resize_lfs —
resize a mounted log-structured filesystem
  
    | resize_lfs | [ -v] [-snew-size]
      mounted-file-system | 
resize_lfs grows or shrinks a mounted log-structured
  filesystem to the specified size. mounted-file-system is
  the name of the filesystem to be resized, and new-size
  is the desired new filesystem size, in sectors. If
  new-size is not specified,
  resize_lfs will default to the current size of the
  partition containing the filesystem in question.
When growing, the partition must be large enough to contain a
    filesystem of the specified size; when shrinking,
    resize_lfs must first “clean” the
    segments that will be invalid when the filesystem is shrunk. If this
    cleaning process results in these segments becoming redirtied, this
    indicates that the given new size is not large enough to contain the
    existing filesystem data, and resize_lfs will return
    an error.
To resize the file system mounted at /home to 32576
  sectors:
resize_lfs -s 32576
  /home
The resize_lfs command first appeared in
  NetBSD 3.0.
Konrad Schroder ⟨perseant@NetBSD.org⟩
resize_lfs should be able to resize an unmounted
  filesystem as well.