Snapshots
Save a machine's state under a name and go back to it — and the one rule that keeps it safe.
On this page 4 sections
A snapshot saves a machine's state — everything in its memory, every running program — under a name, so you can return to that exact moment.
Saving one#
- The instance has to be running or suspended — a stopped one has no memory to save. (The card says "Start name to take a snapshot.")
- Type a name in New snapshot name — letters, digits, hyphens and underscores, like
before-upgrade. - Click Save (or press Return).
Restoring one#
Click Restore beside it. Whatever the instance is doing is replaced — it stops if it was running — and it comes back exactly as it was when you saved. As the card says: restoring discards everything since.
The rule that keeps it safe#
For "undo" after changing files, a copy of those files is often the better tool. For the disk as a whole, Repair Disk keeps a real copy of the disk before it changes anything.
Where they live#
Each snapshot is a file in ~/Library/Application Support/MSL, named vm-<instance>-<snapshot>.state, about the size of the instance's memory. There's no delete button yet; removing the instance deletes all of its snapshots. See Reclaiming disk space.