Copy-on-write makes snapshots fast and accessible, but deleting them to reclaim disk space can be a bit confusing. Let’s have a quick primer on how those work, and look at a small utility to help reason about it.

zsnapfree is a TUI for showing how much space can be reclaimed by freeing zfs snapshots. It is a TUI wrapper over the standard zfs tool.

If you just want to see zsnapfree in action, skip to the screencast.