persistence-migration

NixOS impermanence activation fails with 'target is busy' when existing mount points conflict with new path structures, such as splitting a persisted directory into subdirectories or converting a file into a directory. The migration workflow resolves this by detaching old mounts and removing blocking targets before re-running activation.

To safely migrate impermanence path layouts from a directory to individual files, run the defined migration workflow: inspect the current mounts, stop child mounts, detach the old parent mount, remove blocking targets, and re-run system activation to verify the new persistence setup.

Detaching an old parent mount before stopping child mounts risks data loss and activation errors. Safe impermanence migration requires stopping child mounts first to cleanly detach the parent and reconfigure the persistence layout without conflicts.

Fix 'A file already exists' errors during NixOS system activation by removing blocking targets that conflict with the new persistence layout. The migration workflow inspects mounts, detaches the old structure, clears the blocking file or directory, and re-runs activation.

You need an impermanence mount migration workflow when changing persisted path layouts, such as splitting a directory into subpaths, breaking a directory into individual files, or changing a persisted file into a directory, which causes mounting conflicts during activation.

You can convert a persisted file into a directory safely by using a migration workflow that stops child mounts, detaches the old mount, removes the blocking file target, and re-runs activation to apply and verify the new mount configuration.