Run GPU experiments on vast.ai

You rent a GPU instance with the native vastai CLI, wait for it with vastai-connect (which writes an SSH alias), then work with plain ssh/rsync. Money is spent per hour from the moment an instance is created until it is destroyed. Never leave one behind.

Prerequisites (check once)

vastai show instances --raw   # errors if vastai isn't installed or the API key isn't set

If missing: have the user register a public SSH key and create an API key at https://cloud.vast.ai/manage-keys/, then:

uv tool install vastai && vastai set api-key <key>
uv tool install git+https://github.com/Yusuke710/vastai-skill.git

1. Find and rent

# Cheapest matching offers first. GPU names use underscores: RTX_3060, RTX_4090, A100_SXM4...
vastai search offers 'gpu_name=RTX_3060 num_gpus=1 reliability>0.98 dph<0.45' -o 'dph' --raw

vastai create instance <offer_id> --image vastai/pytorch:latest --disk 30 --ssh --raw
# → {"success": true, "new_contract": <instance_id>}

• Sanity-check the offer's dph_total ($/hr) against what the task deserves before renting.
• Image: default to vastai/pytorch:latest — its CUDA base layers are cached on most vast.ai hosts (boot-to-SSH ≈ 2–3 min). Other images usually download cold.
• --disk cannot be resized later; size it for datasets + checkpoints.
• The new_contract value is your instance id — the only instance you own.
• Running several instances? vastai label instance <id> <name> and use a distinct --alias for each.

2. Wait until reachable

vastai-connect <instance_id> --alias vast-gpu  # blocks until SSH works; then `ssh vast-gpu` / rsync work

Typical wait is 1–3 minutes. On timeout (5 min default) or any stall later (crawling downloads, broken SSH auth): destroy and rent a different offer — re-renting beats debugging. Cheap consumer hosts are a lottery; datacenter GPUs (A100/H100) are usually more reliable.

3. Work over plain ssh/rsync

Normal remote-Linux workflow from here — nothing vast.ai-specific. Reminders, not recipes:

• rsync the project over gitignore-filtered so junk (.venv, data) doesn't cross the wire.
• Sanity-check that torch actually sees the GPU before paying for a long run.
• Detach long jobs so they survive SSH drops, and capture the exit code.
• Before destroying, pull back artifacts worth keeping (weights, logs, results) — they exist only on the instance. Check with the user if unsure what to keep.

4. Destroy the instance

vastai destroy instance <instance_id>
vastai show instances --raw              # verify it's gone; [] means nothing is billing

• Destroy, never stop — stopped instances still bill storage and may be unable to restart.
• Only destroy instance ids you created in this session (the new_contract values you received). Other instances — even ones with a familiar label or the same image — may belong to another job or agent running in parallel. Report unknown instances to the user; never "clean them up".
• If you intentionally leave an instance running (e.g. a long training job), tell the user explicitly: instance id, $/hr, and how to destroy it.