node cluster loses quorum the moment one dies).
Node failure simulator — kill a node and see which workloads fit on the survivors. It places the critical ones first and names the stranded ones.
3-2-1 backup planner — three copies, two devices, one offsite (the rule CISA recommends). It's blunt: a snapshot on the same disk as the original is versioning, not a backup.

Fix what's broken

The overlay network diagnostic is a decision tree born from a miserable afternoon: a container couldn't reach a machine across a Tailscale subnet router, and three layers had to be right — the route in the guest, the ACL grant, and a firewall on the destination. Two fail silently. The tool walks them in order.

Four more use a language model you point them at yourself (a Claude account, an API key for a provider you choose, or a model on your own hardware — the page calls it directly from your browser, nothing touches my site):

Log triage — paste the wall of output, get the one line that matters.
Compose review — reads a Docker Compose stack for what bites on the next update, reboot, or dead disk.
Explain before you run — paste a command from a forum reply, get a plain-English breakdown and a red/amber/green "can you undo it?".
The troubleshooter — describe the symptom, get ranked causes and the commands to check them.

A Docker fact I got wrong building the compose reviewer, since half the advice online is stale: since Docker 23.0, docker system prune --volumes and docker volume prune remove only anonymous volumes, and "unused" means no container attached at all — a stopped container still protects its volume. Named volumes need docker volume prune --all. The command that genuinely deletes named volumes is docker compose down -v. That's the one that eats a database.

Survive the bad day

Blast radius mapper — map dependencies, click to kill something, watch the cascade. The ranking is the useful part: it usually shows one unglamorous box (the switch, DNS, the container host) carrying most of the lab. Your recovery plan for that box is your recovery plan for everything.
Power-loss playbook — orders machines into shutdown waves (workloads, then compute, then storage, network last, because shutdown commands travel over it) and checks whether the sequence fits inside your battery, with an honest allowance for battery age. It'll generate matching NUT settings too.
Bus factor tool — the one I'd most like people to use. If you were unavailable for a month, could the people you live with get their photos back and keep the heating on? It asks nine questions and writes a letter for someone who has never used a terminal. It never asks for a password — it asks where the credentials are and who may open them.

What it costs and needs

Nothing, and not much. No accounts, no cookies, no analytics on the tool pages. Seven are single HTML files — save the page and they work offline. Four need a model you choose; if you paste a key it stays in your browser and goes only to the provider you picked. Every tool is also a public artifact you can fork, prompts included.

They're worksheets, not oracles. Each is a model of your lab, and a model is always simpler than the thing. Use them to find the question you should be asking, then verify on your actual hardware. The only real backup test is a restore; the only real UPS test is pulling the plug.