FSDB(8) MidnightBSD System Manager’s Manual FSDB(8)


fsdb — FFS debugging/editing tool


fsdb [−d] [−f] [−r] fsname


The fsdb utility opens fsname (usually a raw disk partition) and runs a command loop allowing manipulation of the file system’s inode data. You are prompted to enter a command with fsdb (inum X)> where X is the currently selected i-number. The initial selected inode is the root of the file system (i-number 2). The command processor uses the editline(3) library, so you can use command line editing to reduce typing if desired. When you exit the command loop, the file system superblock is marked dirty and any buffered blocks are written to the file system.

The following options are available:


Enable additional debugging output (which comes primarily from fsck(8)-derived code).


Left for historical reasons and has no meaning.


Open the file system read/only, and disables all commands that would write to it.


Besides the built-in editline(3) commands, fsdb supports these commands:


Print out the list of accepted commands.

inode i-number

Select inode i-number as the new current inode.


Revert to the previously current inode.

clri i-number

Clear i-number.

lookup name

Find name in the current directory and make its inode the current inode. Name may be a multi-component name or may begin with slash to indicate that the root inode should be used to start the lookup. If some component along the pathname is not found, the last valid directory encountered is left as the active inode. This command is valid only if the starting inode is a directory.


Print out the active inode.


Print out the block list of the active inode. Note that the printout can become long for large files, since all indirect block pointers will also be printed.


Increment the active inode’s link count.


Decrement the active inode’s link count.

linkcount number

Set the active inode’s link count to number.


List the current inode’s directory entries. This command is valid only if the current inode is a directory.

rm name

Remove the entry name from the current directory inode. This command is valid only if the current inode is a directory.

ln ino name

Create a link to inode ino under the name name in the current directory inode. This command is valid only if the current inode is a directory.

chinum dirslot inum

Change the i-number in directory entry dirslot to inum.

chname dirslot name

Change the name in directory entry dirslot to name. This command cannot expand a directory entry. You can only rename an entry if the name will fit into the existing directory slot.

chtype type

Change the type of the current inode to type. Type may be one of: file, dir, socket, or fifo.

chmod mode

Change the mode bits of the current inode to mode. You cannot change the file type with this subcommand; use chtype to do that.

chflags flags

Change the file flags of the current inode to flags.

chown uid

Change the owner of the current inode to uid.

chgrp gid

Change the group of the current inode to gid.

chgen gen

Change the generation number of the current inode to gen.

mtime time

Change the modification, change, or access time (respectively) on the current inode to time. Time should be in the format YYYYMMDDHHMMSS[.nsec] where nsec is an optional nanosecond specification. If no nanoseconds are specified, the mtimensec, ctimensec, or atimensec field will be set to zero.

quit, q, exit, <EOF>

Exit the program.


editline(3), fs(5), clri(8), fsck(8)


The fsdb utility uses the source code for fsck(8) to implement most of the file system manipulation code. The remainder of fsdb first appeared in NetBSD, written by John T. Kohl.

Peter Wemm ported it to FreeBSD.


Manipulation of ‘‘short’’ symlinks has no effect. In particular, one should not try changing a symlink’s type.

You must specify modes as numbers rather than symbolic names.

There are a bunch of other things that you might want to do which fsdb does not implement.


Use this tool with extreme caution--you can damage an FFS file system beyond what fsck(8) can repair.

MidnightBSD 0.3 September 14, 1995 MidnightBSD 0.3