Creates an instant, space-efficient snapshot (point-in-time copy) of the /home subvolume at /backup/home-snapshot, and -r makes it read-only, which is required before sending it elsewhere. Snapshots share data with the original until files change, so they cost almost nothing at creation. Related: btrfs send moves it off-box.
Looking for more? Search all 7,657 commands — works offline, in English or Spanish, and fixes typos.