Protecting an image
Put an instance's disk in an encrypted container, so a copy of the file is useless.
On this page 3 sections
msl protect <instance>
msl unprotect <instance>Moves the instance's disk into an encrypted container. A copy of the file — on a USB stick, in a backup, in a support upload — is then useless on any other Mac.
What it costs#
A real copy of the whole disk, because MSL's instant-copy trick cannot cross into a container. Minutes for a large instance, and that much free space while it runs. Opening it at start is well under a second.
The original is removed only after the copy inside has been read back and checked, so there is no moment where both are gone.
What it does and does not buy#
| Closed | Still open |
|---|---|
| Dragging the disk to a USB stick, AirDrop, email | Anything inside the instance, to anyone who can open a shell in it |
| Time Machine and every backup service copying it in the clear | An administrator of this Mac, who can reach the key |
A guest copying it out of /mnt/mac |
That last one is worth its own sentence. The Mac's home folder is shared into every instance, writable, and instance disks live inside it — so any Linux terminal can copy any instance's disk unless you deny sharing.macHome. msl doctor says so if you have asked for an image to be protected and left that open.
Protection is a consequence, not a switch
Deny instance.clone or shipment.export for an instance and MSL treats it as one you mean to keep uncopyable, and reports anything still open.
A key only you hold#
msl vault <instance> status | adopt | unlock | lockBy default the key is derived from a secret on this Mac, which closes every accidental route but not a determined administrator of it. Adopt moves the container to a passphrase you type instead. After that nothing on the Mac can open it until somebody supplies it, including MSL after a reboot.
Saved memory from hibernating goes inside the container too. A .state file is the guest's whole RAM, and encrypting the disk while leaving that beside it in the clear would protect very little.