Folder sharing

What it is

Share exactly one host folder into a VM, live in both directions.

Give a FlashVM one host folder and it appears inside the VM at the path you choose. That folder is the only part of the host the VM can see. Changes on either side show up on the other instantly. Build output is the exception: node_modules, .venv and the target or build folders your .gitignore names stay on the VM’s own storage, so installs and builds run at full speed and never clutter your project.

Why it matters

Agents work on real projects. Folder sharing gives them the project and nothing else.

• One folder only. The VM sees exactly what you share.
• Live both ways. Files the VM writes land on the host at once.
• Build output stays in the VM. A 10,000-file node_modules installs and reads in 0.3 s on Apple silicon, faster than on the Mac’s own disk. Nothing to set up, for you or an AI agent.
• One flag. --share at creation.

Runs on

• Linux x86_64
• Linux arm64
• macOS
• Windows x64
• Windows arm64

How it works

Pass the host folder, a tag and the mount point inside the VM.

CLI

flash run --bundle /opt/flashvm/bundles/current --id vm1 --vcpus 1 --mem-mib 256 \
  --share host_dir=/home/me/project,tag=shared,at=/mnt/shared --entry 'sleep 3600' --detach
flash exec vm1 -- ls -l /mnt/shared

MCP

flash_resource(vm_id: "vm1", resource: "share")

API

GET /v1/flashvm/share
PUT /v1/flashvm/share
DELETE /v1/flashvm/share

The result

Your project’s changes are already on the host. Its build output stays in the VM.

A shared workspace with a hard wall around it.