Command Section
DUMPFS(8)               FreeBSD System Manager's Manual              DUMPFS(8)

     dumpfs - dump UFS file system information

     dumpfs [-f] [-l] [-m] filesys | device

     The dumpfs utility prints out the UFS super block and cylinder group
     information for the file system or special device specified, unless the
     -f, -l or -m flag is specified.  The listing is very long and detailed.
     This command is useful mostly for finding out certain file system
     information such as the file system block size and minimum free space

     If -f is specified, a sorted list of all free fragments and free fragment
     ranges, as represented in cylinder group block free lists, is printed.
     If the flag is specified twice, contiguous free fragments are not
     collapsed into ranges and instead printed in a simple list.  Fragment
     numbers may be converted to raw byte offsets by multiplying by the
     fragment size, which may be useful when recovering deleted data.

     If -l is specified, the pathname to the file system's container derived
     from its unique identifier is printed.

     If -m is specified, a newfs(8) command is printed that can be used to
     generate a new file system with equivalent settings.  Please note that
     newfs(8) options -E, -R, -S, and -T are not handled and -p is not useful
     in this case so is omitted.  Newfs(8) options -n and -r are neither
     checked for nor output but should be.  The -r flag is needed if the
     filesystem uses gjournal(8).

     fs(5), fsck(8), gpart(8), newfs(8), tunefs(8)

     The dumpfs utility appeared in 4.2BSD.

FreeBSD 11.1-RELEASE-p4          May 16, 2013          FreeBSD 11.1-RELEASE-p4
Command Section