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macOS VNC

Read this when you:

  • launch a managed AWS EC2 Mac desktop lease;
  • prepare an existing Mac for Crabbox VNC over provider: ssh;
  • debug Screen Sharing credentials or EC2 Mac Dedicated Host requirements.

Crabbox reaches macOS desktops two ways:

  • managed AWS EC2 Mac leases, provisioned onto an operator-allocated Dedicated Host;
  • static Macs you already own, reached through provider: ssh.

Both expose the desktop over Screen Sharing (Apple's VNC service) on the box's loopback 127.0.0.1:5900, and Crabbox tunnels that port to your machine over SSH. Nothing listens on a public VNC port.

Managed AWS EC2 Mac

crabbox warmup --provider aws --target macos --desktop --market on-demand
crabbox vnc --id silver-squid --open
crabbox screenshot --id silver-squid --output macos.png

Bootstrap behavior

When the lease comes up, Crabbox bootstraps the box for SSH and Screen Sharing:

  • enables Remote Login (SSH) for ec2-user and installs the per-lease public key;
  • generates a 16-character VNC password, sets it as the ec2-user account password, and stores it at /var/db/crabbox/vnc.password (mode 0600);
  • enables and starts com.apple.screensharing, bound to loopback and reached only through the SSH tunnel.

The default work root is /Users/ec2-user/crabbox, because the macOS system volume is read-only. crabbox vnc reads the stored password back over SSH and prints:

macos username: ec2-user
macos password: ...

Screenshots

crabbox screenshot --target macos captures the live Screen Sharing framebuffer over the same SSH-tunneled VNC connection (an RFB frame grab), the same surface WebVNC bridges. It does not shell out to screencapture, which is unreliable from a non-interactive EC2 Mac SSH session.

Instance types and the Dedicated Host

EC2 Mac instances run on Dedicated Hosts with AWS's 24-hour minimum host allocation period, so the lifecycle differs from regular Linux/Windows leases:

  • a macOS lease needs an allocated EC2 Mac Dedicated Host in the selected region;
  • capacity is On-Demand only — pass --market on-demand;
  • unless you set --type, Crabbox tries the current Apple silicon families in order (mac2.metal, mac2-m2.metal, mac2-m2pro.metal, mac-m4.metal, mac-m4pro.metal, mac-m4max.metal, mac2-m1ultra.metal, mac-m3ultra.metal) and finally mac1.metal;
  • to pin the lease to a specific host, set CRABBOX_HOST_ID or hostId in config. CRABBOX_AWS_MAC_HOST_ID and aws.macHostId remain accepted aliases.

crabbox warmup does not allocate a Dedicated Host implicitly. Trusted operators manage hosts explicitly:

crabbox admin hosts list      --provider aws --target macos --region eu-west-1
crabbox admin hosts offerings --provider aws --target macos --region eu-west-1 --type mac2.metal
crabbox admin hosts allocate  --provider aws --target macos --region eu-west-1 --type mac2.metal --dry-run
crabbox admin hosts allocate  --provider aws --target macos --region eu-west-1 --type mac2.metal --force
crabbox admin hosts release h-0123456789abcdef0 --provider aws --target macos --region eu-west-1 --force

Promoted AWS images are scoped by target, architecture, and region. Use crabbox image promote <ami-id> --target macos --region <aws-region> to promote a macOS AMI that was not created through crabbox image create.

Static Mac

A static Mac is an existing machine; Crabbox does not provision or manage it.

provider: ssh
target: macos
static:
  host: mac-studio.tailnet-name.ts.net
  user: alice
  port: "22"
  workRoot: /Users/alice/crabbox
crabbox vnc --provider ssh --target macos \
  --static-host mac-studio.tailnet-name.ts.net --host-managed --open

The Mac must already provide SSH, git, rsync, tar, and Screen Sharing (or another VNC-compatible service on 127.0.0.1:5900). Credentials stay host-managed — Crabbox does not set or read a password — so crabbox vnc prints credentials: host-managed and you log in with that Mac's own account or Screen Sharing password.

--open requires --host-managed, because opening the client lands you on that host's own OS login prompt rather than a Crabbox-created cloud desktop; the flag is your acknowledgement of that. Static Macs cannot be screenshotted with crabbox screenshot --target macos for the same reason — they are existing host machines, not Crabbox desktops.

Static Macs work well over Tailscale: put the MagicDNS name or 100.x address in static.host and keep Screen Sharing limited to trusted networks.

Troubleshooting

No host capacity (managed AWS). Use --market on-demand and confirm an EC2 Mac Dedicated Host is allocated in the region. Set CRABBOX_HOST_ID / hostId only to pin a specific host. Operators can inspect capacity:

crabbox admin hosts offerings --provider aws --target macos --region <region>
crabbox admin hosts quota     --provider aws --target macos --region <region>
crabbox admin hosts list      --provider aws --target macos --region <region>

target does not expose VNC on 127.0.0.1:5900. Screen Sharing is not listening on loopback yet. On a managed lease, wait for bootstrap to finish; on a static Mac, enable Screen Sharing and confirm it binds 127.0.0.1:5900.

VNC prompts for host credentials. If the output shows managed: false, you opened a static Mac — use that host's own Screen Sharing credentials. Managed EC2 Mac leases print the generated ec2-user password.

Related docs: