impermanence.nix

        # Function to create a directory in both the place where we want
        # to bind mount it as well as making sure it exists in the location
        # where persistence is located. This also enforces the correct ownership
        # of the directory structure.
        mkDirCreationSnippet = persistentStoragePath: dir:
        ''
            # capture the nix vars into bash to avoid escape hell
            local sourceBase="${persistentStoragePath}"
            local target="${dir}"
            # iterate over each part of the target path
            local previousPath=""
            for pathPart in $(echo "$target" | tr "/" " "); do
              # construct the incremental path, e.g. /var, /var/lib, /var/lib/iwd
              local currentTargetPath="/$previousPart/$pathPart"
              # construct the source path, e.g. /state/var, /state/var/lib
              local currentSourcePath="$sourceBase$currentTargetPath"
              if [ ! -e "$currentSourcePath" ]; then
                printf "Bind source '%s' does not exist, creating it
                mkdir "$currentSourcePath"
              fi
              if [ ! -e "$currentTargetPath" ]; then
                mkdir "$currentTargetPath"
              fi
              # synchronize perms between the two, should be a noop if they were
              # both just created.
              chown -c --reference="$currentSourcePath" "$currentTargetPath"
              unset currentSourcePath
              unset currentTargetPath
            done
            unset sourceBase
            unset target
          '';