macOS desktop sandboxes

A macOS desktop sandbox gives you a temporary Mac window for opening apps, testing installers, and working with files without changing your everyday system. This preview runs locally on an Apple Silicon Mac.

Prepare this Mac

Install the tested desktop runtime and check that it is ready:

celesto setup --macos
celesto doctor --backend vz

You need an Apple Silicon Mac running macOS 14 or newer. The image folder must be on an APFS volume, the normal file system used by modern Macs.

Create and open a desktop

The first sandbox prepares macOS from an Apple restore file. Celesto asks before downloading it because preparation needs about 50 GB of free space and can take 20–40 minutes. A progress bar follows the download, macOS installation, and desktop setup phases. If installation fails after the download finishes, the next attempt reuses that restore file instead of downloading it again.

celesto sandbox create --os macos --name test-mac
# Next: celesto sandbox desktop test-mac

Open the desktop:

celesto sandbox desktop test-mac

Celesto opens the built-in Screen Sharing app. The connection stays on this Mac and uses a temporary password that is not printed.

Copy and paste

Copy and paste works in both directions between your Mac and the sandbox desktop. Copy on one side, paste on the other.

Anything you copy on your Mac is readable inside the sandbox while it runs. If you would rather keep the two clipboards separate, turn it off when you create the sandbox:

celesto sandbox create --os macos --name private-mac --no-clipboard

The choice is saved with the sandbox, so stopping and starting it keeps the same setting.

Share files

Add one local folder when you create the sandbox:

celesto sandbox create --os macos --name shared-mac --mount "$PWD"

The folder is read-only unless you add --writable-mounts. Use Finder inside the sandbox to open the shared folder.

Install and use apps

Inside the desktop, macOS works normally. You can open a downloaded .dmg, drag an app into Applications, respond to permission prompts, and restart the sandbox when an installer requires it. Celesto does not turn off System Integrity Protection, Gatekeeper, or macOS permission prompts.

Stop the sandbox when you are done for now:

celesto sandbox stop test-mac

Delete it to discard its private disk:

celesto sandbox delete test-mac

The reusable base image remains, so creating the next sandbox is much faster. Remove that image separately with celesto image rm macos-latest.

Prepare an image ahead of time

You can perform the long preparation step before creating a sandbox:

celesto image build --os macos --ipsw latest -t macos-latest

The restore file comes from Apple and the finished image stays on this Mac. Celesto does not support saving, loading, or publishing macOS images.

Preview limits

• Only Apple Silicon hosts are supported.
• Each preview sandbox uses 4 CPU cores, 8 GB of memory, and an 80 GB logical disk; custom resource sizes are not enabled yet.
• At most two macOS sandboxes can run at once.
• Shell, exec, file transfer, and SSH tunnels are not enabled for macOS guests in this preview; desktop access works independently.
• Bridge networking, outbound-domain rules, pause and resume, snapshots, and browser sessions are not supported for macOS guests yet.
• The base image and each sandbox are tied to the local Mac. Review Apple's current software license agreements and use hardware you own or control for permitted development and testing.

Implementation notes: macOS image ownership is in src/celesto/macos/images.py, runtime translation is in src/celesto/macos/lume.py, and lifecycle integration is covered by tests/test_vm_macos.py and tests/test_runtime_vz.py.