freebsd man page for dumpfs

DUMPFS(8)						    BSD System Manager's Manual 						 DUMPFS(8)

NAME
     dumpfs -- dump UFS file system information

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

DESCRIPTION
     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 percentage.

     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).

SEE ALSO
     disktab(5), fs(5), disklabel(8), fsck(8), newfs(8), tunefs(8)

HISTORY
     The dumpfs utility appeared in 4.2BSD.

BSD
								   May 16, 2013 							       BSD