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Man Pages

Manual Reference Pages  -  FSDB (8)


fsdb - FFS debugging/editing tool


See Also


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:
-d Enable additional debugging output (which comes primarily from fsck 8 -derived code).
-f Left for historical reasons and has no meaning.
-r 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:

help Print out the list of accepted commands.

inode i-number
  Select inode i-number as the new current inode.

back Revert to the previously current inode.

clri i-number
  Clear i-number.

lookup name
cd 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.

findblk disk_block_number ...
  Find the inode(s) owning the specified disk block(s) number(s). Note that these are not absolute disk blocks numbers, but offsets from the start of the partition.

  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.

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

rm name
del 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.

btime time
mtime time
ctime time
atime time
  Change the creation (birth), 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 birthnsec, mtimensec, ctimensec, or atimensec field will be set to zero. Note that btime is available on UFS2 file systems only.

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
.Nx , written by
.An John T. Kohl .

.An Peter Wemm ported it to
.Fx .


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.
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